: Cylinder Head Info!



customGTP
01-23-06, 09:13 PM
I picked up two sets of heads a few months ago. One set is the old style and the other is the roller rockerstyle for the cams. Anyone know what year they changed designs and what the gains were from the change of designs?

BECAUSE

I'm going to take the heads to a proformance shop here in town and have them flowed and documented. Then Im gonna port them and have them flowed again.

Any ideas and info great appreciated

eldorado1
01-23-06, 11:39 PM
The 99 and earlier were the direct acting cams. The 2000+ are the roller cams. Basically they did it for better gas mileage, they might have picked up a couple horses due to less frictional losses. I don't remember what the 2000s are spec'd at.

zonie77
01-24-06, 02:14 AM
Do you have info on porting?

dkozloski
01-24-06, 02:41 AM
With engines in general, the adoption of roller cam followers allowed the change to 5W-30 oil and the resulting better gas milage because that was the last sliding high pressure contact in engines that gave wear problems at starup.

Ranger
01-24-06, 03:18 PM
Koz,
Do you think that 5w30 vs 10w30 will produce enough of a milage gain to be seen without instrumentation? My personal opinion is no. Your thoughts? Remember, we're talking reality vs theory. I have yet to do an oil change on my '02 but I am seriously considering sticking with 10w30.

zonie77
01-24-06, 04:13 PM
From what I've read, most of the benefit of 5w to 10w is cold start pumpup. Mileage benefit is secondary but with CAFE standards every little bit helps. If several small improvements can get you to the next mpg (18 instead of 17) it's worth it.

dkozloski
01-24-06, 04:16 PM
I wasn't stating an opinion but rather an engineers report. GM made the tests and decided that the increased mechanical complexity was worth the tradeoff. It sounds iffy to me too but the manufacturers have really been under the gun to increase CAFE milage and every little bit helps. Or so said the little old lady as she peed in the ocean.

jadcock
01-24-06, 04:46 PM
The main design change with the 2000+ design is to be able to run 87 octane fuel. The 2000+ engines have a 10.0:1 compression ratio, vs. 10.3:1 for the 1999 and older engines. The newer heads have a faster burn combustion chamber and port design, and will probably allow for slightly better mileage, as stated. Probably nothing you'll notice. The EPA ratings didn't change that I know of.

Ranger
01-24-06, 10:25 PM
I wasn't stating an opinion but rather an engineers report. GM made the tests and decided that the increased mechanical complexity was worth the tradeoff. It sounds iffy to me too but the manufacturers have really been under the gun to increase CAFE milage and every little bit helps. Or so said the little old lady as she peed in the ocean.
I realize what you were stating. I was just wondering what your opinion was. I think I once asked "Rob" this same question and as I recall he said it would be negligable. Think I'll stick with 10w30.

jadcock
01-25-06, 08:49 AM
I think dkozloski was referring to the roller cam follows as fuel economy improvers, not the actual weight of oil. Under most conditions, there will be no measurable economy differences in using 5W-30 vs. 10W-30, since both oils are nominally a 30 weight when warm. The 5W-30 will provide a startup benefit, but not much else. In fact, many people in other vehicles who use 5W-20 vs. 5W-30 don't see much if any fuel economy gain.

eldorado1
01-25-06, 11:46 AM
I think dkozloski was referring to the roller cam follows as fuel economy improvers, not the actual weight of oil. Under most conditions, there will be no measurable economy differences in using 5W-30 vs. 10W-30, since both oils are nominally a 30 weight when warm. The 5W-30 will provide a startup benefit, but not much else. In fact, many people in other vehicles who use 5W-20 vs. 5W-30 don't see much if any fuel economy gain.

exactly, using roller cams eliminates a high pressure/high wear point that necessitated 10W-30. The less friction itself, and not the oil, causes the better fuel economy.

jadcock
01-25-06, 03:13 PM
But even then, I don't think it's that much. It doesn't show up in the EPA rating does it? It was 17/26 through 2003, right? I get 21/30 with my '97 model, and that's with the non-roller cam followers.

eldorado1
01-25-06, 04:28 PM
But even then, I don't think it's that much. It doesn't show up in the EPA rating does it? It was 17/26 through 2003, right? I get 21/30 with my '97 model, and that's with the non-roller cam followers.

both 99 and 00 are rated 17/26.

AutoGeek
01-25-06, 11:29 PM
I may be wrong about this but the biggest benefit to a roller cam and follower setup is that you can run more aggressive and higher lift lobes on the cam without excessive wear to the lobes. Second would be more HP and if I gave a rip more MPG.

Reactor
01-26-06, 10:22 AM
Rollers let the engine run and much higher RPMs without lifters floating. this is important if at redline alot, like if racing.

jadcock
01-26-06, 10:29 AM
Yes, you CAN use more aggressive cam profiles with rollers. Cadillac didn't on the 2000+ engines, but I suppose they could have. The valve springs have more to do with valvetrain float at high RPM than the lifter design.

customGTP
01-26-06, 11:17 AM
The 2000+ engines have a 10.0:1 compression ratio, vs. 10.3:1 for the 1999 and older engines.

Now...... I have a 98 motor and wanna put on the 00 heads so I can get a decent set of cams on a running motor by spring. What do I have to change to get the 98 motor to the 00 compression? Cause when I autocross this comespring im gonna be revving the piss out of the motor to get the topend power :)
thanx for the lesson thus far

dkozloski
01-26-06, 02:49 PM
There are differences in valve train geometry between roller and sliding lifters so there is a possibility of slightly more aggressive cam profiles possible with roller followers. Probably more theoretical than real.

jadcock
01-26-06, 04:38 PM
Now...... I have a 98 motor and wanna put on the 00 heads so I can get a decent set of cams on a running motor by spring. What do I have to change to get the 98 motor to the 00 compression? Cause when I autocross this comespring im gonna be revving the piss out of the motor to get the topend power :)

I don't know if the pistons themselves are also different, or just a slightly larger combustion chamber on the heads. I assume you know that a '98 computer won't work with 2000+ cylinder heads, but it won't work with really aggressive cams either, so you'll have to write your own code anyway.

eldorado1
01-26-06, 05:13 PM
I assume you know that a '98 computer won't work with 2000+ cylinder heads

Actually, it should. You might have to install a stud on the "rear" exhaust cam gear and a reluctor if there isn't one already, but it should work. You can't use the COP system of course,

zonie77
01-26-06, 07:34 PM
I don't know if the combustion chamber size is in the manual but it's not something thrown around like SBC heads. I'd CC the heads and see if they are real close.

customGTP
01-26-06, 07:41 PM
You can't use the COP system of course, whats that?

Also.. I'm using the Holley Commander 950 harness computer so I can do anything lol

So theoretically they will work? or no

eldorado1
01-26-06, 08:02 PM
whats that?

Also.. I'm using the Holley Commander 950 harness computer so I can do anything lol

So theoretically they will work? or no

Coil-on-plug. Since you would be using the pre-99 block, you can reuse the pre-99 ignition module and coil packs. Assuming the cam chains line up, and the heads physically bolt on (I'm told they do), it should work just fine.

If it has a cam sensor, then it might be plug and play.

jadcock
01-27-06, 09:56 AM
Actually, it should. You might have to install a stud on the "rear" exhaust cam gear and a reluctor if there isn't one already, but it should work. You can't use the COP system of course,

I think there will be tuning differences due to the different camshafts and compression ratio. It sounds like it's a moot point, though, as he's using an aftermarket controller.

customGTP
01-28-06, 10:54 AM
im pretty sureit has a cam sensor, so I hope everything works out cause im gonna toss em on there once they are done.

JaxxMan
03-24-06, 09:26 PM
Just found this thread, I was also wondering about the 2000-03 head swap with an older N*.

Anyone have some pics to show what the roller design looks like ?

TIA Jaxx

eldorado1
03-24-06, 09:49 PM
I don't think it would be a problem, but it would be a lot of work. Need different exhaust manifolds, intake, *possibly* crossover.

Ranger
03-24-06, 10:16 PM
Just found this thread, I was also wondering about the 2000-03 head swap with an older N*.

Anyone have some pics to show what the roller design looks like ?

TIA Jaxx

http://caddyinfo.ipbhost.com/index.php?act=Attach&type=post&id=2374

JaxxMan
03-24-06, 10:58 PM
Thx Ranger that a great photo!
I know certain mods will be required, I'm still in the investigation phase but I think the intake could be kept stock. New manifold spacers can be made to bridge the gap.

I have a friend that built a mini foundry for casting aluminum parts and have lots of CNC machining contacts.

Thx again Jaxx

JaxxMan
03-25-06, 12:25 AM
Ranger
Is the roller design exclusively in the 2000 to 2003 L37 model ?
I ask because I won some heads on eBay and just got them.
They are the direct lifter to cam design and the seller is claiming they are from a 2002 motor.

Is there number on the casting that can verify it's age ?
Thx again Jaxx

Ranger
03-25-06, 01:30 AM
I do not know numbers, but if it is flat tappet (not roller follower) it is pre 2000.

eldorado1
03-25-06, 08:34 AM
Is there number on the casting that can verify it's age ?
Thx again Jaxx

Usually there is a kind of star looking stamp with two numbers in it for the year. (i.e. '96 or '00)

JaxxMan
03-25-06, 12:29 PM
I thought that might be the case, this must be a 1998 head then.
Sorry for the bad qualty pic, PDA camera. I can't find the cable for my other camera.

eldorado1
03-25-06, 02:58 PM
I thought that might be the case, this must be a 1998 head then.
Sorry for the bad qualty pic, PDA camera. I can't find the cable for my other camera.

Yep, that's a 98. I don't know if that means manufacturing year or model year though. In other words, it could be from a '99 car that was made in 98.

customGTP
03-25-06, 08:46 PM
well I talked to my Cadillac dealer tech about this a few weeks back.. he said they wouldnt work... forgot the reasoning though. Anyways.. ill be getting cams lifters retainers and bigger injectors for my GP soon:)

also check out my new thread !!

eldorado1
03-25-06, 09:07 PM
well I talked to my Cadillac dealer tech about this a few weeks back.. he said they wouldnt work...

I'd like to hear why. They should be a direct swap, but since I haven't done it, I can't say for certain that it would work.

chevelle
03-25-06, 11:14 PM
There is quite a bit of misinformation so far in this post. Hopefully the following will clear the air.


1993-1999 Northstars used cylinder heads with rubbing element, direct acting flat tappets. The 2000 and later Northstar engines have cylinder heads redesigned for roller finger followers and stationary hydraulic lash adjusters.

The heads will not interchange. You cannot (practically) put the later model heads on earlier engines and you cannot put earlier heads on later model engines...i.e...the flat tappet heads and the roller follower heads will not interchange.

Roller followers were incorporated on the 2000 model year cylinder heads primarily for friction reduction thus leading to a fuel economy increase. The direct acting tappets (93-99) cause quite a bit of friction opening and closing 32 rubbing elements. The rollers eleminate this friction causing a significant fuel economy gain. This is significant in terms of the EPA test but probably not as significant in the real world.

The roller followers become an enabler for the change to 5W30 oil from the 10W30 required on 93-99 engines. The thinner oil results in an additional fuel economy improvement due to the lower viscous drag in bearings and on other moving surfaces. This is also a minor gain but significant when viewed across the entire vehicle fleet on the road.

The rollers were not implemented just for the 5W30 oil. They were implemented for the fuel economy improvement they, themselves cause. The rubbing element lifters in the earlier engines are more reliant on the hydrodynamic bearing film formation to prevent wear and thus need the heavier viscosity of the 10W30 to maintain an adequate bearing film thickness under all conditions.

The rollers are an additional enabler in that they also allow longer oil change intervals. The rollers are far more tolerant of depleted oil and actually deplete the antiwear additives in the oil less due to the lower rubbing friction surfaces. This is a secondary item not the primary reason for the rollers. The oil life monitor for the 2000 and later engines was recalibrated and revalidated for 12,500 maximum change intervals (under optimum conditions of course...your results may vary and short trip driving results in significantly lower mileage change intervals) because of the roller elements.

The "best" heads for performance would be the earlier 39-99 heads in terms of port flows. The 2000 and later heads are a bit deficient in the exhaust valve size and exhaust port flow if performance is the main consideration.

There were several goals for the 2000 model redesign. First and formost was to meet the very very tight LEV emission standards. This had not been done on a large, luxury car at that time and had not been done on a V8 at that time. The exhaust valve sizing and exhaust port shape and volume were optimized for emissions and not performance necessarily. High gas flow velocity and catalytic converter lightoff were primary concerns with the LEV standards and performance had to be penalized sligthly to achieve those results.

Another goal was to change the fuel octane requirements from premium to regular. In that vein the combustion chamber was redesigned for faster burn and the compression was lowered slightly to aid in the octane reduction requirements. All in all, this was accomplished without any LOSS in power which was an acheivement in itself.

The valve could care less whether the cam is a roller or flat follower in terms of lift or performance. It just doesn't matter. The key to performance is the lift profile of the valve. Given a specific lift profile for the valve a flat tappet cam or a roller cam can be designed to provide that life profile. The actual, physical cam profiles you see would look different but act the same on the valve. A roller cam requires a different profile simply to "be the same" as a flat tappet. Just geometry. There is no inherent performance potential in a roller cam profile.

It is not really practical to compare the application of roller followers in over head cam engines and pushrod engines. The applications bring significant operational differences into play that make the comparision much like apples and oranges. What you hear generically about rollers (in pushrod engines) does NOT necessarily apply to rollers in overhead cam engines.

With any engine using poppet valves the ideal would be to instantly open the valves, hold them open and close them instantly for best performance...the perverbial square cam lobe would do this...LOL. You cannot do that, however. So the cam lobe is designed to accelerate the valve open, slow it down, hold it open, acclerate the valve closed, slow it down and set it on the seat without the cam follower ever leaving the cam lobe. "No follow" is death to the valve train so the cam follower MUST always stay on the cam lobe. The force that keeps the cam follower on the lobe is the valve spring. So....the starting point for any cam profile is the valve spring and the load it imposes. The limit for valve spring loads is the amount of load the cam lobe/lifter interface can handle without wearing out. Flat tappet cams have lower load limits than roller cams.

Most all flat tappet cams are made of cost effective and very wear resistant cast iron. Putting a roller follower into the system instantly increases the load at the cam lobe interface due to the reduced contact area of the roller. Just to change to a roller (no heavier springs or anything else changed) the cam must be made of heat treated steel to handle the inherent additional contact loading of a roller.

Roller lifters were incorporated into pushrod engines back in the mid 80s purely for friction reduction and fuel economy. Reducing the rubbing friction in the flat tappet pushrod engines was worth about 0.5 MPG on the EPA fuel economy test. While the change to rollers was expensive it was "cheap fuel economy". Originally, the roller cam profiles simply emulated the earlier flat tappet cam lift profiles AS MEASURED AT THE VALVE. If you happen to look at a 1988 4.5 roller cam and a 1987 flat tappet cam from the 4.1/4.5/4.9 pushrod engines the cams look very different but that actuate the valve with the exact same lift profile. The roller follower requires the "fatter" lobe due to the geometry of the roller. There is no difference to the valve.

Evolution then took place. The roller systems required the steel cams to handle the added contact pressure of the roller followers even with the same old valve springs as used before. Fortunately, the steel cams not only met the load bearing requirements but ADDED a substantial additional load bearing capability. So....heavier and heavier valve springs could be used without wearing the cam out. With heavier valve springs a more aggressive cam profile could be designed resulting in greater performance.

This is the fundamental reason that roller cams are associated with performance. Racers knew for a long time that roller cams could handle huge spring loads allowing very aggressive cam profiles and ultra high RPM operation. But the roller systems were costly and HP alone would not provide the impetus for roller systems in production engines. EPA mandated fuel economy requirements, however, did dictate rollers. Now that the rollers were in place the system became an enabler for huge performance improvements. This ultimately lead to the LS7 engine that makes 505 HP and can rev past 7000 RPM reliably with pushrods.

Simply putting roller followers in an engine will not make more HP and does not allow a more aggressive cam profile without other changes...such as the heavier valve springs. Rollers ARE an enabler for HP as they can handle stronger valve springs which become the enabler for the real power increase due to the more aggresive valve lift profile.

Roller followers were used for ages in diesel engines due to the degraded lubrication in diesels (soot in the oil). They are not needed for friction or performance in those applications....just for depleted oil durability.

The incorporation of a roller cam in an engine can actually cause a LOSS in power. As mentioned, the roller cam profile looks quite a bit different from the "same" flat tappet cam valve lift profile. There are often cases where a valve lift profile used on a flat tappet cam , when converted to a roller cam lobe profile, will result in a lobe with a "hollow" or "dip" in the lobe surface between the opening lift and the peak lift. If you lay a straight edge across the flank of the lobe you can actually see daylight under the straight edge in the middle of the lift. These are called "inverse flank cams" or "hollow lobes" among other things. Manufacturing engines have very bad names for them. To gring those cams requires a VERY small diameter grinding wheel to get down into the convex surface of the cam lobe. Typical cam grinding wheels are about 3 to 4 feet in diameter. "Inverse cams" require a 3 or 4 INCH grinding wheel. So, it is very unusual to see inverse grind cam lobes in high volume production. There are cases where engines actually lost power when roller cams were installed for fuel economy because the previously used cam profile resulted in a inverse cam lobe when converted. As a result, the valve lift profile was detuned to eliminate the inverse lobe requirement. Inverse cams work great for performance so many of the high performance hot rod roller cams in race engines have inverse designs. The LS7 has a specialty low volume cam with inverse lobe flanks due to the very aggressive cam profile in that engine.

One way that pushrod engines and overhead cam engines differ that is not so apparent is the amount of actual valve train mass and the inertia of the system. A direct acting overhead cam eliminates the pushrod and rocker arm so the immediate reaction is that the valve train mass and inertia is reduced. Less valve train mass and inertia is a good thing. But...with a direct acting, hydraulic tappet (like the 93-99 engines) is pretty heavy in itself. And, since the cam lobe acts directly on the tappet there is no rocker arm to add leverage and reduce the effective intertia of part of the valve train. If you look at the picture of the overhead cam roller finger follower you will see that the part of the valve train that moves is actually very light. The roller itself and the rocker arm at the roller moves directly with the cam lobe. The part of the rocker arm past the roller toward the valve tip moves a little more than the cam lobe due to the fact that the lever arm arrangement magnifys the lift. Conversely, the part of the rocker toward the stationary lash adjuster moves less and less. It is stationary at the lash adjuster it pivots on. The actual moving part of the valve train is much lighter than the direct acting system was!! This results in being able to run a more aggressive cam profile with the same valve spring load. Purely due to the lower inertia of the finger follower design and the lever arm advantage and nothing to do with the roller per se. That is one of the ways the 2000 model engines were able to keep the same power rating even with compression ratio reduction and exhaust port constriction (for higher exhaust flow velocities for emissions). A more aggressive lift profile at the valve is the key. Pushrod engines, however, just gain weight when rollers are incorporated, which is counterproductive to a more aggressive cam since more of the valve spring load is used to control the (greater) inertia of the roller valve train. Fortunately, the heavier springs allowed by the roller followers more than make up for this.

The trick would be to get the same valve lift profile for a roller follower 2000 and later Northstar ground onto a flat tappet cam for the 93-99 engines. It would be a "hotter" cam and definitely give more power. Doesn't exist in this universe, though. And if you are going to the trouble to grind one like this then why stop at the 2000 lift profile. Go bigger and more aggressive.

eldorado1
03-25-06, 11:37 PM
The heads will not interchange. You cannot (practically) put the later model heads on earlier engines and you cannot put earlier heads on later model engines...i.e...the flat tappet heads and the roller follower heads will not interchange.


Why? They use the same head gasket. If you're talking about practicality as in, it would be a lot cheaper to stick with the same heads, then yes... But they should bolt on just fine.

chevelle
03-25-06, 11:42 PM
Why? They use the same head gasket. If you're talking about practicality as in, it would be a lot cheaper to stick with the same heads, then yes... But they should bolt on just fine.


They won't. Head bolts are different and different length. For starters, there are no head bolts that will bolt them on. The 93-99 bolts are too short and the 2000 and later head bolts won't work in the earlier engines. The bolts are in the same spot so you would have to have custom bolts/studs made to adapt them.

Secondly, the water crossover casting is different for the 2000 and later engines. You cannot put a 2000 and later water crossover on an earlier engine because the coolant ports on the heads are different and in a different location. IF you put 2000 and later heads on an earlier engine then neither the earlier nor the later water crossover would fit and you would be screwed.

Why would you want to put the later heads on anyway?? They will not perform as well or any better.

eldorado1
03-25-06, 11:48 PM
They won't. Head bolts are different and different length. For starters, there are no head bolts that will bolt them on. The 93-99 bolts are too short and the 2000 and later head bolts won't work in the earlier engines. The bolts are in the same spot so you would have to have custom bolts/studs made to adapt them.

Secondly, the water crossover casting is different for the 2000 and later engines. You cannot put a 2000 and later water crossover on an earlier engine because the coolant ports on the heads are different and in a different location. IF you put 2000 and later heads on an earlier engine then neither the earlier nor the later water crossover would fit and you would be screwed.

Why would you want to put the later heads on anyway?? They will not perform as well or any better.

I assumed you could use time serts for the 2000 engine along with the head bolts for the same.

Roller cams can have faster ramp rates, for longer "effective" duration and still have a decent idle... At least that's what the LS1 guys tell me. Oh, and also you can get billet cams, don't have to worry about regrinds.

chevelle
03-26-06, 12:00 AM
I assumed you could use time serts for the 2000 engine along with the head bolts for the same.

Roller cams can have faster ramp rates, for longer duration and still have a decent idle... At least that's what the LS1 guys tell me. Oh, and also you can get billet cams, don't have to worry about regrinds.

Read my post again.

"Roller cams" do NOT necessarily have faster ramp rates and longer duration.

It all starts with the lift profile as measured at the valve. If you design a lift profile that has faster opening and closing rates and longer duration it will require stonger valve springs to control the system and prevent "no follow". Stronger valve springs could not be used on production engines that need to last for several hundred thousand miles without wearing out the flat tappet cams of yesteryear. The roller cams require (and allow) stronger valve springs without wearing out. The stronger valve springs then allow a more aggressive cam profile. So, the roller cams ALLOW faster ramp rates since they can carry more load but the shape of the lobe on a roller does not inherently have faster lift rates. Many roller cams in production engines had EXACTLY THE SAME lift rates and duration as the flat tappet cams that preceded them at the valve where it matters.

It may be a minor point but the fact is that a roller cam performs no differently than a flat tappet cam if the lift profile at the valve is the same. Only if a more aggressive lift profile is designed into the cam lobe for the roller will it perform better. It is correct to say that a roller cam CAN be designed for more aggressive lift rates and duration but just thinking that that trait is inherent to roller cams is incorrect.

Any cam profile ALWAYS starts with the valve lift profile. The lift profile can be analyzed mathematically. The first derivative (remember calculus...LOL) of the lift profile gives the acceleration of the valve (the rate of change of the valve.) at any given instant. The second derivative of the valve lift profile provides a term called "jerk." Jerk is the rate of change of the accleration. Remember F=MA ?? Force equals mass times acceleration. If you know the mass of the valve train and the acceleration (the first derivative of lift) then you can calculate the force required....the force if provided by the valve spring...to prevent "no follow." So , the available valve spring is the limiting factor in all lift profiles. Nothing to do with flat tappets or rollers. Roller cams just ALLOW stronger valve springs and thus become enablers for the faster ramp rates and longer duration required to improve performance.

As I mentioned, there are cases in production engines where the roller cams actually had SLOWER lift rates than the equivalent flat tappet cams due to the difficulties encountered grinding the roller cam profile...the inverse flank cams.

eldorado1
03-26-06, 12:26 AM
It is correct to say that a roller cam CAN be designed for more aggressive lift rates and duration but just thinking that that trait is inherent to roller cams is incorrect.

exactly. Who would want to stick with the stock 2000 cams anyways? ;)

GreenMachine
03-26-06, 08:03 AM
some great info in this thread.

I have a 98 Deville, and currently it appears the last couple oil changes have used 5w-30. It was said to aid in the cold winters here in Western New York where it can get below zero in the mornings, its a synthetic blend oil by Kendall, also note I haven't had any oil consumption problems now or in the past and the engine has seemed to be running better, smoother idle, smoother accelaration, since the switch to 5w-30 synthetic blend from a standard dino 10w30. The manual says I can use 5w-30.

Now for summer (not summer yet so there will probibly be an oil change before its here) should it have been switched to the 10w30 (blend or full synthetic) or should it have never had 5w-30 in it? I was told at the place where the oil is changed that I can stick with 5w-30 all year round. The Warmest it ever gets here is 80's, rarely 90's, the manuals graph (which somehow blanked my mind when the guy told me about it) shows 5w-30 for under 60*F and 10w-30 for Above 0*F and above 60*F, it also states "-
"FOR BEST FUEL ECONOMY AND COLD STARTING, SELECT THE LOWEST SAE VISCOSITY GRAGE OIL FOR THE EXPECTED TEMPERATURE RANGE." big and bold like that, also says do not use any other oil but 5w-30 or 10w-30.

Sorry to "hijack" the thread somewhat but this through up a red flag for me as I was reading it.