: Can you use 10W-40 in a Northstar



therodman
04-05-05, 03:30 PM
I happen to be looking through the owners manual for my 94 STS and it say's do not use 10W-40 or something other, 5W-20 I think it was. What is the reason for not being able to use 10W-40. I have always used 10W-30 but this was the first time I ever noticed that the manual said do not use 10W-40. Seems there isn't that much off a difference but apparantly so.

I would suspect that maybe either rod or main bearings were getting washed out with the higher viscosity, curious.

Any comments would be appreciated.

Katshot
04-05-05, 03:40 PM
I wouldn't use 10w-40 in ANYTHING. The worst oil you'll find IMO.

Krashed989
04-05-05, 03:42 PM
It says specifically not to use 10w-40? Ohh crap now I have to go look at my owners manual... I have been useing 10w-40 for some time now, I haven't seen any problems with it. In fact I did it to try and slow down an oil pan leak that I have, and it worked.

therodman
04-05-05, 03:49 PM
I'm pretty sure it said do not use 10W-40, I'll check again to make sure. I was kind of surprised to see that, I would have assumed that 10W-40 would have been considered an alternative.

Checking now!!

therodman
04-05-05, 03:53 PM
10W-30 is recommended and then it say's 5W-30 is okay but do not use 10W-40 or 20W-50.

EcSTSatic
04-05-05, 03:58 PM
According to my manual:
"SAE 10W-30 is best for your vehicle. However, you can use SAE 5W-30 if it’s going to be colder than 60F (16C) before your next oil change. When it’s very cold, you should use SAE 5W-30. These numbers on an oil container show its
viscosity, or thickness. Do not use other viscosity oils, such as SAE 20W-50.
If you are in an area where the temperature falls below -20F (-29C) consider using either an SAE 5W-30 synthetic oil or an SAE 0W-30 oil. Both will provide easier cold starting and better protection for your engine at extremely low temperatures."

therodman
04-05-05, 04:01 PM
One reason I started this was because I noticed the new Mobil containers for 10W-30 and 10W-40 look the same with the same color cap. I bought some and the container is silver with a red cap, then I noticed that they have a little stamp in the front in gold for 10W-40 and green for 10W-30, kind of hard to notice. As was buying oil I noticed that they didn't have the blue container, the people in the store said they changed the color to silver/grey, when I picked up a bottle I noticed the 10W-30 and it had a red cap so I grabbed 6 more quarts with the red cap. Later I noticed that I had 2 quarts of 10W-30 and 5 quarts of 10W-40, I thought I had all the same oil because of the red cap. At least I noticed that I had 2 different oil types before I used them or mixed them together.

If you remember, the old blue bottles had a different color cap so you knew the difference, not the new silver bottles, be careful!

therodman
04-05-05, 04:03 PM
EcSTSatic, it doesn't say to not use 10W-40. Everything you mentioned is the same as my manual except mine say's do not use 10W-40 also.

Katshot
04-05-05, 04:12 PM
As I recall the problem is that in order to make a 10w-40 oil, the base crude gets seriously stressed. I remember years ago being told by petroleum engineers with Pennzoil and another guy that worked for a company that did oil analysis for several OEMs in the automotive industry, to stay away from 10w-40. Of course, this would only pertain to mineral oils, not synthetics.

Krashed989
04-05-05, 04:16 PM
I think I should be safe then because I'm in an area where the temperature only rarely falls below even 60degrees F. Right?

WoodShoe
04-05-05, 10:11 PM
Anyone here using Synthetic Oil? I have used it in my previous vehicles with outstanding results imo. But i'm hesitant to use it in this engine because it burns so much oil between oil changes. Im worried it will worsen the issue. ?

maydog
04-05-05, 11:33 PM
Synthetics have a tendency to seep through the bolts holes and such much more than the standard oils. It tends to get consumed / lost faster than standard oils. There is not much to be gained by using them, is what I have heard.

peteski
04-05-05, 11:46 PM
Geez guys....before the rumors get any worse....

You are talking about an owners manaul that is 12 years old....more than a decade ago. A decade ago 10W40 oils were not the same as current 10W40 oils.

A multivis oil is basically the base stock of the lower viscosity with viscosity improvers added to creat the viscosity when hot. The viscosity improvers are long chain polymers that stretch out when hot and improve or increase viscosity and they shrink up into a ball when cold and do not affect the viscosity.

So....a 10W40 oil is about 85 percent 10 weight base stock with 15 percent viscosity improving polymers to give it the (equivalent to) 40 weight rating hot.

A decade or more ago the viscosity improvers used in engine oil were (comparitively speaking) junk and caused heavy ring belt deposits as the polymers were prone to break down in high heat areas.... So....the engine makers encouraged use of oils with as few a viscosity improver percentage as possible. 10W40 has a LOT more viscosity improver than the recommended 10W30 oil. So, it was specifically NOT recommended.

Oils of today are so good that this really doesn't apply anymore. I still don't recommend 10W40 and you don't see it around very much anymore, but, if you have been using a modern, SL rated, 10W40 it is fine. Nothing will be harmed.

The warning not to use 10W40 is more than a decade old and is based on those 10W40 oils of the 70's and 80's and very early 90's that still used the inferior polymers for the viscosity improvers. The oils of today use synthetic viscosity improvers that just do not cause the same sort of problems so I wouldn't be concerned about them at all.

i.e...the warning is old, outdated and doesn't apply anymore. Relax. We need to re-write all those 1994 owners manuals.....LOL

Bbob,
I'm not an oil expert and I've never heard of the 10W40 issues you mention. But I have no reason to doubt you (or others).

But, I owned several cars in the 80s and 10W40 was pretty much the standard oil used in all the cars of that time! When you went to any garage or quick-lube, 10W40 was the "standard" oil available.

So my half-a-dozen cars and millions of other cars were fed a constant diet of 10W40! I'm surprised that they worked at all... :D

This brings up another question: is 20W50 is as bad to use as 10W40? Not on a N*, but just in general?

And what weight is the Rotella/Delvac oil?

Peteski

dkozloski
04-06-05, 01:31 AM
I still remember the statement in the old Detroit Diesel 53 series manual. It said that multi grade oils were a crutch to use to get the engine started in cold temperatures when there was no means of preheat. Otherwise use a good quality straight 30 weight oil such as RPM Delo oil. I also had an '87 Mazda RX-7 turbo that the owners manual said that under no circumstances use synthetic oils because the carbon deposits from it could be hard enough to score the rotor housing. At one time there was a bunch of heavy equipment with ruined engines around here that had been serviced with Union 76 Purple Royal Triton oil. I suppose every oil company has some product that they are still trying to forget about. Phillips paid to overhaul a lot of aircraft engines and Mobil did as well. Skeletons in the closet, still rattling.

Randy_W
04-06-05, 09:19 AM
The stories about 10W40 of the late 70's and 80's are true. They were SE and SF rated oils and were the first of the multivis oils to become popular. Windy, a minor nit pic, I agree with everything else you said. As early as the mid sixties we were selling 10w-30 2:1 over the other viscosities, straight 30w was next. We sold a lot of 40w to trucks and 20w-20 was popular in the winter. Prior to 10w-40 getting popular we sold many thousands of cans of Quaker State Super Blend. Good info, though and something I didn't know about 10w-40.:)

EcSTSatic
04-06-05, 11:19 AM
EcSTSatic, it doesn't say to not use 10W-40. Everything you mentioned is the same as my manual except mine say's do not use 10W-40 also.

Hmmm. That's interesting. I copy-and-pasted from the downloadable manual available on this forum. I searched it and couldn't find anything else regarding multi-vis oil usage. I'll have to look at my hardcopy manual and see what it says.http://cadillacforums.com/forums/images/smilies/hmmm.gif

Ranger
04-06-05, 01:08 PM
I can vouch for what Bbob says re: 10w40 of the 70's & 80's. My father had a 78 Ford and religiosly changed oil every 3000 miles. We used Shell 10w40 at the time. When it had 55K on it, it developed a mis. I finally diagnosed it as a valve. Pulled the engine apart and what I found made me sick. The engine was so sludged up I had to scrape "pudding" out of it. Two lifters were dished and two cam lobes were worn down. That was the last time I ever used 10w40. Glad to hear it's better today but old wounds heal slow. I'll stick with 10w30.

Katshot
04-06-05, 01:44 PM
The only question I have is this, Bbob, in your post you mainly say that the warnings about 10w-40 are old and that nowadays that oil is fine, yet you also say that you don't recommend it. Why don't you recommend it if it's ok nowadays? Just a little confused.
Also, BTW, the comment about 20w-50 should have brought up the fact that it shouldn't be used due to it's poor cold flow characteristics. If you use 20w-50 in many modern engines (especially in the winter), it will increase cold-start engine wear considerably.

therodman
04-06-05, 02:43 PM
bbobynski,

My intention was not to start a rumour thread on the different type oils, as I said earlier, I was surprised to see "do not use 10W-40" in the owners manual. Mobil has changed the container so that I ended up with two different types of oil in my hands, the 10W-30 and 10W-40. I had 5 quarts of the 40 and two of the 30 so I thought, maybe I'll just use the 40 because I had 1 quart of Mobil 10W-40 in the garage from awhile back and that would give me 6 quarts, enough to at least start the car and back it off the ramps.

Before doing this I looked in the manual and like I said, was pretty surpised, I would have thought that at least it would have been an alternate oil to use. Like others have said on this thread, I used 10W-40 years back, not even sure why but recall using it quite a bit.

Once again your insight and knowledge is very much appreciated. With the questions that I have asked about the crossover, water pump, wire bundles and stuck/shorted injectors, you've been spot on and very helpful.

Since I'm here, I may as well ask this question. My car just turned 70k miles, a 94 STS that is just as clean as the day it came off the showroom floor except for the plastic cover for the fan blower motor on the firewall which is starting to crack a bit. With all the threads on head gasket failure, what are the best preventive measures to avoid a future headache. I'm guessing follow the manufacturer guidelines with the proper antifreeze and pellets and that's that, drive it and don't worry.

Thank You in advance!

therodman
04-06-05, 02:49 PM
Ranger,

I just know you were shocked when you opened up that Ford engine and saw the sludge. That's nearly unbelievable, frequent oil changes and all that crud ater 55k, I would have been beside myself and like you said, "sick". Did you ever question Shell or Ford about the "pudding", asking why or how it got there?

therodman
04-06-05, 02:59 PM
bbobynski,

Forget the question about the headgaskets, I found a thread that was titled headgaskets and that answered my quesion.

Thanks anyway!

Ranger
04-07-05, 12:50 PM
Ranger,

I just know you were shocked when you opened up that Ford engine and saw the sludge. That's nearly unbelievable, frequent oil changes and all that crud ater 55k, I would have been beside myself and like you said, "sick". Did you ever question Shell or Ford about the "pudding", asking why or how it got there?
No never did. I knew all I'd get from Shell was a song and dance and it was out of warranty so Ford would probably say bring it in and we'll have a look at it = $$$$. My unprofessional explanation (guess) was that whatever is was that was in the oil to make a 10w change to a 40w was causing the sludge as it obviously took much more to go from 30w to 40w. My suspisions were somwhat confirmed when the big three started telling owners NOT to use 10w40 and if I recall correctly that it would void the warranty. Bbobynski has since confirmed my suspisions. Infact, after that expirience I went back to straight weights til I started having trouble finding them and then reluctantly went to 10w30. By that time oils had started to improve. I wish I had pictures of that engine. You wouldn't believe it.

BeelzeBob
04-07-05, 03:56 PM
The only question I have is this, Bbob, in your post you mainly say that the warnings about 10w-40 are old and that nowadays that oil is fine, yet you also say that you don't recommend it. Why don't you recommend it if it's ok nowadays? Just a little confused.
Also, BTW, the comment about 20w-50 should have brought up the fact that it shouldn't be used due to it's poor cold flow characteristics. If you use 20w-50 in many modern engines (especially in the winter), it will increase cold-start engine wear considerably.



I don't recommend it because I don't like it....LOL LOl Bad memories...???

There is really no need for it, that is why I don't recommend it. It serves no purpose that 10W30 or 5W30 or the Delvac 15W40 doesn't cover. When someone asks what I recommend I try to recommend what I think is best...not a list of what-might-work for them to chose from. 10W40 is not specifically needed nor does it serve a unique purpose so I have never seen a need to recommend it. The 10W40 of today oil is propably strictly because most anything that meets the SL or SM specs is going to be a good oil and much much better than an old SE of SF 10W40 oil which was horrible for ring belt deposits. Just because it is an OK oil does not mean I would recommend it. The fact that I don't specifically recommend against it anymore should really answer your question if you read all the posts in this thread.

BTW...some of the oil makers back in the 70's and 80's knew of the potential issues with the 10W40 SE and SF oils. They wanted to offer a 10W40 product to be competitive in the market place (due to the public's perception that the 10W40 was the best thing around) but did not want to run the risk of the high VI content or using a better VI package that would have put them in a poor price position in the market place....so.....10W40 Texaco Havoline, for example, was "barely" 40 weight. Just barely. Just high enough in viscosity when hot to squeek thru the lower end of the 40 weight specs hot. Just barely enough VI improver to make it the "40" designation. There were some competitors 10W30 oils that were as thick hot as the 10W40 Havoline due to the limited use of the VI package to just barely meet the spec while minimizing the VI content.

Firewireman
06-01-05, 12:25 AM
So someone who really wants to use 20w50 probably could. Just maybe 20w50 in the summer and 10w30 in the winter, right? Is there any benefit at all, specifically in a N* engine, to using the heavier oil when weather permits? Or downside for that matter.

peteski
06-01-05, 12:41 AM
So someone who really wants to use 20w50 probably could. Just maybe 20w50 in the summer and 10w30 in the winter, right? Is there any benefit at all, specifically in a N* engine, to using the heavier oil when weather permits? Or downside for that matter.

Why would somebody insist on using bunch of various grades of oil and ask if there was any benefit in doing so? :confused:

Why not just use what the Owners Manual recommends? Whoever wrote the manual, didn't just randomly pick a specific oil to use. Lots of research went into it.

I just don't get it... :cookoo:

Peteski

Spyder
06-01-05, 12:51 AM
yea...benefits would be a little less mileage and a little more wear...

ktills45
06-01-05, 08:39 AM
Why would somebody insist on using bunch of various grades of oil and ask if there was any benefit in doing so? :confused:

Why not just use what the Owners Manual recommends? Whoever wrote the manual, didn't just randomly pick a specific oil to use. Lots of research went into it.

I just don't get it... :cookoo:

Peteski

Perhaps to understand the rational behind the recommendation better?

Some of us are not as well versed in these subjects as others, and the discussion about the 'how' and 'why' are extremely interesting. That's what makes this board, and Bbob in particular, such a wealth of useful information.

Firewireman
06-02-05, 12:34 AM
See this thread, and you'll understand more why I ask...

http://www.cadillacforums.com/forums/showthread.php?t=41749

peteski
06-02-05, 12:41 AM
I usually don't question recommendations in the Automobile Owner's Manual. If they say 10W30 - I use 10W30.

If my lawnmower manual recommends 30 weight oil - I use it.

Hey, it might be just me... :hmm:

Peteski

davesdeville
06-02-05, 04:15 AM
I don't question the owners manual either but it's nice to hear a rational explanation of why it says what it says. Doesn't technical stuff interest you at all?

lry99eldo
06-03-05, 10:50 PM
From an internet search, and it closely reflects what this old drag racer knows. If you want the best advise, go to the last sentence:

Those numbers refer to the viscosity. In layman's terms, think of viscosity as thickness or, more correctly, how easily a fluid will pour. The syrup you pour over your pancakes is thicker and pours less easily than the coffee you're drinking, so the syrup has a higher viscosity. And as that relates to oil, the viscosity is an indicator of the oil's ability to properly lubricate the engine at a certain temperature. In general terms, the higher the viscosity, the better that oil is suited to work at higher temperatures because as the oil gets hotter it also gets thinner—just as the syrup will—and it will fail to provide sufficient protection if it gets too thin. However, the thicker oil won't lubricate properly at colder temperatures because it's too thick to flow and reach all the vital engine parts.
In the old days oils were what might be called "single viscosity," which meant there would be only one number. For example, on the side of the can (oil came in metal cans then), it might have said simply "30 weight." With single-viscosity oils, people regularly changed oil as the seasons changed, thinner in winter, thicker in summer. To save a little money some people even kept the old oil, and put it back in during the appropriate season. The letter "W" after the number indicated that oil was suitable for winter use.

But a bottle (now we use plastic bottles) that reads something like "10W-30" is indicating a multiple-viscosity oil. In very simple terms, that 10W-30 oil will pour like a 10-weight oil at lower temperatures, yet hang in there like a 30-weight at higher temperatures. Multi-viscosity oils were once known as "all-season," in that they were suitable for all year long—a big thing then. Essentially, single-weight oils are no longer applicable for modern cars, and manufacturers now recommend multi-viscosity oils to provide adequate lubrication in all types of driving.
A few things have changed over the last 20 years or so to significantly change the way we should think about engine oil. The advent of emissions controls means modern engines tend to run hotter, and this places an additional burden on the oil. In addition, in efforts to reduce emissions and improve fuel economy, modern engines are manufactured with much closer tolerances, and operate with tighter clearances between their moving parts. Therefore, what your grandpa told you about oil is no longer applicable.


A typical modern car may require a multi-viscosity oil rated at 5W-20, a number that would have been unthinkable a short time ago. But that relatively thinner oil is designed to work in conjunction with the tight engine clearances and provide adequate lubrication from a cold start-up in the winter in Minnesota to a blistering drive across the desert near Phoenix in the summer. If you use a heavier oil because you think it's "better," you'll not only be wrong, you're quite likely to cause your engine some damage since it won't be properly lubricated during start-up and in cooler weather. Furthermore, if you decide that if a range of 5W-20 is good, then 10W-30 must be better because it's a wider range, you'll also be wrong, since the things done to give that oil the wider range may not necessarily be what your engine needs.

The best oil for your car is what the manufacturer recommends. Use the correct viscosity as outlined in your owner's manual, purchase quality oil from a reputable company, change it regularly, and take good care of your car.

Firewireman
06-06-05, 12:05 AM
That's exactly what I was looking for. Think I'll stick with the 10w30. :thumbsup:

peteski
06-06-05, 01:14 AM
Well and simply explained lry99eldo !

And it still points you to use what the manual recommends...
:thumbsup:

Peteski

JOENH
06-20-05, 08:57 PM
My beater, a 91 Lincoln Continental (The absolute worst car I have ever owned!) has seen nothing but Mobil 1 thru 190,000 miles. The ONLY part of the car that has not required service of any kind has been the motor. My frequency of oil and filter change has been every 6,000 miles (As oils are better today). Five years ago when I purchased my SLS, I stayed with Mobil 1 (10W-30). I currently have 74,500 miles on the speedometer; it "uses" a quart every 1600 miles or so. I don't consider this to be out of the ordinary. The motor runs flawless. I'm 62 and the vehicle has been the best car I have ever owned. As I live in New Hampshire, I believe the synthetic approach helps the motor, particularly in the winter months. I also use it in my garden tractor. From my perspective the benefits of using synthetic oil far outway using (or loosing) a little extra oil. It's expensive but I think its worth it over the long haul (Based on two cars). If you don't put many miles or years on your cars its probably a waste, as regular oils today are a quantum leap from my hot rod days in the 50's and 60's.

highonchai
06-26-05, 03:54 PM
Most dealerships in the south (Florida is where ive seen it) use 10w-40. A Cadillac dealership near St. Pete said that since they started using 10w-40 in all caddy alluminum engines they havent had a single problem.(Im not sure how much truth to that there is) Youll notice a slow crank on cold mornings, but i wouldnt have a problem running 10w40 in my N* at least in the northern summer months.

peteski
06-27-05, 03:17 AM
... but i wouldnt have a problem running 10w40 in my N* at least in the northern summer months.

But the big question is "do you use it yourself"?
:rolleyes:

Peteski

mcowden
06-27-05, 11:26 AM
Most dealerships in the south (Florida is where ive seen it) use 10w-40. A Cadillac dealership near St. Pete said that since they started using 10w-40 in all caddy alluminum engines they havent had a single problem.(Im not sure how much truth to that there is) Youll notice a slow crank on cold mornings, but i wouldnt have a problem running 10w40 in my N* at least in the northern summer months.

Not only have many members here been led astray and been given very bad advice by dealerships, as well as the fact that two self-proclaimed "dealership mechanics" had their egos smashed and brow-beaten by Bbobynski, plus the added bonus that dealerships and mechanics at dealerships don't WANT your car to last forever, I would take that advice, tear it up, burn it, and then blast the ashes into outer space. I don't buy it for one picosecond. The engineers who designed the engine recommend 10W-30 for almost every climate. Unless the climate where you drive your car falls outside of that range, I don't think there is any reason to stray from that advice, especially not based on what some dealership says.

JohnnyO
07-01-05, 11:11 PM
I worked at an Olds-Cadillac dealership in 1983-84. During that time we got a letter from GM saying to discontinue use of 10w-40 in new cars (although it was in the owner's manuals as okay to use) and use 10w-30. bbob is correct, as always :thumbsup:, in that the higher viscosity spread and visosity improvers used to get it were causing problems.

In modern oils, a 10w-40 probably wouldn't hurt except from a gas mileage standpoint. With modern engines and oils, thick is not necessarily good and thin is not necessarily bad. I got lab results back from the 5w-20 at 5000 miles in my wife's Taurus, which calls for that oil, and it looked great.

Just run a high-quality dino oil like Pennzoil or Havoline, or a syn blend or Mobil 1 if it makes you feel better (it does me), in the recommended weight and motor on. :burn: :cheers:

jsjag
08-22-05, 09:05 AM
Hm? Here is the forever on all forums oil discussion. I just picked up a 95 De Vile / NS engine so I can't comment on it. I can comment on my Jaguars. I have an SIII and an XJ40, both run 20/50 in the summer (90 > 105 degrees outside) and one has 148,000 miles on it and runs like a top; the other has 215,000 on it and runs well. No valve problems, no misfire problems. Perhaps the the cam head oil journals (sp) are smaller in the NS engine. Personally I'd worry more about viscosity beakdown in our hot hot summer weathers.