: Premium or Regular Gas?



Unique Distributing
07-27-09, 01:35 AM
So I have been putting regular gas in my car since i took ownership back in march. once in a while i put premium tank of gas into it.

now I have been hearing from people that they ONLY put premium gas in the car. I dont know if this is a prefrence thing or am i supposed to be putting premium gas in the car. I know the ultra high performace cars like ferrari and lambo and mercedes NEED to put this type of gas but I didnt think that a cadillac would need it.

What is the benefits of putting the permium gas and should i be only putting permium gas?


thanks

next2pool
07-27-09, 02:00 AM
I don't know which engine you have, but certainly the V6's should use regular. Premium or higher octane fuel slows the flame front to mitigate pinging so it has the exact same effect as retarding spark. Bottom line is if the engine is not rated for premium (based on your owners manual) you not only waste money but you reduce performance. The knock sensors do not have enough authority to advance past what they are programmed for

Unique Distributing
07-27-09, 02:50 AM
FYI I am running a 4.6 RWD 05 STS

Caroutisine
07-27-09, 07:16 AM
You should run premium all the time with that engine as indicated in the owners manual.

lreddiablo
07-27-09, 05:08 PM
Owners manual says 87 is fine, 91 for best performance

WillySTS
07-27-09, 06:24 PM
Owners manual says 87 is fine, 91 for best performance

Begging the General's pardon, but...wouldn't one buy a V8 equipped vehicle for best performance?:hmm:

rb92gt
07-27-09, 06:42 PM
Regular is fine, won't notice a difference. DO NOT put regular in a V though. Run reg in my 2006 STS V8 with almost 60,000 miles and runs great, in fact runs so hard that I broke a motor mount accelerating... oops, Cadillac fixed it recently under warranty and even replaced my battery for free as it was the original and started to start car a little weak!

MacMuse
07-27-09, 10:41 PM
From the '05 owner's manual which is freely available at gmownercenter.yahoo.com if you have a Yahoo account and tell it about your car. Not sure how many years they have on-line.


If your vehicle has the 4.6L V8 engine, use premium
unleaded gasoline with a posted octane of 91 or higher
for best performance. You may also use middle
grade or regular unleaded gasoline rated at 87 octane
or higher, but your vehicle’s acceleration may be slightly
reduced. If the octane is less than 87, you may get a
heavy knocking noise when you drive. If this occurs, use
a gasoline rated at 87 octane or higher as soon as
possible. Otherwise, you might damage your engine.


My '06 manual has a similar paragraph, which I initially interpreted as 'use 87 all the time'. Guess I owe her a tank or two of the good stuff, although I've never had any knocking.

tlac
07-28-09, 01:39 AM
I use 89 oct. and it seems to be the best balance between the 87 oct. and 93 oct. I also have heard that using high octane gas is overkill can clog up the system over time, and it makes sense. I do notice a difference between 87 and 89, but not as much between 89 and 93. I really wish we had 91 in WI!

Jesda
07-28-09, 02:16 AM
Do what your owners manual tells you to do. Do not try to be clever.

K STS
07-28-09, 09:22 AM
Why are you trying to save 20 cents a gallon in a $50,000 car?

Superjim
07-28-09, 09:41 AM
Why are you trying to save 20 cents a gallon in a $50,000 car?


My thoughts exactly...
The owners manual PLAINLY RECOMMENDS PREMIUM. for the V8's.
Why not just do as the manual says to do?

Makes no sense whatsoever to me. :hmm: :hmm: :hmm:

At 20 cents a gallon...a 15 gallon fillup only costs you 3 bucks more.
On "MY" particular car...I get about 2 mpg better on PREMIUM...so...in that same 15 gallons...I went an extra 30 miles vs using Regular.
At 20MPG..that is 1.5 gallons LESS fuel I burned.
At $2.70 for Premium, it actually cost me less to USE Premium, because I don't use quite so much of it.

But ... each to their own... do what you want... and so will I. :hide:

Texas Jim

TimmyC
07-28-09, 12:29 PM
I run regular in mine and I did the same thing with my 99 without any problems. I don't run it that hard so I don't see any advantage to the higher octane. I've checked the mileage with regular and premium and there is no difference.

stevenriz
07-28-09, 02:42 PM
I run regular in the northstar without issue but thanks to SuperJim's deductive calculations, I may run Premium for a while to compare mileage. I currently avg 18.7mpg driving 120mi/day most of them highway. My trip computer shows between 325 and 333 miles after a fillup. My next fill up will be premium (Mobil), I'll reset the trip computer and let you know the results after a couple of tanks...

K STS
07-28-09, 02:56 PM
You're kidding right? You are going to risk engine problems and worse performance to save 20 cents a gallon?

You bought the wrong car, buddy. You can run 87 octane in newer civics...

next2pool
07-28-09, 03:39 PM
If GM shows that regular is OK (and premium is optional) for certain engines, all of our testing is done on regular--durability, fuel economy, performance. All that happens is the knock sensor dials the timing in till the point of knocking. I won't make any judgement on price vs performance, but there is no way you will hurt the engine since it is validated on regular. Since those engines give the nock sensor enough authority to crank up the spark, you should see a bit of fuel economy gain on premium, so that becomes a judgement call as well. Choices are good :)

MacMuse
07-28-09, 03:41 PM
...
You bought the wrong car, buddy. You can run 87 octane in newer civics...

Careful there K -- you're the one trying to swap out a rear end because you bought the caddy instead of a vette. ;-)

MacMuse
07-28-09, 03:47 PM
If GM shows that regular is OK (and premium is optional) for certain engines... Choices are good :)

And since my Premium rates are usually 30-40 cents per gallon higher and I'm not racing everyone off the line, I may not reach the break even point with improved mileage. But I will give it a couple tankfuls to see how much the mileage improves.

What's the general expectation, does premium help more on long distance highway driving or around town stop/go driving?

C&C
07-28-09, 04:13 PM
And it boils down to the Owner's Manual again; listed under fuel, does it say 'required' or 'recommended' (there's your answer).

K STS
07-28-09, 04:42 PM
Careful there K -- you're the one trying to swap out a rear end because you bought the caddy instead of a vette. ;-)

I've had both corvettes and cobras. The reason I got the STS was because I was thrilled with a full size luxury sedan with ALL the features, and a 0-60 time of 6 seconds. I made the mistake of getting the 2.73 carrier insted of the 3.42. When I fell in love with the car, it was the 1SG package.

next2pool
07-28-09, 05:22 PM
And since my Premium rates are usually 30-40 cents per gallon higher and I'm not racing everyone off the line, I may not reach the break even point with improved mileage. But I will give it a couple tankfuls to see how much the mileage improves.

What's the general expectation, does premium help more on long distance highway driving or around town stop/go driving?

If your looking mainly for mileage improvement, I think you will see a better gain on the highway under light throttle--that way the knock sensor will allow maximum advance. Then of course, you may see nothing at all. Around town and under acceleration, you'll be pulling spark out more frequently and will probably see nothing other than improved performance. Fuel economy is such a difficult thing to judge just with one or two trips because any of the variables can muddle up the results significantly.

aintmisbehavinn
07-28-09, 09:25 PM
I can't tell any difference between 89 and 93. 87 just doesn't cut it...

Platinum06
07-28-09, 10:12 PM
89, This is what i find works best for my 4.6

amgqmp1
07-28-09, 10:16 PM
Where I live 89 is the cheapest gas by a significant margin (subsidized Iowa ethanol). It's not worth 30 cents more a gallon to me, but I don't drive much. I use premium on road trips as a voodoo precaution.

EChas3
07-28-09, 11:06 PM
Gasoline varies a lot by region and refinery. There are over 100 blends. If you notice a difference then you shouldn't use the inferior alternative. GM recommends 'Top Tier' detergent blends, so that's what I use.

Mid-grade and Premium don't provide us any noticeable difference over the RFG 87 Octane we get from our local Tri-Par station. We have no reason to pay more. The manual gives you a choice. If either car performed better or got better mileage, we would opt for higher octane gas or change vendors.

KARL DAHLEN
07-29-09, 09:54 AM
gasoline varies a lot by region and refinery. There are over 100 blends. If you notice a difference then you shouldn't use the inferior alternative. Gm recommends 'top tier' detergent blends, so that's what i use.

Mid-grade and premium don't provide us any noticeable difference over the rfg 87 octane we get from our local tri-par station. We have no reason to pay more. The manual gives you a choice. If either car performed better or got better mileage, we would opt for higher octane gas or change vendors.

ahmen!

lreddiablo
07-29-09, 05:08 PM
Where I live 89 is the cheapest gas by a significant margin (subsidized Iowa ethanol). It's not worth 30 cents more a gallon to me, but I don't drive much. I use premium on road trips as a voodoo precaution.

Ya I remember that driving through, though it was a mistake when I saw 89 was cheapest till I talked to the attendant. Problem is with higher ethanol means significantly lower mileage, lost about 10-15% when I filled up with that 89 blend. Gvt needs to give up on this ethanol thing, inefficent source of fuel!

cooncat
07-29-09, 05:31 PM
I have been putting regular into my STS northstar and it runs just fine. There are reports in the news lately stating that unless your car is an extremely performance car, putting premium is a waste of money. By the way, I did put in premium at the beginning and noticed no difference in performance or mileage.

Caroutisine
07-29-09, 09:04 PM
And I'm sure N* engine will run just fine on non-synthetic oil as well :)

I guess I've always done what's recommended in the manual.

Superjim
07-29-09, 10:35 PM
^^^^^^^ What he said. :cool2:

Onalaska
07-29-09, 11:47 PM
Always put regular in mine for 47,000 miles now, no knocking, good performance and gas milage. I guess if I drove it hard every day I would consider higher octane, but can't see any reason to waste money regardless of what I paid for the car. Not really a good comparison to using synthetic motor oil. Mobil 1 is the only oil recommended.

D&Ds_STS
07-30-09, 06:37 PM
Excellent posts and info. I am going to try the 89 octane. Will have to rely on my wife's superb hearing and lead right foot as my spark knock detectors. By the time I hear it, we are at the valve rattling, gravel in a can noise stage.

EChas3
07-31-09, 02:04 PM
Excellent posts and info. I am going to try the 89 octane. Will have to rely on my wife's superb hearing and lead right foot as my spark knock detectors. By the time I hear it, we are at the valve rattling, gravel in a can noise stage.

I've yet to hear that. I hope I never do.:crying2:

mikey1026
08-02-09, 12:56 PM
i put premium in my sts without anyone telling me to, because i love her lol

next2pool
08-02-09, 08:21 PM
i put premium in my sts without anyone telling me to, because i love her lol

Well now, that's by far the best reason I've heard yet :) Considering my experience with love, Maybe I should try it as well!!

stevenriz
08-05-09, 08:35 AM
I'm on my third tank of premium with an avg of 1.1mpg better. My travels are 110+ miles per day of both highway and rural route driving. It's too early to think but I don't know that it's worth the extra $5 per tankfull seeing I am filling up twice per week or so. I might try the middle grade to see if mpg change...

Unique Distributing
08-05-09, 10:48 AM
5$ per tank thats it! for me to switch to premium it would cost me 12-13$ per tank more. gas right now in ontario canada is 96.9 cents a litre and premium is 117.2 a 20 cent diff! if it was only costing me 5$ a tank i would be doing it forsure.

KARL DAHLEN
08-05-09, 11:05 AM
Maybe your getting slightly better mileage because it is recommended for that engine. In any case, do the math. It is costing you more $ per mile to run premium assuming a $.20/gal difference.

EChas3
08-05-09, 11:30 AM
17.5 X .20 = $3.50 ~ 7.7% higher cost @ 2.599 for Regular (3.5/45.5)
Assuming 27 MPG on Regular ~ 4% better mileage (1.1/27)

From a cost perspective, it's not worth it. You would need a 2 MPG improvement if that is your only concern. You can weight the other factors as you choose.

IMHO, you may be able to find a brand/grade of gas that provides the performance/mileage at lower cost. But if premium makes you happy, go for it!

Have fun!

bbshriver
08-05-09, 01:03 PM
I've only put premium in mine. I haven't looked in the owners manual but I believe (I'll check) that mine has a sticker on the gas cap to use 91 octane or higher.

Besides that, with things getting tight, I figure I'll go to the high end of their recommendations for warranty issues. While using 87 may be adequate, if I had any issues with the engine they could pull that. Even though their manual says otherwise it could at least cause some hassle? Anyway, for the minimal cost difference I'll stick with what the sticker on my gas cap says

K STS
08-06-09, 11:37 AM
Same here... if you want a vehicle that runs 87, go buy a kia. Dont buy a $60,000 STS and then try to save 20 cents on premium fuel... :dance7:

C&C
08-06-09, 12:45 PM
If you've got a V-6, regular is all you need. Some of the early N*'s required premium, some of the later models recommended premium. Premium is a misnomer, it just has higher octane; if you don't need that octane you don't need premium (if you do, you do). The cost of the vehicle has not much at all to do with the equation; using that as a arguing point is 'pretzel logic'.

KARL DAHLEN
08-06-09, 02:32 PM
If you've got a V-6, regular is all you need. Some of the early N*'s required premium, some of the later models recommended premium. Premium is a misnomer, it just has higher octane; if you don't need that octane you don't need premium (if you do, you do). The cost of the vehicle has not much at all to do with the equation; using that as a arguing point is 'pretzel logic'.

RIGHT ON brother!

K STS
08-06-09, 03:19 PM
Just like you said - "if you don't need that octane you don't need premium (if you do, you do)"

The manual for my V8 STS says premium is recommended. If i recall correctly, it says you can use 87 or 89 if you need to. So why would you buy a premium luxury car, and not use what Cadillac recommends?

WillySTS
08-06-09, 09:07 PM
Just like you said - "if you don't need that octane you don't need premium (if you do, you do)"

The manual for my V8 STS says premium is recommended. If i recall correctly, it says you can use 87 or 89 if you need to. So why would you buy a premium luxury car, and not use what Cadillac recommends?
:rockon::werd:
I'm impressed K...that's the most sensable thing I've seen you post! I think you're growing up!:thumbsup:

Platinum06
08-08-09, 04:20 AM
And I thought with 89 she ran strong....? 92 it is then.

EChas3
08-08-09, 08:47 PM
There is more to gas than octane. A cheap gas leaves deposits in the throttle body. These cars have a tendancy to have problems there, too.

If the car isn't pinging and performs well on a 'top tier' lower octane gas, anything more expensive is a waste.

Maximln
08-09-09, 09:09 PM
Regular is fine, won't notice a difference. DO NOT put regular in a V though. Run reg in my 2006 STS V8 with almost 60,000 miles and runs great, in fact runs so hard that I broke a motor mount accelerating... oops, Cadillac fixed it recently under warranty and even replaced my battery for free as it was the original and started to start car a little weak!

The dealer replaced your battery with 60,000 miles on it? What warranty do you have?

Thanks,

Max

ramon222003
08-12-09, 07:03 PM
the manual for my 05 STS V8 says 91 octane or higher. basically premium. so thats what i put in the tank every time. you may be fine with regular on the V6.

turnne
08-12-09, 08:30 PM
Same here... if you want a vehicle that runs 87, go buy a kia. Dont buy a $60,000 STS and then try to save 20 cents on premium fuel... :dance7:


a 60K STS that he probably bought for 20K
I really doubt there is any need to keep refering to that sticker for two reasons
1. You do realize that these cars sell for no where near those sticker prices?
2. You do realize that after 3-4 years the cars is worth about 1/3 of that sticker

that needs to be kept in perspective

if you save 20 cents a gallon ...for some one that buys a 20K car...that has to make a difference

Warren

Unique Distributing
08-12-09, 11:44 PM
i put sonoco 94 octane in the last 2 fillups and dont notice any diff. I think ill stick to just filling up with 94 octane once a month or so.

It cost me 18$ MORE for my fillup using the 94 then the 87 octane.

MacMuse
08-13-09, 08:44 AM
My first full tank of Premium (Shell 93 Octane) is complete, and my mileage DROPPED over 1 MPG. I went for a second tank and will try to get a little more highway driving. It felt like cautious city driving actually performed worse than before (slower response to pedal, Instant MPG never as good as previous 89 Octane tank).

Does the computer car more time to readjust to the different mix? Does it need some WOT to wake it up?

next2pool
08-13-09, 12:08 PM
My first full tank of Premium (Shell 93 Octane) is complete, and my mileage DROPPED over 1 MPG. I went for a second tank and will try to get a little more highway driving. It felt like cautious city driving actually performed worse than before (slower response to pedal, Instant MPG never as good as previous 89 Octane tank).

Does the computer car more time to readjust to the different mix? Does it need some WOT to wake it up?

The computer does learn over time but not for this issue--the knock sensor adjusts the timing real time. Is your car a N* or a V6? The V6 won't respond much to premium. Also, fuel economy can be affected by so many variables that 1 tank full may not be enough to get a true reading.

MacMuse
08-13-09, 01:12 PM
N* 4.6L

Construction picked up on my highway route option to work last week, so I didn't get as much 60mph cruise time on this first premium tank as I needed for an equal test against the previous tank.

But I am having fun with Gas Cubby, a little iPhone app for tracking basic gas & service costs. With careful usage you get nice charts on cost per mile, etc.

On a side note, anyone using DevToaster's REV software for iPhone and any of the available hardware/wi-fi based OBD cables? The cable connects to the OBD port and broadcasts over wi-fi to the iPhone software. It will show error codes and most of the performance data available through OBD. I've played with the REV software, but it's really useless without the OBD cable.