: Premium gas?



dmokry
03-04-09, 12:52 AM
Do you really need to burn premium fuel in the STS V-8 engine? My 99 STS ran fine on regular. The DTS says regular what is the difference?

Thanks.......moke:bigroll:

SwissSTS
03-04-09, 03:28 AM
The Northstar engine in the STS has a higher compression ration than the version in the front wheel driven DTS or in the older generation STS.
Premium fuel is recommended to get full power but as the PCM has also a timing table for low octane fuel, it can handle regular.
Only the supercharged engine requires premium fuel.

mbnv992
03-04-09, 07:56 AM
The owners manual recommends premium fuel for the 2005-up STS's. I always use premium on my V8. A few times I did put regular 87 octane in, and I noticed severe engine shuddering upon acceleration, getting up to speed took longer, and I also experienced some spark plug knocking as well. So, I would definitely just use premium over any other fuel. (The manual recommends at least 91 Octane or higher for this car).

justgreat
03-04-09, 09:00 AM
the n/s engines in the fwd sevilles/sts were prone to combustion deposits in the combustion chamber. engines that were not driven hard and did not see alot of high rpm use were prone to the deposits, which led to poor driveability and reduced fuel mileage. i think by 2000 the engine had been redesigned to better burn the high octane fuels....and it had nothing to do with compression ratios; it was done by different valve timing and cam grinds.

one last point: all fuel grades leave the refinery as 87 grade fuel. additives are then used in varying amounts to meet the octane and anti-knock requirments for the other grades. it was these additives that caused the deposits to form in the cc when the engine wasn't driven hard.


jackg
06 sts6

EChas3
03-04-09, 11:18 AM
The difference is negligable in my 2006 & wife's 2007 using most of the gas available in this area. There is one convenience store chain that I avoid. With that exception, we use the least expensive 87 Octane we can find. We go to many different suppliers.

Mbnv992 - I'd say you're doing the right thing. There are so many gas formulations for different areas of the country and seasons (I've heard over 100) that it's truely a matter of "Your results may be different."

I know my area (Southeast Wisconsin) uses a gas formulation that is unique and only made in a few refineries. A year ago when prices were so high, ours were nearly as high as San Francisco's. There was talk about relaxing the restrictions on gas formulations to ease the pressure. When certain refineries close for whatever reason, our prices spike.

I can't believe that emission limits can't be met with fewer specific formulations. Cars today are clean-burning on almost any of these many varieties. We get better mileage when using gas from outside our 5-county EPA district.

I have a friend who was a Petro-Engineer (or whatever) that worked for Exxon years ago. He said that 'Put a tiger in your tank' was not just advertising. He said they used an octane-boost additive that built up in cylinders and if someone changed to a different brand or lower octane, they would notice the difference. Over time, any advantage of the additive would be lost. Sounds like an Urban Legend but his degree was from Georgia Tech (a good engineering school).

jdillane
03-04-09, 01:40 PM
my v8 2006 recommended 89 octane. always went with that and no problems. My 99 called for premium and I always obliged. I believe the 2000 model called for regular.

MARKVIII
03-04-09, 03:58 PM
my v8 '05 has been drinking 87 octane for 3 years with no knocks, pings or loss of power..

turnerbend
03-04-09, 06:48 PM
It have been proven that premium fuel in any car is a waste of money unless you drag racing .

WillySTS
03-04-09, 07:51 PM
It have been proven that premium fuel in any car is a waste of money unless you drag racing .

No, it hasn't. It has only been proven that the car will run on it, which it will. I have proven the exact opposite with a CTS-V that a customer swore the car ran great on regular gas. I called him up and had him come down for a test drive. I drove the car somewhat normally but when I would accelerate after a shift you could always hear a rattle noise for a few seconds. I asked him did he hear that, he says "hear what?" I did it again and said, "you don't hear that?", he says "oh, that!...thats just a rattle I hear sometimes." I said I'm going to do something for you. So, we filled up the car with premium and drove some more...I could not get the car to make that noise(detonation) with pemium gas.

A question for you...have you ever seen the inside of an engine after prolonged detonation? It is very ugly and can go unoticed for quite some time to deaf ears to that kind of thing.

One other thing, don't ever try that in a STS-V, you may not be so lucky.:thepan:

justgreat
03-04-09, 08:18 PM
engines are designed and engineered to run on a particular grade of fuel. for absolute best throttle response and power ouput numbers, premium would be engineered for the engine. when the infiniti 3.7 v6 makes 333 hp it NEEDS premium. i willsay that in most cases, if an engine was designed for regular versus premium, the difference in performance in the real world would be hard to detect, imo.


jackg
06 sts6

hazcaddy
03-04-09, 08:23 PM
Willy:

I notice you're in Lotusland where they have designer gas. The rest of us may not have quite as finicky a range of fuels available to us.

This thread is interesting in that it takes me back about 10 or 11 months, when here in Southern Ontario we actually ran out of gas. There was a perfect storm of low supplies in general, a huge refinery fire, and a railroad strike which led to people having to cruise around looking for a gas station that wasn't displaying "00.0" on their signs. That really makes you sit up.

It lasted almost a month and when gas WAS available, it would only be Regular. All the Lexus, Mercedes, etc. drivers whose manuals mandated Premium were required to pump Regular: there weren't any broken-down high-end cars by the side of the road so I guess the Regular didn't kill their engines...

Caddy Man
03-04-09, 09:45 PM
I accidentally filled up my 2005 STS V8 with unleaded a few weeks ago. There was a very noticeable difference in performance and acceleration. When I would give it 90% throttle and then ease off the throttle, the car would jerk as if the engine completely cut off. The car drove fine without any noise or sounds, but the performance decrease could be felt. And no, this was not a figment of my imagination. A friend of mine who is familiar with my car also noticed.

The manual recommends premium and that is what I am going to use.

turnerbend
03-05-09, 12:12 AM
No, it hasn't. It has only been proven that the car will run on it, which it will. I have proven the exact opposite with a CTS-V that a customer swore the car ran great on regular gas. I called him up and had him come down for a test drive. I drove the car somewhat normally but when I would accelerate after a shift you could always hear a rattle noise for a few seconds. I asked him did he hear that, he says "hear what?" I did it again and said, "you don't hear that?", he says "oh, that!...thats just a rattle I hear sometimes." I said I'm going to do something for you. So, we filled up the car with premium and drove some more...I could not get the car to make that noise(detonation) with pemium gas.

A question for you...have you ever seen the inside of an engine after prolonged detonation? It is very ugly and can go unoticed for quite some time to deaf ears to that kind of thing.

One other thing, don't ever try that in a STS-V, you may not be so lucky.:thepan:

A few months back when gas supply was low, everybody burn whatever they could get. If you drive normal, you can use regular. I have used regular often in my 96 Deville North* (120,000 miles) no problems.

Aurora5000
03-05-09, 09:12 AM
Use 87 Octane for my V-8. Works for me. Also for the CTS>

C&C
03-05-09, 10:09 AM
Your owners manual is the reference you need to seek. It will say regular, or reccomend premium or premium. It even explains why.

WillySTS
03-05-09, 11:14 AM
As I said... IT WILL RUN ON IT...,even the owners manual says so,but, should you use it all the time? Not in a '05 and up N* of any sort. Heck, even my pickup(2003 Silverado 5.3) knows the difference, but I should point out its PCM has been tuned for 89-93 octane and there is a noticeable difference when not using premium and will not tolerate 87 anymore...so, there IS a difference between premium and regular.

justgreat
03-05-09, 07:30 PM
the straight six in the bmw vehicles requires premium grade fuel....it doesn't recommend premium it requires it. that tells me that the software is not the type to adjust the ignition parameters to compensate for a lower grade fuel. the 2010 mustang gt has the software to alter the parameters in line with what grade is used.



jackg
06 sts6

Caroutisine
03-06-09, 02:09 PM
I use premium as recommended in the owners manual. It simply does not cost that much more than regular unleaded. I knew the recommended fuel for the car was premium when I bought it, so there's no reason not to use it. Why would I not want the car to perform at its best for a few extra cents?

suumz
03-08-09, 08:57 AM
I use premium as recommended in the owners manual. It simply does not cost that much more than regular unleaded. I knew the recommended fuel for the car was premium when I bought it, so there's no reason not to use it. Why would I not want the car to perform at its best for a few extra cents?

Agreed. If you can afford to own one of these cars, you should be able/willing to pay for the recommended fuel. What is it? Like $4 difference at the most on a fill up?

turnerbend
03-08-09, 10:00 AM
Agreed. If you can afford to own one of these cars, you should be able/willing to pay for the recommended fuel. What is it? Like $4 difference at the most on a fill up?

I don't think its a matter of what a person can afford. You use the fuel you want knowing the consequences of your actions. If it hurt the performance, live with it. If it cause a failure then live with that. As far as the affordability, there's a lot of cars in this price range. Everybody owns a Cadillac.

hazcaddy
03-08-09, 01:22 PM
As I have a V6, and no access to a V8's manual, I don't know whether it says Premium is "Recommended" or "Required". There is a big difference: Recommended = Premium is good, but it'll run on Regular; Required = Premium good, everything else bad.

WillySTS
03-09-09, 06:59 PM
This is what the owners manuals say...wording is only slightly different from model to model...

STS-V, XLR-V and CTS-V it says "required, damage caused by the fuel lower than 91 octane is NOT covered under warranty".

All other Cadillacs,2005 and new(except CTS-V), 2004 XLR that recommend premuim fuel...recommended..."you get maximum performance using fuel of at least 91 octane, however, regular fuel can be used with reduced performance". It also says..."if you hear a knocking,pinging sound while driving up hills or on brisk acelleration, use gasoline with a higher octane".

Jesda
03-10-09, 07:27 AM
Do what the manual suggests.
Do what the manual suggests.
Do what the manual suggests.
Do what the manual suggests.
Do what the manual suggests.

aintmisbehavinn
03-10-09, 09:17 AM
My Goat turned a 13.59 at Atlanta Dragway with 91 Octane. I put 2 gallons of 105, it turned a 12.66. Higher octane is better for your timing tables.

I put 87 in my STS during the fuel crunch, it drank all of it. Put premium back in it actually got better gas mileage. For a few dollars more per tank, she will get the best. The hell with cheap gas.:alchi:

EChas3
03-10-09, 12:35 PM
The 2006-2007 Northstar handles marginal fuel much better than my previous cars. I see little difference in mileage or performance.

I had a Lincoln that would get an extra 2 MPG (~10%) on 91 Octane. When gas was over $2, it was worth it.

My old '93 Roadmaster would ping on one brand of discount gas but would usually run fine on 87 Octane. 25 MPG @ 75MPH was normal. My wife's 2007 STS RWD N* does the same at 80. :thumbsup: