what type of fuel?

[tonytun]

but isnt premium gas recomend it and better? i really dont care about the money i guess is just like a 4 dollar difference everysingle time i full it......sry robert but i being thinking and i dont know what to do now lol i mean i just want whatever is best for my car....... now if premium gas is not good for my car then i guess i'll switch to 87 what do u guys think???

[mrplease]

tony, if the extra money doesn't concern you then put in the high octane! i have always used the high octane and it works fine for me. and your right, its not that much of a difference in cost...

[RobertCTS]

Yep Tony, use what you want. The higher octane gasoline has anti knock additives. since you don't have knock why would you want to use it? A placebo for Tony??

[bigblockcadillac]

Originally Posted by RobertCTS

Yep Tony, use what you want. The higher octane gasoline has anti knock additives. since you don't have knock why would you want to use it? A placebo for Tony??

Yeah, just wait until you have a problem, never try to prevent problems

[RobertCTS]

Originally Posted by bigblockcadillac

Yeah, just wait until you have a problem, never try to prevent problems

What problems?? It's the fuel recommended by the GM Engineers who designed the 3.6VVT.

[kbevere]

Iv been told by the dealer when i gotten the car to use 87 i dont need anything higher!

[RScar627]

I bought my '03 with approx 25,000 miles on it and have put over 30,000 miles on it since. I tried both when I first got the car but didn't notice any appreciable difference so I have stuck with regular. Also, the dealer I bought from told me regular was okay to use. I believe the manual says to use premium for best performance but I really don't push my CTS to the limits.

[Chief_AT]

The higher octanes don't have more energy - just a different formulation to prevent knock. This is done by raising the 'vapor point' of the fuel - the pressure/temperature point at which fuel will self-ignite, which is what knocking is. Higher octanes will not work in very low compression engines (like lawn mowers [7 to 1]), because the low compression doesn't heat that fuel sufficiently for the spark plug to create combustion. Higher compression engines, like our 3.6, do, so higher octane is only needed if knocking is noticed with a lower grade.

[Paco.]

does higher octane fuel burn cleaner than lower?

[RobertCTS]

Originally Posted by Paco.

does higher octane fuel burn cleaner than lower?

No it doesn't unfortunately

[Aurora5000]

The Bottom Line Most cars don't need premium, but a few do -- and not necessarily the ones you'd expect. And premium's not likely to "clean" your engine, either.

While many people claim that their car runs better on premium, this costly fuel is really only needed in a few circumstances. However, when it is needed, it must be used to spare your engine from costly damage. On the other hand, if you burn premium when your car doesn’t need it, the damage won’t be to your engine but only to your pocketbook.

It’s All In The Numbers

The AKI (anti-knock index -- also known as "octane rating") of the fuel is an average of two different methods of computing the fuel's ability to resist engine knock. Regular unleaded gas in the U.S. has an anti-knock index of 87, while mid-grade is usually 89, and premium typically is 91 - 93. The higher the number, the more anti-knock protection the fuel offers.

Engine knock occurs when the fuel in the cylinder ignites by itself before the spark plug ignites it. The technical name for this condition is "pre-ignition." It sounds like marbles rattling around in a can, and it generally gets worse the harder you press on the accelerator pedal.

Knocking can indeed damage an engine because what is in effect happening is the "explosion" of the fuel/air mixture is trying to push the piston downward in the cylinder before it's gotten to the top of its stroke and is free to move downward. The engine is actually working against itself to a degree, and there is a lot of mechanical stress placed on certain engine parts, such as the pistons. In extreme cases, knocking can burn holes in the pistons and create other forms of engine damage.

Oil companies sell higher AKI fuels (also known as premium) to address this problem. A fuel with a higher AKI actually burns more SLOWLY than fuel with a lower AKI. This is because the fuel is less volatile and requires more heat input before it begins to ignite.

(For this same reason, high AKI fuels will actually make your car HARDER to start on a very cold day. In extreme cold -- below 0 degrees F -- you want a more volatile fuel which ignites easily so you can get the engine going without extensive cranking. So if extreme cold is expected, buy 87 AKI gas unless your owner’s manual advises against it.)

Who Needs Premium?

Basically, all premium fuel does is resist knock. So the short answer to the above question of “Who Needs Premium?” is simply any vehicle whose engine knocks without it. Consider these guidelines as you decide whether you really need premium or are in the majority who do not:

1. If your vehicle makes the above-described knocking sound when you accelerate, try the next higher grade when you refuel, and then see if the knocking goes away. If it does, stick with that grade. If not, bump it up another grade the next time you get gas. Generally speaking, high mileage vehicles with a lot of carbon deposits in the engine are likely candidates for needing premium or mid-grade gas, since these deposits reduce the volume of the engine's combustion chamber and make knocking more likely. In addition, the carbon deposits themselves get hot and may act to ignite the fuel if lower AKI fuel is used. High mileage engines do not always have carbon deposits; those that have been driven mainly in town and done a lot of idling are most likely to be “carboned up.” My Ford F-150 has 210,000 miles on it and does not knock on 87 AKI regular unleaded, so that’s what I use.

2. If your owner's manual calls for higher AKI fuel, use what the Book says. Usually this will be specified by manufacturers of high compression, high performance engines. If lower AKI fuel were used in these engines, performance would suffer because the engine's computer system would have to retard the ignition timing (reducing horsepower and fuel economy) to keep the engine from knocking.

But I Want to Keep My Engine Clean!

The higher AKI of premium gasoline does not in itself make it any cleaner than regular gas. Oil companies, however, like to advertise that their premium fuels are ‘specially formulated” to clean fuel injectors, restore lost power, and, hey, maybe even improve your sex life. But the truth of the matter is that any “cleaners” that could be added to gasoline itself are probably not going to be present in sufficient quantities to do much good.

A better strategy to keep your fuel injectors clean is to buy your gas from reputable stations that have a relatively brisk business. In this way the gasoline is liable to be freer of water and other contaminants. It’s also not a bad idea to avoid buying gas from stations while their tanks are being filled by a big tanker truck. It’s possible that the filling process could stir up gunk that’s settled to the bottom of the station’s storage tanks and make it more likely that debris could wind up in your own tank. (Gas stations have filters that are supposed to prevent this, so this is a minor point for those who want to be extra careful; it’s not a really big deal.)

[Mak-B]

Originally Posted by djnas

hey guys...

i have the 03 CTS and from my intepretation of the manual it says u can use 87 Octane, but Preimum is obviously recommended, I have put on about 8000KMs on the car since ive had it, I live in Toronto and i have used 87 octane for the majority of my driving.. I have to say it works fine..

However on my last fillup i used 91 octane and the acceleration at lower speeds is certainly better and noticable,

also i noticed once when i started my car it vibrated a bit (it was near empty on 87 octane gas) and when i put premium i didnt notice it. It could just be a one time thing cuz i never noticed a slight vibration before, even when using87 octane fuel.

My take is that 87 octane is ok for the 03 CTS if u dont push ur CTS hard and are an average driver, but if u want better performance premium is definately the way to go...

any1 else here use 87 in thier 03 CTS? ive only driven 8000KMs so maybe thats why i didnt notice a difference yet, any1 else here have more experience with this?

Crap! I've been using 87 on my used 03 CTS for over 4 months and I haven't noticed any 'issues' nor any hesitation in accleration. I was under the impression that CTS never required premium, so I never bothered. I think its recommended but will work fine with regular.

[bburt]

Hi folks. I've also noticed some difference in mileage and performance between 91 and 87. I drive from below sea level-really!- to over five thousand feet and from coast to desert regularly. Temperature and humidity can make a difference. In the cooler, moister coastal air, 87 is fine. On the road, if I'm in a hurry, I'll top off with 91. Being in California, we have higher levels of ethanol in our blend, so that also has some effect. For normal, around town, I use 87 and have no issue. If I need higher performance, I go with the higher grade. The higher grade boosts mileage nearly enough, it seems, to offset the higher cost. That a couple of miles per gallon difference. I can state pretty much to a certainty that any gasoline from a reputable source will have the same value in terms of keeping the system in proper condition. All will eventually need to have the throttle body cleaned, and other maintenance items seen to. That's my experience, anyway. Best to all.