As a 6th gen owner, I'm sure some of you have noticed the difference in car's performance and increase/decrease in mpg. I have no experience with 3.5s so I don't know which product to choose when going for "premium gas" I'm not so fussy about the gas prices... it's only a few dollars more.

 

I only go with the Shell V-Power --- what a difference with that

 

we only have up to 93 here and thats all I use, never used anything else.. MOBIL

 

I use Shell V Power 93 as well...mainly because i have a credit card that has good rebates for purchasing Shell gas.

 

shell 93 only

 

To my knowledge, Sunoco is the only one selling a 94 octane gasoline, and only in certain locations -- they don't have it in South Carolina, for example.

The owner's manual says use 91 octane premium for maximum performance. To me that says the engine was designed to provide maximum performance for that octane gasoline. If this is true (and I believe it is) then any additional octane (without making changes in the engine) will NOT give you any better preformance.

There are exceptions to this. For example if you have extensive engine deposits, they can increase the engine's need for higher octane. Turbocharging the engine obviously will increase the octane requirement. Otherwise, save money and buy 91 octane.

If you don't need maximum performance, you can save even more money as the VQ engine runs just fine on 87 octane regular. Don't burn regular if you want the maximum from the engine (racing, dino test, etc). But if you don't get your foot into it very much, save more and burn regular.

 

For the 6th gen owners:

If you have used lower octane fuels, have you noticed a strong gas smell in the mornings till the car is warmed up?

 

No. But I'm probably not a good test of this question. I vary rarely use premium. But I don't notice any smell with a cold engine from the exhaust, even burning regular.

 

I was afraid of that. I've had this '04 for about 3 weeks and when we had a turn in the weather (cooler), I started smelling gas when the car was first started. Once the car had been run for 10-15 min, the smell would go away till the next morning. The dealer is looking at it now and can't find the source.

I know there is a TSB for Air/fuel sensor heater/ closed loop. Don't know if that would have anything to do with my problem or not.