You know, what I find interesting, and a bit confusing, is the Owners Manual statement of recommending "premium" fuel for the 2.4. My question is, "what exactly is premium fuel?".

I've been to many locations throughout the U.S. and noticed "premium" fuels with stated octane levels of 90-94. So, as GM states, why is a stated premium fuel of 90 better than a mid grade, 89, found elsewhere.

I actually believe GM is just covering all their bases (AZZes) by stating "premium". It's a bit nebulous.


In my experience, I have found a mid grade, 88-89, to be the best trade off....performance vs. cost vs. mileage.

 

You will find the octane rating of "Premium" fuel can vary due to altitude and prevailing climate conditions in various markets. Go from buying gas in New Orleans to buying it in Denver for an example of octane ratings varying due to geography and climate.

 

On my old 2006 LS 2.2L, I ran 87 octane. Almost got two weeks of fuel. Once a year I would put in 93 octane to clean her out.

 

From my manual.....

 

You are absolutely correct, Greybeard. I stand corrected.

 

Not required, only recommended. I call it "premium optional". The HP and torque rating for the 2.4 is when using premium. Any lower octane and those ratings go down. As they say, YMMV. Some people see no difference, some do. I see a slight increase in mileage, enough that at $4 a gal, I save about $200 a year. I also see a nice performance increase at freeway speeds. So for me its worth while. but I always tell people to test 2 or 3 tank fulls and decide for themselves.

93 will do nothing to "clean it out". The computer simply sees it as a change in conditions and adjusts accordingly. Use a good fuel injector cleaner every 6 months no matter what octane gas you use.

 

VVT motors use a whole different set of parameters to measure fuel requirements. PRE-VVT cars you essentially had a stock tune that is generally FAT and adding some basic mods will not only gain power but lean out the A/F to more reasonable level. Beyond basic bolt ons would require some adjustment. Also when running lets say 87 oct. you had high oct and low oct fuel tables so unless a tuner made them equal then you were fine.

At least on some the Camaros with VVT, you toss a CAI (cold air intake) and there is a good chance you get some driveability issues. I have not done tons of research but this leads me to understand that they can be cranky and having a little better resistance to knock is probably required.

 

I've been running mostly 87 octane in my 06 HHR for 85,000 miles. I have tried using 93 octane for 2000 miles and saw no improvement in mileage, however it (seat of the pants) felt more peppy while running 93. I'm not into having a daily driver as a performance car. BTW the last four tanks of 87 octane, I was getting 34+ mpg on highway road trip.