87 or 93?
 

What type of gas works best in your engines?

Do a search.....many threads and opinions on this topic.

Just last week I ran a 2 day test of 93. I generally drive 300 - 400 miles a day in mixed use and keep computerized records. The result was: MPG 87 = 24.7 93 = 25.9; Cost Per Mile 87 =$ .11 93 =$ .14. In other words I got a little better MPG, but worse CPM. Not a long term experiment, because I could not afford to spend an extra $2 to $3 a day for long. BTW, the price of gas was stable that week, so CPM comparison is fair and I did not have to relearn "statistical analysis". 2008 HHR LT 2.2L auto with 192,000 miles in mixed use with A/C running.

Since you have a 2.2 it will run just fine on 87 since its tuned for that, but the odd tank of Premium as a treat never hurts. I've never noticed any appreciable difference in mileage between running 93 in my 2.2's and just sticking with 87 octane. That being said, the occasional tank of something else is beneficial because of the different levels of detergents and other additives in higher grades of fuel. A tank of "rocket fuel" can help clean out some deposits that the normal diet might not get.

Because of the general unavailability of E-85 in this part of Carolina, I can't give any input on that, but its an option since you have a Flex Fuel HHR.

Have you found any appreciable difference using 93 octane in your 2.4? Only on extremely hot, humid carolina power draining days have I found 93 to make a difference, and that may be my imagination. I have done multiple tanks of 93,89,87 and don't find any difference in gas mileage. I do find that using AC reduces gas mileage by around 2mpg, but that won't keep me from being cool. HHR has a strong AC. Sorry guys, I forgot this was the 2.2 forum.

With a 2.2L you probably won't see any difference. I have seen a difference with the 2.4L though..... Enough to run it all the time.

I have an 06 with the 2.4L auto and never found any better mpg using 93 vs 87 octane. I've been running 87 most of the time. I did do a 2000 mile experiment using 93 and saw the same range of mpg 30 +/-2 mpg. I also tried non ethanol 93 octane no difference except a $0.60/gallon higher in price. A seat of the pants feeling was that the higher octane a faster thottle responce, but being retired, I'm not in a hurry. When the HHR is floored, it will still hit 6500 rpm quickly before shifting.

So 93 octane E10 isn't worth the 25 cent/gallon higher price in my opinion.

about every third or fourth tank of 87 I put a bottle of sea foam in the tank seems to keep things clean and running good I average 32 mpg of course my 60 mile daily commute is 98% highway at 70 to 72 MPH

I have a 2.4 with Auto Trans, I run Shell Premium only.
I'd rather stick with a large name brand gas and Shell stations are plentiful around here. The 2.4's call for Premium so I use it.

Any of my other cars over the years, I just filled up on the cheapest gas around, but most of them were just well over 75,000 mile cars when I bought them just for work use or daily beaters that I did not care much about. (No long term caring to keep them around)

I plan on keeping my Panel around for awhile so I use whats recommended to use and the extra octane can't hurt.

And once I install the Supercharger it will be a must use anyways, along with synthetic oil like Mobil 1.
So I am already in the habit of going to Shell and filling up with the best premium they have.

Years ago we had Martin stations that sold Purple Martin Racing Fuel at a couple of their stations. Wish that was still available.

Compression is 10.4:1 on the 2.4L.
Compression is 10:1 on the 2.2L.
The difference is of a .3 ratio.

I wonder exactly WHY the premium is required for the 2.4L. This, to me, doesn't seem substantial or totally necessary, especially with VVT.