My first tank (provided by the dealer) was 87. After I read the owner's manual, I started using 93 and I could tell the difference in pep. My gas mileage also increased about 3 mpg with the higher octane gas.

 

The very same with me but I use 91

 

I use 91 also. May drop down to 89 fr day to day stuff and use 91 on trips

 

Can you buy the 89 and use an octane boost to get it to 91 or 93? Or is it better just to buy 91 from the gas station?

 

Why would you do that? Would that not be more expensive than just buying the proper grade at the gas station?

 

Why not buy 93, don't have 91 by me, and then add octane booster?

Went to a station in sothern Missouri and they had FIVE grades; 87, 88, 89, 90, 91.

 

I didn't realize they recommended premium gas when I first bought my HHR and was using regular. Once I found out I had just filled the tank so I added an octane booster and got probably the worst mileage I have gotten period. I have since used premium and found a 4 to 6 mpg difference in my mileage so I am sticking to premium as I feel it pays for itself with the increased mlieage.

 

I'm running a bit of a test right now. Have run 92 in my 2.4 for 3 months and have been getting about 26.5 MPG. Yesterday I filled up with 87. So far it's not looking good for 87. I'll usually get about 27-28 MPG on the first run to work on a full tank. Today I got 24.5 during a typical drive in.

I'm going to run 2 full tanks and see what I get. I'll update when done.

 

You need to be VERY careful with octane boosters and gas "additives". Some can do damage to your vehicle.

For more info, read your owners book.

 

Well you sound just like me !!!! I haven't progressed to the point that I can post pics either. LOL

At least tell us what color you bought. Mine is Silverstone.

As far as the octane number of fuel to use. I started with 87 from the dealer.
I beleve my DIC fuel range showed around 370 or so. With 91 it shows around 430-440. As far as performance, I can't tell that much difference, but the HHR can. Higher octane generally is a higher filtered fuel. It burns at a more controled rate, yet it is a hotter burn (more thermal btu's) per ounce of fuel. It runs cleaner in the combustion cycle as well as the exaust cycle. If you run Chevron's 91 octane you get the additive "Tecrolene". It has proven to keep the injectors clean as well as the combustion chambers.
Less deposits.
Welcome aboard - Good luck and be sure to join the forum as a prem.member.
A lot of good info here.