there is a sticker inside the fuel door that says to use 91 grade but what will be effected if we use 87?

 

If it says required use it, if it says recommended use it if you can afford it.

Or, look in your Owner Manual. Pages 6-5 and 6-6.

Or, argue with GM.

 

My '08 2.4 says 91. I use 91 most of the time . Last year on a long trip I put some 87 in it and lost 3 miles per gallon. Now I use 91 Top Tier all of the time...john

 

It appears your HHR has been tuned at one time , concurrent with the GMPP performance exhaust! Run the 91, or risk internal engine damage.

 

Mine is tuned for 93 octane...

 

I haven't tuned Gregg but still run the recommended 91 (in reality 93) octane. I found that not only is MPG better but the true power potential of the 2.4 is brought out with higher grade gas. Trust me. It aint no race car, but Gregg is pretty darn good at getting out of his own way.

 

here is the sticker. do they all have this?

 

No. See post #4 & #2.

"Required" is the same as "ONLY!" in my world.

 

No, they don't all have that sticker. Read that as 91 octane "required". Your HHR has been tuned and needs the higher octane fuel. (Unless some maroon flashed it back to stock before selling it)

 

High-Test. Is that a retro sticker from the 50's ?