I run 93 octane as much as possible. I have not had any problems running lower octane, but I get better mpg's and more power running the higher octane.

 

It's funny if you watch the fuel delivery trucks. They will stop at a "brand name" station and dump a load, then go to a "no name" station that is 2 or 3 cents per litre cheaper and dump from the same tank. I remember seeing a bumper sticker that said

I would push this car a mile
and do it with a smile
and be happy when I pass
on Petro Canada Gas

I can't believe how many people still get gas there for more money

 

I have the bigger engine and it says to use premium...

 

See:

https://www.chevyhhr.net/forums/general-hhr-4/premium-gas-2-4-engine-12641/

 

I have the 2.2 engine, so it's 87 for me.