I have a 2007 hhr with a 2.4 litre with no owners manual, a person with a similar one claims the owners manual says to burn higher octane fuel than the regular 87 octane what is true? I thought that all hhr's except turbo's would burn 87 octane?

 

Here's the link to the owners manual. Read away.
https://www.chevyhhr.net/forums/general-hhr-4/online-owners-manual-3074/

 

I run primarily 87 octane in my 2.4L engine in my 06. Unless you are going for performance, 87 octane works well. I have tried higher octane and saw no mpg improvements. I have run ethanol free (93 octane) and did notice better response. But at $4.29/gal vs $3.45/gal for 87 octane I don't find it that beneficial, it just lightens the wallet faster.

 

I run 87 in my 2.4, gets better mileage with it.

 

Nope. I have a 2009 LS and it recommends premium fuel, not that I always do that. I usually run 89

 

Yep. Notice the word RECOMMENDED (not REQUIRED). That is what is being questioned here. The Owners Manual states the 2.2 is designed for 87 octane. The 2.4 the recommended is premium but can use 87 or higher without damage.

Yes, you CAN use 87 in all but the SS. Except, again as mentioned in the Owners Manual, if you notice spark knock, go to the next level up in octane. As mentioned by others, you MAY notice a performance difference, also.

 

ok, I have a rough idle thought that might do the trick, I think I got other issues such as piss poor compression readings with this thing. there is a tsb out on these things for the valve guides from what I been told.

 

There are also members that have over 100K, 200K & 300K on theirs..

Do a compression test, or a leak-down test..

 

A healthy Ecotec should have between 155-180psi in each cylinder on a compression test, GM specs state that there should not be more than a 70% variation between the highest and lowest cylinder.

If you find that a cylinder shows 100psi or less, that's a fairly good indicator of an issue with the valve seat, valve, or valve guide.

As sleeper suggested jtuchol, you should also strongly consider a leak down test.

There were problems on some 2007's with loose valve guides for which GM issued a TSB but no recall.

It seems that most of the affected units showed problems early on, how many miles are on your HHR currently?

 

70% difference? I don't think so

That means one cylinder could be at 180psi and another could be at 55psi and that would be ok?

No way!!!

I've always used 10% as an optimum number and if find something was even 20% off, I start looking for a problem and usually have found one