Jeep Repair: 1993 Jeep Cherokee Sport Compression Ratio, jeep cherokee sport, jeep cherokee

Question
Hi Kenji,

I've been searching for the compression ratio for my 4.0 inline 6 cyl. in my 1993 Jeep Cherokee Sport. Couldn't find it anywhere in my "Hanes" manual from Auto Zone. A guy at Auto Zone couldn't find it in any of his manuals either.

I'd just like to know so I could compare it to a chart I found on the internet recommending specific octane grades of gasoline for specific ranges of compression ratios.

I'm just guessing it might be anywhere from an 8.75:1 to 8.9:1.

Do you think my inline 4.0 6 cyl. will run well on 87 just as well as 89 octane?

Thanks.

Mike E.

Answer
Hi Mike,

Is it an HO? I think it should do fine with 87 octane. Are you experiencing performance problems with the fuel you're currently running?  Dude, I'm not so sure we're even getting the true 89 octane we're paying for anyway! That's another story. I'll check on the compression ratio.

Kenji

Hey Mike,

Your 8.75:1 to 8.9:1 is right on the money.

8.8:1.

Kenji