what fuel octane do you run in your 4.0 i6 and why?

235

Asked by Sep 15, 2009 at 04:46 PM about the Jeep Grand Cherokee

Question type: General

7 Answers

305

87. It's the cheapest and the 4.0 is a 35 year old design that does not require anything higher for performance. Anything more than 87 is just wasting money.

2 of 2 people found this helpful.
235

thx for your response. i was making sure because ive heard mixed responses.

165

Don't use 90 octane. Just use Unleaded 87 octane. Using a higher octane fuel is only more expensive, and instead of conserving fuel, it will only burn/use it faster. The inline 6 was only meant to have 87, and it could possibly overwork your engine if you try and go higher. Besides, 87 is the cheapest... why spend more?

3 of 3 people found this helpful.
130

I was told by a mechanic to use only reg (85 OR 87 OCT) and not to use the 10% ethenol as this causes the senors to assume that the engine is running lean and will increase the fuel consumption until the 02 sensor is satisfied. I have a 99 with 83K and has not had anything but regular in it. Still runs exceptionally well.

4 of 4 people found this helpful.
60

i live in sweden and the low octane here is 95,i run my grand cherokee laredo 4,0 on this,no problems,87 or 89 octane can be had in former east europe or russia,but not in the west,95 gives you a lot of pulling and towingpower

20

Higher octane helps with fuel consumption unlike what some say, higher octane burns slower

2 of 2 people found this helpful.

4.0 has dish type pistons and lower compression. In my opinion 87 octane is perfect for a 4.0's factory compression.

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