MellowFellow

I really love my 2000 Cherokee XJ. The 4.0L engine is peppy, and I believe I am using a great engine oil now too.
My question is asked...
What grade of gas do you use in your Jeep Cherokee XJ's with the Straight 6 motor, and why?

Gas is ridiculous right now and it is really taking a toll on my wallet.

When I purchased this 2000 the old owner said he put the good stuff in it, which here in Southern California means 91 octane.

I am considering switching to 87 octane because I was under the impression these motors called for 87 stock?...thoughts?

CHeers

beat up jeeper

i run mid grade here i ct 89 octane you can run the cheap stuff but you will notice a differance in the "peppyness" ive tried em all and really only noticed a slight differance in the seat of your pants feel but to each his own

Basslicks

they do call for 87 stock.

the only reason you should "need" to run higher octane is with performance upgrades like a stage II performance module... or if you have a stroker motor.

since your motor is stock, you can get away with running the 87... just so you're aware though - you will notice a little difference in performance... the fuel isn't hurting anything, just not as much octane, obviously

tjwalker

For a stock 4.0, all you need is "regular" grade of gasoline. That is 87 octane around here.

There is a myth that continues to circulate that using a higher grade of gasoline (unless your engine is designed to run high octane) is better, or a treat for your engine.

That is a pure myth.

The 4.0 is a low compression very basic engine. And it will provide long service life with a steady diet of regular gasoline, which is what the engineers designed it to run on.

With the price of gas being what it is and moving even higher, run regular and save your money that you would be wasting on high octane for other more important things!!

If you suffer from "pinging" on acceleration and running a higher octane helps with this symptom, that indicates that you have a carbon problem on the top end of your engine.

Basslicks

x2

Crazy Amos

I run 91, the difference is only a couple bucks on fill up so I go with the best they have and always Shell. Heck, just don't buy a 20oz mountain dew that week or switch to a cheaper cigarette to offset the extra cost.

Basslicks

but the whole point is... you're wasting your money... the motor is designed to run on 87... 91 isn't gaining you anything

not to mention the fact that you're running shell to begin with - which is a better fuel... so you would get the same benefit from shell 87 as you would shell 91... the octane isn't doing anything unless you advance your timing (which is computer controlled)

Crazy Amos

I don't know enough about gasoline properties and the differences between grades to even have an intelligent conversation so I will take your word on it. Although when I run higher octane it doesn't seem to burn as quickly may just be in my head though...AND if they put 87 in the 91 tank how the world would anyone ever know the difference?

I run it under the impression it burns cleaner, not for the environment but for my internals.

chopej93

i run 87 in my xj i dont see the point in putting the high 93 octane in a motor thats not built for it like i do in my camaro but if i have the money sometimes i like to run 89 octane when i do my injector cleaning feels like it lasts a little bit longer

Basslicks

nah.... Shell, Mobile, BP, Chevron, and I think Hess have the most detergents in them out of all the other gasolines... the detergents help clean your internals... the numeric rating on the fuel is purely for Octane... the higher the octane, the longer the duration of the explosion... but if your timing isn't adjusted for the longer duration, then you're not getting the full advantage of the octane boost.

I'll give you the point that maybe on an older motor there may be an advantage to running mid-grade.... but it's an absolute waste to run premium unless it is a performance-modified motor

Tylerball72

What's your argument? I wanna know. You set yourself up for that.

Basslicks

I'm sorry, i don't understand your question... what did I set myself up for?

Tylerball72

I think I misread the first time, I thought you said I'd give you a point to run mid grade, instead you said that you would understand running mid grade. my apologies.

Basslicks

No worries....

Here's a little excerpt from Wikipedia that explains is better than I can (I think)

"Octane rating or octane number is a standard measure of the performance of a motor or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating. In broad terms, fuels with a higher octane rating are used in high-compression engines that generally have higher performance. In contrast, fuels with low octane numbers (but high cetane numbers) are ideal for diesel engines. Use of gasolines with low octane numbers may lead to the problem of engine knocking.[1]"

Trev1006

I have a few trinkets on my 4.0 mj. Cam exhaust and such. I run premium Sunoco 94 octane in it. If I'm nit around home and use something else, I can tell. My grandpa is a nhra drag racer and all those guys prefer Sunoco fuel too. In my opinion BP is the worst. My grandpa says they put markers in their fuel that can mess up your engine, not guaranteed to mess it up, but he says it can.