Dark Angel

Just curious...I own a '93 Cherokee Sport 4.0. Up until recently was using 87 octane but was getting engine pinging. Someone suggested I upgrade, so I went to midgrade but still get a little bit of pinging once in a while. My question is, should I go to the highest octane gas for my engine (or will that be too high)? This is my first Jeep and I want to do what's best for it. What do you all use/suggest?

andrewmp6

What gas are you using tho?Not all brands are the same some are crap.I would have a mechanic look at it could be a few things why its spark knocking like that.

salad

You should be fine on 87 OR of any of these brands: http://www.toptiergas.com/retailers.html

If pingig on 87 in a 4.0 you need to clean the carbon buildup out of the combustion chambers. Search around here as there are various ways.

scottmphoto

You might try some non-ethanol stuff.

http://pure-gas.org/

Dark Angel

Andrewmp6, I try to stick with Arco...I'm also in California, so our gas is all unleaded...not sure if that makes a difference. Upgrading to the midgrade seemed to help the pinging, but not 100%.

Salad, thank you for the tip on cleaning the combustion chambers...I will do a search for the "how to". I did clean out the throttle body not too long ago, and it was pretty built up. Also, thank you for the retailer link...didn't see Arco on the list, but I thought they were affiliated with BP?

Scottmphoto, thank you for the link...I've never run anything but commercial gasoline in my Jeep.

salad

Not sure as I'm not in the US, I do recall a few people on here complaining that their fleet vehicles ran poorly on Arco and they would fail emissions tests (similar on Wal-Mart), so I assume they're very light on detergents.

rackem

you should not be pinging on 87 california grade arco at all.

you have carbon build up in your combustion chamber i can almost guarentee it. unless the PO of your vehicle did some engine upgrades like upped the compression ratio of the motor.

DieselDaze

my '88 MJ did the same thing, very temperamental... being native californian I'm familiar with arco, mobile, 76 etc... without fail it would always pinged with mobile, i didn't use arco cause there were many rumors of water with their gas..

what you need to do is take your xj and have the injectors cleaned, it takes a couple hours but its well worth it... cost maybe $60... after I had it done I could use any gas with no pinging...

otherwise just use chevron or 76 out there and you should be ok..

Dark Angel

Salad, thank you, failing emissions tests on Arco gas makes sense too, as mine has failed as well...seems I always have to dink around with the engine in order to get it to pass smog. It usually fails the first time.

Rackem, as far as I know the po replaced the engine with a brand new one (not rebuilt) at 100k...I bought the Jeep at 125k. Engine is totally stock.

Dieseldaze, thank you for the info about California gas...hadn't heard about Arco and water.

Okay, sounds like the problem is engine buildup and I need to change the brand of gasoline I'm using. Okay, will change from Arco for a while to either Chevron or 76 and see how it goes, and will also look at cleaning out the injectors and combustion chamber. Thanks so much for your help, guys! xo

basegrinder

Ha. maybe in SOME places there is a difference....but keep in mind how FEW refineries there are in the US. 143 total.

Go to any one of them and you'll see trucks from EVERY brand of gas picking up gas from the same hookup.

salad

You realize were talking about detergents, which are added sometimes in the truck or at the local station, right? Regardless, 143 refineries is extremely diverse. Eastern half of Canada has ONE, and we see differences between brands.

That's like saying that you saw the same Sysco truck go between two restaurants, therefore you must be able to get a Wendy's burger at Subway.