Which Fuel?

[Don]

Need Help I cant seem to get a wright answer on this one even from a jeep dealer,I just got a 1993 Grand Cherokee LTD 5.2 Liter Does anyone know what grade fuel is suposed to be used? super or regular? thanks for anyones help.

 

[Tug-n-pull]

pointing a pinion

Use a tank of regular if you have an octan knock, next fill up use middle grade if you have a knock, go with super. tug

 

[pinaplebob]

We also have a 98 grand cherokee.....and we have to put mid grade in, or it will ping and not run very well.

 

[graewulf]

Driveline vibration????????????/

I run regular in my 95 ZJ with no problems... make sure you have a good clean air filter and its maintained and you should not ping.....

 

[mingez]

Lil' question about the PING. I've always heard that is a way to diagnose insufficient octane, but why does it ping????? I never understood this.
Please don't flame the inexperienced guy if this is a dumb question. :wink:

 

[graewulf]

Lil' question about the PING. I've always heard that is a way to diagnose insufficient octane, but why does it ping????? I never understood this.
Please don't flame the inexperienced guy if this is a dumb question. :wink:

my understanding is it pings because the engine is advancing the spark to the point where the engine is firing before the valves are fully closed... causing a ping through the intake valves. Octane slows down the burning of the fuel, so higher octane wil not burn fast enough to ping under this condition.

 

[randomjeeper]

i've got a 94 grand and i use the middle one (89 i think), no problems.

 

[XJNick]

On my wrangler I usually use 87 octane but use 89 octane every 5th or 6th tank. I also Used to to the same with my cherokee...

-Nick :!:

 

[TwistedCU]

At these prices, gasahol would be good. Hey, how come the gas price is so high? Didn't we win that war???

 

[randomjeeper]

how much is gas where you are?

 

[bchcky]

use diesel :lol:

 

[bchcky]

btw, i realize this thread started in nov. but i was really bored and looking through old pages in the forum.

 

[Tug-n-pull]

how much is gas where you are?

different every day. Reg. runs from 1.45 to 1.60. Try to need it only on the 1.45 days hehehe

 

[Junkpile]

Lil' question about the PING. I've always heard that is a way to diagnose insufficient octane, but why does it ping?????

The ping is pre-ignition, or the ignition of the air/fuel mixture before the piston reaches TDC and begins it's downward travel. The explosion pushes down on the piston as the crank is trying to push it up. The pinging is like hitting the piston with a little hammer every other time it comes to TDC. Severe pre-ignition can blow holes right through pistons. The octane rating is nothing more than the fuels ability to resist detonation. The higher the number, the less likely the fuel is to ignite prematurely.

Our 02 WJ with the 4.0 spark knocks at around 4,800rpm with regular, so I try to run at least mid grade in it.

 

[Snitty]

you want the fuel/air to ignite (NOT detonate) JUST as it is returning from TDC and going back down on the power stroke. anything before that will cause ping...