What grade of gasoline should I put in my 94 Jeep Grand Cherokee?

Answer 1

REGULAR!!! and only TEXACO, CHEVRON, or SHELL. they have good quality gas and keep the water and crap out of their tanks. BP/ARCO are the worst except for the independents...

high octane does not make more power, it actually RESISTS igniting!
"High Octane" is not synonymous with "good" or "better", and does not mean that it is better for your engine! And the chances are pretty good you don’t need high octane fuel in your car.

High-octane fuels only become necessary when your engine has a high compression ratio. It’s a very long and complicated story…that the swami will make short.

First important fact that you must accept:

All gasoline, regardless of its’ octane rating, have pretty much the same amount of energy per gallon. What!!! "Sacrilege" you say? Well, actually, some higher-octane fuels have a few LESS percent energy per gallon…so as not to argue over this small point, for the sake of this discussion we will all agree that the automotive gasoline that you buy at the pump, regardless of octane rating, has the same amount of potential energy.

Second important fact that you must accept:

Octane is NOT a measure of power but of the fuels’ resistance to ignition from heat. A higher-octane fuel, under identical combustion chamber conditions, will burn slower.

How can this be? If all of the above is true, how do we get more power out of high octane gasoline? We do, don’t we?

Well…yes we do. Here’s how:

But first you must understand "heat of compression". There is a 2,000 year old fire starting device that still amazes the swami. A length of bamboo was hollowed out leaving one end capped. A stick, about the same length as the bamboo, was whittled down until it fit snugly into the bamboo cylinder. A bit of dried grass or wood shavings were placed in the bottom of the bamboo cylinder and the snugly fitting stick was violently rammed down the bamboo tube. The heat generated from rapidly compressing the air in the tube was sufficient to ignite the tinder.

The same thing can happen in the cylinder of an engine. The piston, quickly squeezing the fuel/air mixture into a small space, can generate enough heat of compression to ignite the fuel well before the spark plug fires, with unpleasant results. If the fuel prematurely ignites while the piston is on its way up, the burning of the fuel, in conjunction with the rising piston, creates even more pressure, resulting in a violent explosion. This explosion is equivalent to hitting the top of the piston with a very large hammer. If you want to be able to see through the top of your piston, ignore those sounds that are usually called: "pre-ignition", "ping" or "engine knock".

What we really want is a very rapid burn of the fuel, not an explosion. And we want the burning of the fuel to take place while the piston is in a better position to convert this pressure into productive work, like on its way down. Think of this burning as a very fast "push" on the top of the piston. Despite the violent noises you hear from some exhaust systems, it really is a rapid push on the top of the piston making the crankshaft go around, not explosions.

So that we can ignite the fuel at exactly the right time with the spark plug, instead of from the heat of compression, they put stuff into gasoline to keep it from igniting prematurely. The more resistant the fuel is to ignition from the heat of compression, the higher its octane rating.

Answer 2

I could add little to the above and that you SHOULD be able to use regular,octane rating depends upon altitude.
However, Jeep eliminated the detonation sensor in 1991 and let the electronic programming handle the control. Some and I restate SOME engines were known to knock if just regular was used under some conditions. If you do not hear gas knock under LIGHT acceleration, regular is fine. If you do, try the next grade up.
Good Luck

Answer 3

check the owners manual all cars and bikes give the recommended octane rating for the engine in the vehicle. all jeeps run on 87 octane. higher octane can be used but gives no notable performance increase. oh i guess there is a deisel jeep now too. so don't put 87 in it. hehe.

Answer 4

Regular 87 octane minimum. Higher octane fuel is a waste of money. I have a 96 JGC w/4.0L I6 engine and I always use 87 octane and it runs just fine.

Answer 5

I would start at the lowest octane (this should be the cheapest) and if your jeep pings, go up to the next highest octane until it dos'nt ping anymore. You shoudn't feel any difference between regular fuel and hi-test

Answer 6

You should have part time 4wd drive so as long as you have that then you can shift on the fly. As long as your driving below 40 mph or around there you can shift into 4 high, but if you need 4 low then you have to make a complete stop and then shift.

Answer 7

put the cheapest you can find and enough to take you to the nearest place to trade that thing in on a wrangler or xj!!! just kidding 87 should be fine if not there will be a sticker inside the gas door stating differnt

Answer 8

87 octane. Your jeep was built to burn this, anything more is a waste. wow 2 pts...

Answer 9

Just run 87(regular) in it