93 Octane??

Yes, the potential is there. The how is from detonation.

You aren't wasting your money following the manufacturer's recommendations for your vehicle. You would waste a lot more money by not following them.

Matt

Chances are that you won't hear either detonation or preignition over the sound of the engine, unless it is a loud knock. Your engine may be equipped with a knock sensor to retard the spark however. This should avoid damage to the engine, but possibly cause you to lose power. If your manual calls for

HB2 wrote:

Sure, if you don't really care much about your engine. You may or may not hear it. If you didn't want to buy high octane gas, why did you buy an engine that requires it?

You can also not change your oil and listen for signs of mechanical failure...

Matt

Matt

Give the guy a break, not everyone knows the importance of using the correct octane fuel. All he needs to know is that he really must use the correct octane gas. Using 89 at best would give him worse fuel economy and performance but at worst could seriously damage his car's engine.

G.

ridiculous???

The more this gentleman posts, the more I realize how much misinformation he spews. If he knew anything about the engine/injection system used in this vehicle it would really surprise me. Nomen, tell us all how to time this engine and how you are going to retard the timing. This had better be good.

Denny

Actually, Nomen Nescio's post on this subject is quite comprehensive and accurate. Also, High Octane gas is not a better gas product, or a higher quality gas product, it merely is designed not to ignite as easily as a lower octane fuel.

Richard.

misinformation

Ok, then can you tell me how to set,adjust,retard timing on a motor that it is not adjustable?? Ole Nomen's ideas may work on pre 80's systems, but not on anything new.

Denny

No, I think it is limited to some of your thinking and some of your posts.

I, and at least one other person, told him why this was a bad idea in an earlier post. He came back again still looking for a way to do something stupid. I was simply making an illustration, that I hoped he could understand as he's obviously not very mechanically literate, as to how stupid this is. As you say, it MAY only cause him a performance loss, but it CAN, under the right circumstances, cause him serious engine damage.

Also, after the profane message he sent to my home email address, it is obvious that he not only isn't too bright, he's also gutless wonder.

So, HB2, you are right, to quote from your email, misspelling and all, "You response tells me you are an asshole.", so you'd better ignore my advice and run the lowest octane gas you can find. Some places even sell 86, maybe you can find some of that. Enjoy your Jeep!

Matt

It is designed not to burn so quickly. Ignition is more a function of RVP than octane.

Matt

The engine computer controls the timing and can easily retard it as required. Nomen was correct about this. He doesn't have a clue as to what makes gas good or bad (hint, it ain't octane rating), but he was basically correct on most of the rest of his post.

Matt

Matt, yes the computer controls the timing and can advance and retard it as per programmed. But how does it know when to retard it due to preignition? This engine does not use knock detector. On this engine, the dist is indexed. Moving the dist does not advance or retard the timing. Ole Nomen is correct if we were talking about pre-mid80's engines, but not about this one.

Denny

It is ok to use higher octane fuel in a vehicle designated for use of 'cheap stuff'.. however, it is a waste of money, as no extra performance will be gained.. use of cheap fuel in a vehicle designated to run on higher octane will eventually lead to problems.. if you are so cheap, you should have gone for one of the lesser engine variants..

-- History is only the past if we choose to do nothing about it..

You might want to take a look at this..

-- History is only the past if we choose to do nothing about it..

Thanks for the link. But note that it is full of very inaccurate information. A high octane fuel in a motor not designed for it can be harmful! It is not clear cut because the methods to achieve a high octane number are quite varied. But some of the additives used in some of the products can degrade performance at the least.

Richard.

As Mic Canic already posted, if this Jeep is a V-8 from 1998, it's undoubtedly the "special limited" V8 that Chrysler put out only in that year. The 1999 and later are redesigned. If anyone were to bother to look in any Jeep-specific forums they would find this engine discussed, it was apparently designed (in my opinion) as a plushmobile Jeep for overweight suburb dwellers who never go off-road (ah, the thing has an _automatic_ pansy I mean transy for God's sake) and who want to pretend they are driving a "souped up" Jeep. So it does not surprise me a bit that the Owners Manual calls for high-octane gas. Undoubtedly, Chrysler designed it that way (since they could have easily put a knock sensor in it) to add to the "special limited" appeal.

Ted

How and why is it harmful? I've heard this claim made before, but I've never seen any logical reason given. And I've never heard it from a credible source such as an auto maker or gasoline maker.

Matt