Question about gasoline...

Okay I've told my story about having a messed up Jeep, taking it back, buying a different one, and LOVING every second with the new one.

I'm wondering this:

Right now I give the truck 87 octane, and I've been reading a lot of things online about people hearing a lot of things with the engine with this octane. I do hear some weird noises, and I want to know how much performance-wise I will gain from going to 89 grade?

Will I feel a HP/TQ gain?

Will it reduce engine noise?

Will I hurt the engine at all by mixing the gas (non-empty tank), or will it cause harm to the engine/truck in any way? With the first Jeep, I filled it up with 89 after it had 87 in the tank and about 5 miles later at 60 MPH it blew gaskets, etc. So will 89 hurt it?

The last question is the most important. Sorry if the questions sound dumb, but I'm only 16... Thanks for the help-- as always.

Actually octane number is basically the speed at which fuel burns. The higher the octane,the slower its burn rate and its ability to keep from preigniting(pinging). If you look in your owners manual you'll find a recommended octane to use,what the engines computer is tuned to work with but it isnt that critical between 89 and 87. if you hear pinging then move to a higher octane.Too high an octane wont damage like too low an octane.Extended pinging will damage an engine.
Happy to help,
Gary D.

What types of octane do you all use in your trucks?

Just wondering...

I run 93 but I have a 4.6 stroker motor, i tried the cheap gas and it 'pinged' like crazy, so i went to 93 in fact i always ran 93, but thats me....

93? HAHAHAHHA

That's great. In shi*ty maryland, we only get 91 max....

Gr on you!

Gas

Darwin, I have an 88 with 218k and I use 87 all the time without any problems. HTH
Dave

Use 87 all the time. Just try to stick to the same brand all the time, no problems what-so-ever.

What year and how many miles ???

If the jeep is higher milage and you are getting alot of pinging then it may just require the following. Get a new set of plugs, cap, rotor and wires, new O2 Sensor. Pick up a can of 'top engine cleaner', some spray carb/Fuel injector cleaner and a large can of Chevron Techron. GM made a very good top engine cleaner but no longer produces it, you might get lucky at a GM dealer and find one who still has it in stock. Another product called 'Sea Foam' is sold by NAPA, this pretty much does the same thing, follow the directions on the can and allow the manifold vacumn to suck it in thru a hose.
Step1. Using the 'top engine cleaner' or 'sea foam' follow the directions on the can. This will remove carbon build up in the cylinders, this carbon build up is what causes pre-ignition, the carbon is still partially burning when the piston is on the compression stroke and starts igniting the fuel before the plug fires, result is a 'pinging' or 'knock'.
Step2. Dump the can of Techron in a full tank of normal regular gas.
Step3. Using the spray can of carb/Fuel injector cleaner clean the throttle body out. Do this with the engine running and try not to get any into the sensors on the throttle body, most Carb/FI cleaner is NOT plastic friendly. Once you have everything nice and cleaned out start with replacing the plugs, wires, cap/rotor and the new O2 sensor or sensor, my 98 has two, one on the exhaust manifold and one further downstream underneath by the cat and muffler.
If you are doing alot of around town driving on a daily basis you need to get it out on the hiway and get it up to hiway speeds for a couple of hours. The 4.0L is a slow turning motor and is very susceptiple to carbon build up. One thing I kinda skipped over is the fuel injectors, you can either replace them with new ones, have them professionally cleaned or buy the injector cleaner kit from 3M that is sold by NAPA for around $100 with adapters. The 3M kit is a long term solution if you plan on keeping the Jeep, the cleaner/fuel refil cannisters cost around $22 ea, generally a once a year thing. It does a good job and the kit comes with adapters that you can use on other fuel injected vehicles if your family or friends have them. The cost of the kit is about the same as the cost of having them professionally done.
I also strongly recommend, as most here will also recommend, GET A FACTORY SERVICE MANUAL for your year Jeep, much better than a chiltons or Hanynes manual and it goes into quite a bit of detail. The FSM will pay for itself over and over and over again.

RichP

I run 87 in mine all the time, no problems, I've tried 93 for the hell of it, made no difference, maybe increade gas mileage a tiny bit, but not enough to warrant the extra 20 cents or so per gallon.