GoreXJ95

Taking my Girlfriends friend to work yesterday, I was running low on gas. So in my haste to get gas I went in an pre-payed. I always get a receite for gas at the same place. I was in such a rush i just hit a button and started pumping and talked on the phone. Well I get her to her work and then I go to work. When I get home i look at the receite and see i got premium gas instead of regular. Did i screw up or what. Could I possibly screw something up. But she is doing better with premium. She is flying down the road now running better then ever but the gas mileage is horrible. Any thoughts, ideas.

Diesel

Its all in your head. Dont even worry about it.

sflxj

Premium gas burns faster so you will dump more fuel and burn it fast at the same time so your consumption will be much more. That explains the bad mileage. However premium will actually help clean the fuel system because it has a higher octane rating. If you look at the fuel cleaners that auto part stores sell it will say "octane booster" so you are running better because it is cleaning the fuel system.

Scotty16

I say you did what I did one time. As long as the premium isnt that expesive I say you done did good.

GoreXJ95

So if i swith back to regular gas and run octane booster it is basically running premium.

Diesel

Yes and no. Burn faster, maybe, burn more complete, no, clean the fuel system, probably not unless its chevron or shell and ethanol free.

Read this OP- https://www.cherokeeforum.com/f2/eve...premium-57809/

GoreXJ95

It seems to be running fine. Runs quiter and faster but bad gas mileage, also its harder to start up.

mcssls

it, at worst will run a little rich. no big deal

Diesel

Mind tricks, fuel has no magical mechanical noise silencer.

No, XJ's are pre-set for 87 octane, knock sensors wont accomodate for higher octane. Air/Fuel will not fluctuate with octanes.

Gee oh Dee

The difference between the 87 and the 91 or 93 octane is so small, esp for a N/A motor, you won't see any gains whatsoever.

The reason some cars require premium is because they have high compression, turbo'd, or supercharged motors. The higher the octane rating, the higher the fuel's resistance to pre-ignition, also known as detonation, or "knock."

sflxj

Basically

I quote NO rdplz: premium does burn cleaner, therefore, reducing wear on engine parts by allowing them to operate smoother. Valves tick and knock due to friction and when that friction is removed or lessened, the noise is removed/lessened. couple options are:
1. run regular and add a fuel cleaner (lucas or gumout). granted, yes, you'll notice your engine running smoother, but that's it (no real mpg gain) and it gets expensive.
2. run premium. this is the best "easy way out" solution. it burns cleaner, giving you a smoother operating engine and slightly better mpg depending on your driving habits.
3. run midgrade and get a slightly smoother engine, and again slightly better mpg depending on driving habits.
4. Go all out. Pull the throttle body, intake manifild, and injectors and clean them all thoroughly. Put it all back together and run SeaFoam through the system. Make sure to do your gas and vacuum. Some people also add it to their oil, but I've never been one to trust this. I've only done the vacuum (through the brake booster) and adding it to my gas. Run the engine, revving it like crazy to get it all through the system (tons of white smoke will be billowing from your Jeep) until the white smoke stops. This cleans out all the carbon in your engine. From here on out, run midgrade. You'll notice an immense difference in the smoothness of your engine, which, will give you slightly better mpg. Just as long as you don't use the power you regained by cleaning your engine out i.e. liberal use of the gas pedal.

Diesel

The XJ is meant to run on 87 octane fuel, the compression ratio(8.1) is not sufficient to properly, compress and combust high test fuel which leads to a depreciated fuel mileage, decrease in power, and extensive carbon build up. Not to mention after years of running a engine your compression decreases dramatically. On top of that, how would it burn any cleaner when the ethanol is creating a varnish over every mechanical part it passes? There are no gains from premium on a engine requiring 87 octane.

GoreXJ95

Well its just how mine runs. But I will go for a long trip and run her to E and fill her with 87

XJcountry

Only thing you'll notice is your wallet getting lighter if you keep running premium.

Diesel

Only 25 posts and hes more knowledgable than most in here