I keep telling people that algae is the way to go.

 

It makes sense that altitude plays a role in gas mileage because of air density. Up here in Wyoming a person can go from less that 5000ft to over 10000 in a relatively small distance. If you set cruise control on long stretches of interstate without adjusting it and either gain or decrease altitude you will notice that your speed will eventually be different than where you set it because of air density. I think the fact that the 85 octane is available anywhere up here has to do with the small population and low smog as well as the altitude. Any other insight anyone?

 

Pretty much everywhere in Wyoming that I have gone, you can find E0 gas easily.
I think when you got 22MPG you must have been driving east, only in Wyoming you can go highway speeds uphill in neutral as long as you have a tail wind.

 

Why does this thread keep going back and forth between E85 (85% ethanol) fuel and 85-87 octane gasoline (10% ethanol) fuel? They're 2 different things. E85 fuel would be bad news in the XJ but 85-87 octane fuel would be fine.

 

I was wondering the same thing. I think somewhere along this thread someone must have mistakenly thought we are talking about E85 when instead we were talking about 85 octane. Easy mistake to make if you have never encountered 85 octane i guess. It wasn't until I moved from Phoenix to Wyoming that I encountered 85 octane, before then I didn't know that anything below 87 existed. I am amazed that this thread is even still alive but I guess it can't die if I keep adding comments like this.

 

I've seen 85 octane gasoline at the pump numorous times but never seen a E85 pump....are they different? Can u accidentally put a E85 pump nozzle in the XJ tank filler?

 

Yeah they are different. E85 is less costly at the pump however will give you less power and decreased mileage so no real savings in the long run. Not sure if you can put an E85 nozzle in an regular gasoline filler.

 

I'm pretty sure that an E85 nozzle will fit a standard fill opening, but you shouldn't run it in your vehicle unless it was designed for it. Newer "flex-fuel" vehicles can run it, but your XJ probably won't like it at all.

 

An E85 nozzle is the same size as a regular gasoline nozzle. The difference is the E85 nozzle is usually yellow as is the filler cap on flex fuel vehicles.

 

I have lost 2 heads to cheap gas with too much ethanol. The 4,0 in my 98 XJ and my old B-250 Dodge with a 225 and 1bbl carb. There is 1/3 LESS energy in ethanol, and it will make a motor run so hot the head will warp. The XJ i milled the head and replaced the gasket. The 225 was TOAST!

 

Yeah, because the 225 slant six was NEVER made to run ethanol...

 

You are a retard. Look me up when you are in Northwest Arkansas and you can pay for a tank and see for yourself. Last fill up I got 23.5 mpg. A one hit wonder on a Jeep forum.... youre an idiot. I cant believe you would post 4-5 times just to say that I am a liar, and ask if anybody actually believes me. All I am trying to do is offer help to someone who finds this site through a Google search with the same problem. I cant believe anybody even responded. If you dont believe it, fine, I am just putting it out there that that was my problem and if you don't believe it, keep filling with ethanol if the same thing happens to you and start replacing stuff that does not need replacing until you drive yourself crazy. You make me want to never visit this forum again.

The ethanol caused it. Just because that sticker says may contain up to 10% does not mean thats all that is in there. Buy a test kit and you will see that some gas, because of the way it is mixed, can have up to 20%. Go see for yourself.

I was in Utah a few years back and was cruising around Moab at 40-50 mph, and got 27mpg. Dont believe me? Who cares.

 

Thank you! Finally someone else realizes that it does burn hotter. The nuked 225 is proof. Those engines were as tough as AMC 258s.

 

I have the original window sticker for my '96 Sport 4.0L auto and it was rated 15/19. Over the 7/4 weekend we drove from south, central Pa to NC and back 860 miles. Of that about 350 miles was 70mph on I-81, and much of the rest was either rural 2 lane or the Blue Ridge Parkway. We averaged 21.7mpg without accounting for larger than OEM tires (235-75-15 vs 225s). This past weekend I ran 55 miles on the Pa turnpike and compared my odometer with their measured mile markings and found that my odometer is -2.5%, so the 860 miles would have been 881 and the mileage would have been 22.2mpg 89 octane. I do have the crossbars in the roof rack, and is stock.

The point is that some 4.0L XJs will deliver better fuel mileage than originally rated. Mine has yielded better mileage with 89 than 87, and 92-93 makes no real improvement over 89.

 

Just curious, but from that last sentence it sounds like you use the computer in the overhead console for your mileage & etc. Is that the case?