Fsher21

This is more of a curiosity question, but figured it was worth asking. I used to get about 180 miles out of a full tank consistently, mostly expressway and not a whole lot of stops. I notice recently since i am out of school, my driving is different and im filling up at a different station, but I am getting to about 140-150 miles before I have to fill up.

I suppose that isnt a huge difference, but would different driving habits make my mpg vary that much? Some weeks, I can get 180 easily before my light comes on, but others 150 is pushing it. I think my 96' sport has a 13 gallon tank, i could be wrong. I normally fit about 12 gallons in a fill up once the light comes on.

Fsher21

bigvig

Could be the water content of the gas changes. Do you buy it at different places? Yeah, lead foot will KILL your mileage. So will driving into the wind, driving in traffic ("dirty air") or open road, outside temps, altitudes, up hill or down, cruise control on or off, load, last tune up, etc. LOTS of variables.

excess650

I think you'll find it spec'd to be a 20 gallon tank. The problem lies in where the vent is located, so you're not getting it full. I've seen a write up about pulling the pump, and extending the vent upward inside the tank. I may think about doing it when I have to replace the fuel pump.

Fsher21

Yeah i figured it was a good combo of variables, and being that I start and stop it about 4 times a day and drive less than a mile while doing that, I am sure that is part of my problem. Just didn't realize I could vary 30 miles a tank just because of those variables.

Fsher21

ehhh I think it could be maybe 15...but it is a 96' and I have ran it about 15 miles with the light on, and have never managed to cram more than 12.5 gallons in it. When I fill it up, I can hear the sound of the last bit of air coming out before it clicks off. If it doesn't, I make sure to get every last bit in, as long as it isn't to hot out. Need to give it a bit of room to expand though

bigvig

Yeah, but thats only about a 2mpg difference. Not really that much when you think about it. Add to that, running the AC and cruise at the same time will SUCK the gas down. Use AC and cruise in a lot of traffic at 75mph on a windy day and youre getting even less. I bet you when I use my ac and cruise on the highway at 72 mph it makes a difference of 3mpg. If its fluctuating 1-3mpg I wouldnt freak over it.

excess650

I have a '96 that I bought NEW, and am sure it has a 20gal tank. I'll have to check the owner's manual and see what it specs. I don't recall the window sticker indicating that the 20gal was optional, but I'll check. I do have it.

read this:

http://www.go.jeep-xj.info/HowtoFuelTank.htm

Fsher21

very good point once you break it down like that. I didn't think anyone with an xj had working air, unless you include rolling down the windows and the moon roof :P I use cruise on the expressway, a lot though

bigvig

Well, my compressor and system were all replaced/redone last year because the bearing lip on my compressor went and I use it all the time. Cant STAND the heat.

Also, my wife uses the cruise cause she cant maintain a speed on the highway, but I never do. I coast down hills, draft trucks, other cars, etc., and I can use 1/8th to 1/4th of a tank less than her when we travel to my families house, 144 miles on the highway.

cdawall

assuming it is a 4.0L they are all a 20 gallon tank. mine does the same thing at times light comes on with 12 gallons to fill up. tested it out since i didn't believe it was really a 20 gallon tank ran it empty and put 19.XX gallons in from the jeep sputtering out. ran it a week after the light came on. it varying could be the jeep being dumb mine comes on at anywhere between 12 gallons and 14 gallons used. who knows yours could be the same way.

redmuck

you should have a 18 to 20 gallon tank. i drive mine mostly highway and get 200 to 300 miles per tank, after the sensor tune-up. i believe my best was 315 miles.

Fsher21

So I thought for sure I read in the manual about the fuel capacity...Just ran outside to get it, and sure enough, it is 20.2 gallon capacity! so...even though my light comes on after 11 gallons and shows about 1/8 of a tank, you guys think I could just keep chugging to almost 250 miles on one tank? I swear my gauge is on E if I run it 15 miles with the light on haha.

If I knew that, I could of saved a lot of hassle in the past making desperate detours for gas on the way to class after only using just over half my tank

cdawall

yea i freaked out for the first week or so then went **** it lets see what happens carry a 2 gallon jerry can just in case

redmuck

maybe your guage is bad or the sender/sensor?

Fsher21

I thought if I ran my tank dry I would suck all the **** in my tank into my filter/pump and gunk it up? I am all for throwing a gas can in the back and going until it stops, but I don't want to do any damage while experimenting. Is my float thing messed up or something, is that why it is reading funny?