Not just another "stupid gas mileage" question...

While most threads about gas mileage ask about improving it, I'm striving for something different -- we're dealing with "change over time;" a genuine differential here! Anyway, let me explain this rather unusual situation.

I bought an XJ last October out of a junkyard. It had been totaled, but it was salvagable. I restored the Jeep to like-new condition ($6,000 later :confused1 ), replacing both exterior pieces and mechanical things.

Before tearing into the vehicle, I noticed that the trip computer was registering 16.3 mpg average -- this information is stored in non-volatile computer memory, meaning that it's saved even if the battery is disconnected. A rough indication of what the previous owner was seeing with respect to gas mileage, essentially.

To date, I've been getting 14.7 mpg on average, having put about 400 miles on the XJ since its revival. What really gets me is that I replaced many things while it was under construction... filters, all ignition components, sensors, etc. I also ran a can of BG 44K fuel cleaner through the tank. You'd think that I'd be seeing at least equivalent economy, if not better!

What do you think would cause something like this? Could something have "changed" in the eleven months that this thing hasn't been driven?

The only idea I have is that the front oxygen sensor died, but isn't reporting a fault to the ECM. I already replaced the rear sensor, as I couldn't remove it from the exhaust when I replaced the cat and muffler.

Driving style. JIM.

that sounds pretty bad to me either way. I get 18 or better on both of mine, one a 99 one an 88. What year, miles, tires, gears, tranny, city or highway, etc? I think Jim is probably right though. Drive it like you grandma

Matt

el_chupo_ said:

Drive it like you grandma

Click to expand...

That's the funny thing. I do. I think I've had it above 3000 RPM twice since I've been driving it, and I always let the transmission shift into a higher gear when possible. I drive it lighter than any of my other vehicles.

It's a '98 with 93,000 miles and 235-75R15 tires. Tranny is the typical AW4, but I'm not sure about the axle ratio. I did a compression check tonight, just for the heck of it, and each cylinder is at 170 psi, +/- 5 psi. Seems perfectly normal.

This is all city mileage, as I haven't taken it on any long(er) trips yet. It's a little disheartening... my YJ with 33s, five inches of lift, and four cylinder gets 17 mpg -- and that's running out the gears since it's so underpowered. It's floored 80% of the time, haha.

gas milage on my 97 with 120K+ is anywhere from 13-17 city and 19-23 hwy, depending on how I drive it. If I drive it like a grandma, rarely getting it over 2200RPM I can get around 16-17, but the way I normally drive, 3500 RPM first and second gear I get around 14. -

PS I seemed to get a decent boost in mileage when I cleaned the throttle body and had the fuel system cleaned.

B

Many thing effect MPG,

Driving style,
Front end alignment,
Plugged/resticted Intake/exhaust,
O2 sensor,
Correct and properly installed "tune up" parts,
Tire size, tread, and pressure,
Vacuum leaks,
Just to name a few............

iroc86 said:

This is all city mileage, as I haven't taken it on any long(er) trips yet. It's a little disheartening...

Click to expand...

Yes, but it's normal. EPA for the 96-01 4.0L AW4 combo was 16 city, 21 hwy. Most folks get 15mpg city.
,Ron

14.7 in the city is pretty good. The previous owner probably had a much higher percentage of highway cruising, which explains the difference. I have never measured mine, but it seems like the darn thing gets about 12 in the city. I know it gets 19 on the highway, its mostly stock, no lift.

My daily driver is a 2 wheel drive/4 banger/manual transmission XJ with no frills. I try to feather the pedal. I just checked my mileage last week and got 25.46mpg out of it. Yay! :thumbup::thumbup::thumbup:

And if I loose my fat rump, I'm sure I'd get better mileage :chef:

However, I'm addicted to oreos....help!


.

Interesting stuff. One thing that I hadn't thought about was wheel alignment... I guess even if it tracks straight, there's the possibility that the wheels are turned into each other such that rolling resistance increases. Even for suffering from a front-end collision, the XJ tracks just fine. I might want to get that looked at.

I'm still leery about that front oxygen sensor. Maybe I just need to replace it and get the notion of a "possible" failure out of my mind... though I really hate throwing parts at a problem, especially if it's non-existent!

In my 89 auto XJ i was under the impression that it got around 17 mpg on average. I recently swapped in a 93 HO motor and my mileage went down to around 10 mpg. I did not know that a lot of poeple are used to 14-15 mpg. I will hav eto get my heep alligned and recheck my vacuum lines and hopefully it will improve; but it's good to see that I'm only down about 4mpg on average!

I swear, there is nothing wrong with your vehicle. Even if the O2 sensor is bad (it isn't) the miledge would not drop a whole lot. Further, lets say you spend $300 on parts and up your miledge by 1.5 mpg to get to the 16.3 or whatever. Wow, the extra miledge would take what, 5 years to pay for itself?

Jackhill442 said:

lets say you spend $300 on parts and up your miledge by 1.5 mpg to get to the 16.3 or whatever. Wow, the extra miledge would take what, 5 years to pay for itself?

Click to expand...

Yeah, I know . I'd actually recoup the costs in about seventeen months (having spent $300), assuming that gas stays at the same price. It's actually more beneficial to worry about mileage if you're on the lower end of the spectrum, as there is a point of diminishing returns (it'd be worthless to try to gain an extra mile per gallon at 20 mpg; it'd take almost three years to pay off!).

It could be diet, where was the title from. The gas in Oh. and PA. sucks, Ohio don't even test the stuff. Also I think that PA allows more Alcohol (up to 20%) and that stuff burns fast.

Well, it was last registered in Hidden Valley, PA, near Somerset (about forty miles east of me). Since you mentioned the location, I took a closer look at the CARFAX report I have for this thing. Seems like it's been all over the place... northern PA, eastern PA, southeastern PA; even Ohio. And it ended up in Titusville after it was totaled... about 175 miles from where it was last registered! Insurance companies confuse me. Anyway...

I agree about the fuel quality around here. That was the first thing that came to my mind: "What the heck are they putting in the gas now?" My Wrangler went down a full point between fill-ups; it had been at a constant 17 mpg since May. I wonder if there's a way to find out which gas stations use certain additives. It would be a lot easier to find higher-quality fuel.

More about gas mileage, how about 200mpg, there nothing for sale here, just information.
http://byronw.www1host.com/

langer1 said:

More about gas mileage, how about 200mpg, there nothing for sale here, just information.
http://byronw.www1host.com/

Click to expand...

That page has a lot of interesting information. Seems like the guy really did his homework, too.

Kinda sparked my imagination... it would be neat to try gasoline vaporization in a testing environment (i.e. lawnmower) to see if it really works the way they say. I might do that sometime.

iroc86 said:

I agree about the fuel quality around here. That was the first thing that came to my mind: "What the heck are they putting in the gas now?" My Wrangler went down a full point between fill-ups; it had been at a constant 17 mpg since May.

Click to expand...

Here in Western PA, we just switched to "winter fuel" on Sept 1, I think. Winter blend is basically REAL, BURNABLE GAS... but with the oxygenated crap (used to be PTFE)... as opposed to the "low volatility" summer blend.

Most of my cars have gotten a mile or two less per gallon on the winter blend. My old carbureted Oldsmobile was the worst... it'd go from 19-21 down to 16-17....

Den