Let's talk fuel mileage

[89 MJ]

I know that nobody buys their MJ for fuel mileage, but I am just curious as to what everyone gets with their MJ.

 

When responding, please include details about your MJ (engine, trans, gears, tires, lifted/lowered/stock)

 

I have an 89 with a 4.0 (that has an occasional misfire) with a Peugeot, 4.10s, 3" lift, and 31s. My best (only calculated twice) was 15.6 MPG.

Once I put my new engine/trans in, I will be testing it again.

[75sv1]

When stock and running, I'd calculate 25 MPG. That is an '88 5 spd. Only mod at that point was a Pace Setter header. I think someone but 3.55 gears. I test drove by mile markers and figured my speedo was off a bit. No Tilted Kilt jokes. I figured 23 MPG by that.

[89 MJ]

Just now, 75sv1 said:

When stock and running, I'd calculate 25 MPG. That is an '88 5 spd. Only mod at that point was a Pace Setter header. I think someone but 3.55 gears. I test drove by mile markers and figured my speedo was off a bit. No Tilted Kilt jokes. I figured 23 MPG by that.

That's pretty good. When I have my new engine/trans in, I am hoping for 18 mpg.

[Dzimm]

97+ swap 4.0, AW4, D30/C8.25 w/3.55, lifted 4.5" with stock size tires.

I get 18-20mpg highway depending on the wind.

 

92 4.0, AX-15, D35 w/stock gears (3.07??), Stock height.

I got around 20-22mpg highway when the truck was in this configuration.  No numbers on the new setup yet.

 

 

[JMO413]

88 with 4.0 Ba10/5 4.10 gears 31s I've only ever figured it combined and I end up at 14 ish MPG. 

[JustEmptyEveryPocket]

87, 4.0L, AX-15, Ford 8.8 & D30, geared at 4.10, with ~2in of lift and 31x10.5 BFGs. I average around 16mpg. 

[89 MJ]

9 minutes ago, JustEmptyEveryPocket said:

87, 4.0L, AX-15, Ford 8.8 & D30, geared at 4.10, with ~2in of lift and 31x10.5 BFGs. I average around 16mpg. 

Ok. That sounds similar to my setup. 

[89 MJ]

11 minutes ago, JMO413 said:

88 with 4.0 Ba10/5 4.10 gears 31s I've only ever figured it combined and I end up at 14 ish MPG. 

That is what I got on my first tank, but a lot of time was at WOT. 

[JMO413]

49 minutes ago, 89 MJ said:

That is what I got on my first tank, but a lot of time was at WOT. 

I drive at WOT regularly I would say. My drive to and from work is a whole 2.4 miles. I drive 1.3 miles to the highway on ramp get up to speed just to stop at the stoplight. Then down the highway for a mile and another stoplight. Left into work from the stoplight. So in no way is this good on gas. 

 

[eaglescout526]

I was seeing pretty poor mileage after a couple years of being on the same spark plugs. I was averaging 260 miles per tank or less depending on how harsh I was to the gas pedal. Then after realizing I havent done the spark plugs for a couple years after remembering my comment about how hard it will be to change spark plug one after I installed AC, I was seeing 240 per tank for the year with AC and then it started dipping below that seeing about 220 per tank. Now I should see 260 after this recent fill up with the new plugs. 

[89 MJ]

2 hours ago, JMO413 said:

I drive at WOT regularly I would say. My drive to and from work is a whole 2.4 miles. I drive 1.3 miles to the highway on ramp get up to speed just to stop at the stoplight. Then down the highway for a mile and another stoplight. Left into work from the stoplight. So in no way is this good on gas. 

 

But, no one buys an MJ for mileage lol.  Glad I’m not the only one who loves WOT. 

[89 MJ]

2 hours ago, eaglescout526 said:

I was seeing pretty poor mileage after a couple years of being on the same spark plugs. I was averaging 260 miles per tank or less depending on how harsh I was to the gas pedal. Then after realizing I havent done the spark plugs for a couple years after remembering my comment about how hard it will be to change spark plug one after I installed AC, I was seeing 240 per tank for the year with AC and then it started dipping below that seeing about 220 per tank. Now I should see 260 after this recent fill up with the new plugs. 

Wow! That difference is larger than I thought it would be. 

[eaglescout526]

Yeah its quite the difference especially when you don't change your spark plugs when you should. I accidentally reset my trip-meter when I was at 36 miles and I am at 130 miles with little under half a tank left. Damn, 166 miles from a little over full(I blame the sender and 16 gallon tank) to a little under half is good for the 2.5L. And I only drive about 8 miles to and from work which I feel isnt enough distance to justify good mileage but hey, as long as I don't have to fill up often.

[fiatslug87]

Well, here's what I have from about 2 years after purchase to this year (from 37,000 to 260,000 miles), probably 98% of all fill-ups.

CMNCHE1: 1990, 4.0L, AX-15, 2WD, 3.07 gears, 235/75/15 tires.

From first day of purchase (from 190,000 to 245,000 miles)

CMNCHE2: 1989, 4.0L, AW4, 2WD, 3.56 gears, 235/75/15 tires.

 

[jdog]

15 - 21 depending on whether its highway or city stock 4.0 w/ 235 tires and ax 15, volvo inj and meanlemons throttle body

best is like 24

[89 MJ]

8 hours ago, eaglescout526 said:

Yeah its quite the difference especially when you don't change your spark plugs when you should. I accidentally reset my trip-meter when I was at 36 miles and I am at 130 miles with little under half a tank left. Damn, 166 miles from a little over full(I blame the sender and 16 gallon tank) to a little under half is good for the 2.5L. And I only drive about 8 miles to and from work which I feel isnt enough distance to justify good mileage but hey, as long as I don't have to fill up often.

Same for me. I drive about 9 miles to work. 

 

7 hours ago, jdog said:

15 - 21 depending on whether its highway or city stock 4.0 w/ 235 tires and ax 15, volvo inj and meanlemons throttle body

best is like 24

Thanks!

7 hours ago, fiatslug87 said:

Well, here's what I have from about 2 years after purchase to this year (from 37,000 to 260,000 miles), probably 98% of all fill-ups.

CMNCHE1: 1990, 4.0L, AX-15, 2WD, 3.07 gears, 235/75/15 tires.

From first day of purchase (from 190,000 to 245,000 miles)

CMNCHE2: 1989, 4.0L, AW4, 2WD, 3.56 gears, 235/75/15 tires.

 

Ok. Thank you. That’s quite the variety. 

[JustEmptyEveryPocket]

8 hours ago, fiatslug87 said:

What the heck happened to CMNCHE 1 from 1998 <--> 2000? CMNCHE 2 looks like a much better statistical layout. Easy to put the best fit line on that one. 

[fiatslug87]

3 hours ago, JustEmptyEveryPocket said:

What the heck happened to CMNCHE 1 from 1998 <--> 2000? CMNCHE 2 looks like a much better statistical layout. Easy to put the best fit line on that one. 

EGR and O2 sensor problem that I finally resolved after failing the biennial Smog test in 2000. Well, CMNCHE 1 is a manual, sometimes I drive it harder but overall it still gets better gas mileage.

[BlackComanche89]

18 mpg on the last trip on highway, it was close to 400 km   average speed 90 km/h 

 

My monthly average is about 14 mpg 

 

89 4.0 original.

[AZJeff]

On 10/8/2020 at 12:05 PM, Dzimm said:

97+ swap 4.0, AW4, D30/C8.25 w/3.55, lifted 4.5" with stock size tires.

I get 18-20mpg highway depending on the wind.

 

 

 

 

I have a similar setup, except my lift is about 3.5”, and I get about 18mpg on the road.   In town, it’s about 13-15🥴

[SVPete]

I get around 20 MPG.

 

1988, 4.0L, Peugeot 5 speed manual, 3.08 rear axle, 4WD, P235 tires. 232K miles on engine/drivetrain.

 

I drive to and from work, about 12-13 miles, at maybe an average speed of 40 MPH.

[btipsword1]

 92 4.0 AW4 lifted 7" on 35s.  Factory 3:55 gearing gives me about 5-8 mpg :)   - I should note, I literally got on here this morning to look at gearing info and came across this thread first

[89 MJ]

10 minutes ago, btipsword1 said:

 92 4.0 AW4 lifted 7" on 35s.  Factory 3:55 gearing gives me about 5-8 mpg :)   - I should note, I literally got on here this morning to look at gearing info and came across this thread first

WOW! That mileage sucks. Sorry for being blunt but that is absolutely terrible. I'd recommend 4.56 gearing for your truck.

[87MJTIM]

Now that I have fixed and exhaust manifold leak, I hope the mileage will improve to ~20.  I have been running 14 mpg.  The REM was telling me that I was running in open loop with LT fuel trims at 166.

 

I now run in closed loop and LTFT now running 114 (and dropping).

[89 MJ]

7 minutes ago, 87MJTIM said:

Now that I have fixed and exhaust manifold leak, I hope the mileage will improve to ~20.  I have been running 14 mpg.  The REM was telling me that I was running in open loop with LT fuel trims at 166.

 

I now run in closed loop and LTFT now running 114 (and dropping).

I believe mine has an exhaust leak at the manifold too. Please keep us updated as to what you end up getting with it fixed.