Worsening MPG - 1994 FZJ (1 Viewer)

[Runtble]

When I first got my cruiser a few years ago, it got incredible fuel economy, 16-17MPG freeway. During the past 2 years, it's steadily decreased, now hovering around 11.5 around town and 12 on the freeway.

During this time I have done the following to try to address:

• EGT Disable (not removed)
• Plugs & Distributor (not wires)
• O2 sensors (factory)
• PAIR system removal
• O2 relocation (to PAIR ports)
• Fuel Filter
• OEM Air Filter
• Intake Hose Replacement
• Throttle Body Cleaning
• Coolant sys flush
• Fan clutch mod

All of these have helped power, idle, running temps, etc, but no impact to economy.

What should my next steps be?

 

[MickeyB]

I have a 94 as well with same mods. Following…Also what size are your tires ?

 

[bhsdriller]

Have you added all the stuff to it (weight) and the tent over that time?

 

[sogafarm]

11-12 is normal for an 80 with lift, larger tires, roof rack. etc. I'm wondering how you got 16-17mpg to start with. What octane do you usually use? I get 13 mpg on my stock rig of the same year as yours and the engine runs great.

 

[Runtble]

Have you added all the stuff to it (weight) and the tent over that time?

Yes and No... I got 16-17 MPG on the freeway after the lift and tires, but before the rack and tent. However, I regularly remove the rack and tent when they're not being used, and the mileage stays in the 12 range.

I have a 94 as well with same mods. Following…Also what size are your tires ?

285/75/16R

 

[Runtble]

11-12 is normal for an 80 with lift, larger tires, roof rack. etc. I'm wondering how you got 16-17mpg to start with. What octane do you usually use? I get 13 mpg on my stock rig of the same year as yours and the engine runs great.

That's one of the frustrating things... If I hadn't achieved it at the beginning, I wouldn't be upset about the mileage now. But instead, I had something special and it was taken from me!

I usually run 85 octane and prefer costco or chevron gas.

 

[sogafarm]

That's one of the frustrating things... If I hadn't achieved it at the beginning, I wouldn't be upset about the mileage now. But instead, I had something special and it was taken from me!

I usually run 85 octane and prefer costco or chevron gas.

Was your tire pressure higher? I bought an old fj60 years ago sight unseen and drove it two days back home. I got 17 mpg and was amazed until I checked the tire pressure, they were at a shocking 90psi. I lowered them back down to normal psi and the mpg's went back to normal.

 

[leonard_nemoy]

If all the emissions mods you listed helped with power like you said than it would seem normal to me that your fuel efficiency would have dropped.

More power means more fuel used....

I did a couple engine oil flushes on my rig and my mpg's went from 12 to 13. It can help a little to get all the sludge out of the motor.

 

[manofthewoods]

When I first got my cruiser a few years ago, it got incredible fuel economy, 16-17MPG freeway. During the past 2 years, it's steadily decreased, now hovering around 11.5 around town and 12 on the freeway.

During this time I have done the following to try to address:

• EGT Disable (not removed)
• Plugs & Distributor (not wires)
• O2 sensors (factory)
• PAIR system removal
• O2 relocation (to PAIR ports)
• Fuel Filter
• OEM Air Filter
• Intake Hose Replacement
• Throttle Body Cleaning
• Coolant sys flush
• Fan clutch mod

All of these have helped power, idle, running temps, etc, but no impact to economy.

What should my next steps be?

View attachment 2842128

I'm crying with you brother.
I just did a major/complete rebuild on mine. Mileage is 11ish (and I mean ISH).
Ran good before, runs great now.
Tires went from stock size Michelin, to 285/75 KO2.
changing out break in oil (conventional 10w-30) to full synthetic this weekend. Hoping for a break in "miracle" or, gotta go get me an oil well.

 

[zapatius]

16/17 is an anomaly....11/12 is not. Unfortunately, you'll never regain that mileage. Unless you gut the interior, ditch all exterior accessories and go back to stock tires.

 

[BILT4ME]

1) Are you adjusting your mileage based on the odometer change as well? Going to 285/75-16 tires will cause a 5% DECREASE in mileage recorded, so your actual MPG is better than it may appear.

2) The larger tires cause an increased torque load on the truck and it will reduce gas mileage because of the additional requirements.

3) Larger tires also weigh more, so the rotating mass is more than the stock ones and it can be 30% heavier depending on the tire brand and type.

4) Changing the EGR equipment may affect the mileage.

5) 85 octane? Maybe consider trying a higher octane, as there are better burn characteristics in a higher octane fuel. I always run a minimum of 89 octane. Run non-ethanol if you can find it.

 

[Marco Lau]

so you get 5mpg better than factory claimed number?

 

[BILT4ME]

so you get 5mpg better than factory claimed number?

When my 96 1FZ-FE was at factory height and had the factory sized tires on it and I didn't carry 600+ LB of tools, I got 15-16 MPG all the time.

I now average 11.5 (correctly adjusted) each year, documented for years.

 

[Runtble]

1) Are you adjusting your mileage based on the odometer change as well? Going to 285/75-16 tires will cause a 5% DECREASE in mileage recorded, so your actual MPG is better than it may appear.

2) The larger tires cause an increased torque load on the truck and it will reduce gas mileage because of the additional requirements.

3) Larger tires also weigh more, so the rotating mass is more than the stock ones and it can be 30% heavier depending on the tire brand and type.

4) Changing the EGR equipment may affect the mileage.

5) 85 octane? Maybe consider trying a higher octane, as there are better burn characteristics in a higher octane fuel. I always run a minimum of 89 octane. Run non-ethanol if you can find it.

If I factor in the tires, it comes closer 13. The 16-17 was after the larger tires.

I'll try running higher octane, it might make a difference at this altitude.

 

[zapatius]

When my 96 1FZ-FE was at factory height and had the factory sized tires on it and I didn't carry 600+ LB of tools, I got 15-16 MPG all the time.

I now average 11.5 (correctly adjusted) each year, documented for years

I carry a lot more than I did when mine was new now too. Lots of trail spares - fusible links, EFI relay, head, master gasket set, spare tires at nearly 100 pounds each, 1/2, 3/8 and 1/4 impact wrenches and a full socket set for each.....it just never ends.

The only thing I am kidding about is the head. But I do now have a spare in my garage. And I don't carry a full master gasket set, just like 1/2 of one.

 

[Marco Lau]

When my 96 1FZ-FE was at factory height and had the factory sized tires on it and I didn't carry 600+ LB of tools, I got 15-16 MPG all the time.

I now average 11.5 (correctly adjusted) each year, documented for years.

I get around 10-11 on avg. on 37s, bumpers, sliders, winch, fridge, tons of tools. spare parts. recovery tools and a heavy foot.

 

[leonard_nemoy]

I get around 10-11 on avg. on 37s, bumpers, sliders, winch, fridge, tons of tools. spare parts. recovery tools and a heavy foot.

Your comparing apples to oranges here, unless you ditched the 3fe...

Surprisingly enough my 91 never got below 12mpg and it would commonly average 15-16mpg on long highway trips, but I mean real highway not interstate driving. My 91 loved cruising 55-60 mph.

 

[Dusten]

If I factor in the tires, it comes closer 13. The 16-17 was after the larger tires.

I'll try running higher octane, it might make a difference at this altitude.

Octane has nothing to do with burn efficiency. A higher octane fuel resists early ignition. In theory you want to run the lowest octane you're tuned for. Even if somehow you managed a small gain, it's likely you won't offset the cost of the higher octane rating.

 

[LongDuck]

Posted as commentary,

 

[Marco Lau]

Your comparing apples to oranges here, unless you ditched the 3fe...

Your comparing apples to oranges here, unless you ditched the 3fe...

Surprisingly enough my 91 never got below 12mpg and it would commonly average 15-16mpg on long highway trips, but I mean real highway not interstate driving. My 91 loved cruising 55-60 mph.

No way I would ditch the 3FE for the 1FZ...but if i do swap, it will be a V8 so i can spin the 40s. Otherwise, the 3FE is just as good for my application.