Quick Question: Mileage Expectations

[umr_engnr]

I have a new to me 2000 Ford Explorer with the following specs:

4406 swap
Torsion twist of several inches
1" body lift
Roof Rack
5.0L V8
Rock Sliders and Custom rear bumper with full size spare
33" Pro Comp MT2 tires
3.73 gears

My onboard computer is reporting about 10.4mpg with all around town driving and a single passenger. Last fill up showed about 11.2mpg. On the trip home it got up to about 14mpg doing mostly highway. Does this sound reasonable with all the modifications or should I be looking for a problem?

Tailpipe is clean, doesn't smell rich, fuel trims on scantool don't look excessive.

I am planning on a tuneup (plugs, wires, pcv, etc), but was curious what the consensus is on how much mpg I should expect. Thanks.

 

[Blown]

Larger tires = higher gearing and your odometer is off. Could be about 12% if your rig came with 245/70 16's stock. More if it came with the smaller 15's.

 

[umr_engnr]

Good point about the speedo; however, I did check and the speedo is dead on with GPS, so the previous owner must have had it adjusted.

 

[Blown]

I am not aware of being able to adjust these rigs speedo, at least not easily. It take's a black box not a simple gear swap and it's not cheap.

Anyway, I think it should be getting better mileage, gearing could be lower if everything else is good.

 

[Mbrooks420]

I think your mileage is about right. 33’s are tall for 3.73’s and you are pushing a lot more wind being taller and having the roof rack.

How many miles are on the motor?

 

[Turdle]

Sounds about right. You might fight hard and get 1 MPG more with alignment tricks, remove roof rack wind fairing. Fender flares might also help a bit if the tires stick out past the fenders.

 

[umr_engnr]

I think your mileage is about right. 33’s are tall for 3.73’s and you are pushing a lot more wind being taller and having the roof rack.

How many miles are on the motor?

The motor has 89,600. It feels pretty healthy. Not as powerful as I was expecting with the V8, but that might be due to the 3.73 and 33". I've got a 1989 F350 7.3L diesel with 33" and 4.10s and it isn't necessarily overly peppy either.

I was planning on moving to 4.55 gears eventually, and possibly move to 35s.

 

[umr_engnr]

I live right next to work and maybe put 5000 on a year so the cost of gas isn't a huge concern. I just want to make sure nothing is wrong.

 

[German Engineer]

10.4 MPG is poor, but very possible driving around town, depending on your driving habits, traffic conditions and all that.
14 MPG on a highway is also really poor, but possible as well.

With the current gas prices and not much hope for them going back down a lot anytime soon over time that is going to come pretty costly though.

I suppose the tires you mention you have on there are off road tires? Those types of tires can "eat up" a lot of gas.

I would probably keep an eye on or check the brakes and the parking brake though, just to see if they disengage properly.

It certainly wouldn't hurt to jack it up or put it on a lift and rotate the wheels by hand to see if they move freely or if there's any kind of resistance.

 

[German Engineer]

Oh and another thing: You might also want to check your alignment.

Edit: And another other thing you could check is if the differentials function properly.

 

[Blown]

I got 10 around town with a 351W blown Bronc on 40's at a mile high (If I kept my foot out of it). Just saying. Gearing is dogging your mileage around town and it's got to be hard to keep it in the right gear for best mileage.

 

[umr_engnr]

Larger tires = higher gearing and your odometer is off. Could be about 12% if your rig came with 245/70 16's stock. More if it came with the smaller 15's.

So I double checked this with my scantool, and indeed the computer speed and true speed were off by at least 10%. I took it to Ford today to get it adjusted, but they ran into an ABS limit on how far they could adjust the revs/mile. I started a new thread to discuss:

Explorer Speedo Calibration Limit

 

[Mbrooks420]

So is your gps off as well?

 

[umr_engnr]

I'm not sure why it looked okay the previous time I checked.

The scantool compares GPS vs vehicle computer reported speed. This last time I checked it was obvious they were off. At 20 it was off by 2, at 30 off by 3, at 60 off by 6. Exactly what you would expect from a multiplier being off. It was a linear relationship and not a constant offset.