My relatively new-to-me Excursion has what everyone on here affectionately calls the "Lie-O-Meter". My old F250 didn't. So I've been watching it over the last few months that I've owned the Ex to verify accuracy.

I've always been surprised by how off people say there numbers are. It didn't make sense that it would be that far off for the entire model range.

Cutting to the punch line - My testing so far shows that the Lie-O-Meter is pretty accurate.


The day I bought my Ex, the Average MPG showed 13.3. The truck was running on some 285/75/16 all-terrain tires - Falken WildPeak in the rear, Bridgestone in the front. Under my driving style, the Average slowly started to increase. So I decided to reset the Average MPG and do a couple of fill-ups and compare. I changed the fuel filter and oil to T6 and that was it as far as maintenance went. Over a couple of cycles of mixed driving to/from work, towing an open trailer w/ car etc I netted an average in the 14s. The best was 14.2 MPG and it stayed there for a couple of cycles.

I hated how the 285s affected gearing and speed. The gearing change forced me to drive a bit slower to maintain the RPMs under 2,000. Pretty annoying on a long 150 mile trip... I also hated how the all-terrain tires felt on the street. I could feel the knobbies through the steering wheel in corners and it annoyed me - a lot. Mind you that I race cars for fun so I'm pretty sensitive to things like tires and steering feel. YMMV.

I wound up replacing those tires with some stock sized (265/75/16) Michelin LTX / MS2 highway tires - which I'm really liking btw. Avg MPG immediately started increasing to 15. Hmmm.... Time for a reset.

Reset the Avg MPG and continued driving the Ex in my usual routine and ran a couple of tank fill-ups. I'm up to 16.6 AVERAGE MPG now on the overhead console and it matches to my hand calculations.


I think the thing to keep in mind when referring to the Avg MPG display is that is an AVERAGE. If you haven't reset it in a while, I can see how it could be inaccurate b/c it is averaging all values since the last time it was reset - that could have been 100k miles ago or it could have been 10 miles ago. If it was a long time ago, then the law of averages says that your most recent mileage won't really influence the math to calculate the average.


Hope someone finds this useful...

 

One thing you didn't take into consideration with the 285's (at least it was not mentioned in your post), is the fact that at the same 2,000 RPM level, you were actually going 2-3 mph faster on 285's than you will with stock sized 265's. In other words, even though you thought you were going slower on the 285's, you were not because the speedometer had not been recalibrated for the larger diameter tires... the speedo was simply UNDER-reporting your actual speed.. This also would reduce any mpg difference's you are seeing with the 165's because you actually had more miles than you calculated with your 285-related mileage calcs.

None of the above addresses any issues of how the 285's feel on the road, so I have no comment about that personal preference issue.

Also, and I know you are already aware, the 285's hurt your mileage from two different standpoints... tire weight, and reduced aerodynamics (due to wider tire face and higher vehicle stance).

I've seen a few other people find their overhead display to match their own driving style fairly well, but it is not a common thing at all.

 

Learn something new everyday. Never thought about that. Thanks.


Yep, I"m aware of that. Also the all-terrain tire tread has more rolling resistance than highway tire tread.

 

My overhead was pretty accurate... til I got a chip then it shows higher than actual.

 

I just finished a trip, in which 290 miles of it were figured into the mpg. Flat steady interstate, 70-75, overhead reset at fill up, hand calculated 18.2, meter said 25.2.
Just saying it is off. A lot.
I haven't tried back to back tests, but it SEEMS to be off more on 80e vs stock. Just an observation.

 

When my truck was stock, the lie-o-meter was dead on with hand calculations. That changed when I added a chip, now its dead wrong.

 

Thats the thing..They are close to accurate until a chip/tuner is added..

 

I was pretty close with my chip on stock injectors, but my new injectors make the liedometer optimistic by 8 MPG.

 

So, does anybody know where the meter gets it's information? What are the parameters that it figures mileage from?

 

I can guess that it's based on the FIPW, ICP, RPM and MPH, then it's up to the nozzles and the rest of the system to respond to the theoretical model. I suspect the liedometer is telling you what a new truck should get with all the criteria above, and the difference exposes inefficiencies with a stock system. Once we mod, the liedometer is nothing more than a night light. I do use it to see if I get increases/decreases in the readings after another mod/repair.

 

I get the impression that I am the only one with a stock truck here.

 

Nope. My 2003 Excursion is pretty much bone stock as well except for just a few very minor mods (harpoon/hutch, 6637, HPX, and AIH delete).