Just back from a 7250mi trip from NW FL, to west coast, and back, mainly on I-40, with enough "blue highways" to keep it interesting. Checked a measured mile in Eureka, CA a couple of times and found the odometer to under-read a bit, but difficult to quantify, so checked a 50mi stretch of I-40 in W. Nevada, mostly arrow-straight, and found the odo under-read by 1.6mi, for a 3.2% error.

With this correction my calculated total FE rose from 23.9 to 24.7mpg. Westbound, our FE was 24.1 corrected, and eastbound 25.7, with westerly winds probably accounting for the difference.

Pete Berry

 

Has anyone else seen this under-reporting on the ODO? I did on a trip from CO to CA ... noticed becasue I filled up within a mile of the NV/UT state line on the way East - mile markers start at 0 at the UT state line and my ODO was off significantly by the time I hit Salt Lake City (long, boring straight shot). I can't remember the % it was off but it concerned me enough to mention it to the dealer... of course they took it to their "measured mile" and didn't find any errors but I believe you'd have to travel several miles before even a 5-6% error would show.....

 

Forgot to mention that I have the Integrity tires, inflated to 36 psi. What are yours, Shiloh?

A 3.2% odometer error ain't that large, but it means under-reading FE by 0.8 mpg at a calculated 25 mpg - which translates to a "free" 320 mi tank every 10,000 miles indicated on the odo.

Pete

 

The OEM Goodyear Integrity has a diameter of 28.4” which is 1% smaller than the OEM Michelin Energy LX4 which has a diameter of 28.7”. This will make the calculated fuel mileage "appear" to be 1% less with the Michelin tires just due to the odometer under-reporting error.



New tires have about 10/32 of tire tread while fully worn tires have a minimum of 3/32”. Fully worn tires will be 1.5% smaller in diameter than new tires and will make fuel mileage appear to be 1.5% better due to the odometer over-reporting error.



Toyota must take into account the different OEM tires the Highlander uses along with the expected tire wear when calibrating the odometer. Changing the tire pressure and load will also affect to a degree, the revolutions per mile that a tire will turn.



It is interesting that the MPG display on My Highlander is off by 3.7% over 6 full tanks of gas when compared to the MPG calculation using gallons and odometer miles. The MPG display is a bit optimistic by about 1 MPG. Maybe some of this can be explained by the diameter of my Michelin tires.



I will check my odometer against my GPS unit which probably is much more accurate than the odometer for recording mileage driven.

 

I have the michelin tires.

 

With odometer correction, the MPG display on my standard HiHy is a little less than 2% optimistic - 29.1 vs 28.6 actual on the last tank.

I'd believe the GPS only on a straght section of road at a slow, constant speed, as integrating the variables of speed, direction, position, and satellite signal when they are constantly varying at road speeds would probably prove a great challenge to a consumer unit that updates once a second.

Pete