I used my sisters gps system in my car yesterday. I reset my trip meter and the gps meter and then did my daily trips that I need to make. My odo was 1/10 off compared to the gps.

So when I got home i recalcuated some of my old gasoline receipts. My mpg whent up amazingly.



xxxGALLONS xxxxTANKxxxxxMPG AVERAGExxxxxre-adjust x .10 new mpg
xxxx9.542 xxxx316.5 xxxx33.2xxxxxxxxxxxxxxxxxxx 36.48



316.5 *.10=31.65
316.5+31.65=348.15
348.15/9.542=36.48


Am i correct in my math? I sure hope im correct for once

 

The better question is, what is the error in the GPS? I'm guessing it's + or - some value which may negate your potential efficiency.

 

you make a good point

if not ill stay with my 33.2 - which iwas very happy with

 

do you have aftermarket wheels and tires?the tire size can throw it off

 

i run stock wheels and tires.Nothing changed

 

i got the same issue, thought it was the gps, but took my wifes car and the gps was dead on with it and a little off with my xb... at normal speeds, 65 and below, its pretty close, but on the long straight aways, go a lil faster and you can see the difference.

 

thats funny, my odometer reset itself recently, lol. it said i had 0 miles on the car, then as i was driving it got to 3 miles and completely stopped counting. i was seriously thinking about selling it, lmao

 

We drove from WA to TN and the GPS vs. Odometer had a 60 mile or so descrepency. I think the GPS showed more miles... I'd have to ask my husband, he'd remember.

My GPS can get me within a foot of a Geocache, odd to thing the odometer is off.

 

Based on comparing the odo to highway mile markers, my odo's about 3% short. I'm running stock wheels+tires. 10% sounds awfully far off - what wheels and tires are you running?

 

I'm running stock wheels+tires

 

several people have noticed the odometer is 3-4% slow and nobody knows why. Speedometer is 4-5% fast, as it is on many other cars too.

 

i use microsoft maps for work on a dialy basis, my xb is also a tad off, at first i thought it was the program but my boss' subaru was right on... then i thought it was my after market wheels, but my stock ones are the same... do you think theres an issue in converting kilometers to miles? im not sure ive heard of the issue in many other cars... not that it bothers me at all

 

xBs come with the speedometer reading about 3% high. This has been noted my many people using many different methods, using stock rubber.

 

I've often wondered if the odo is off by about 3% because the USDM tire (15/185/60) is about 3% smaller than the JDM tire (15/185/65).

I'm not sure about that, but the service manual for the xB specifies that the speedometer be calibrated so that it reads about 3% too fast.

 

Ding Ding Ding. We have a winner. You are exactly right. The spedo is calibrated for the bB which comes with 185/65/15's. That is why it reads 3% higher. Just add 3% to your miles when doing MPGs and you will be right on.

 

IF THATS TRUE- WHAT IS MPG GIVEN in THE EXAMPLE BELOW?
i


xxxGALLONS xxxxTANKxxxxxMPG AVERAGExxxxxre-adjust x .10 new mpg
xxxx9.542 xxxx316.5 xxxx33.2xxxxxxxxxxxxxxxxxxx 36.48



I DONT WANT TO CHEAT TO GET BETTER MPG-

 

it should be .03 mulitiplied correct

 

You take the travelled miles and add 3% before you calculate the mileage.

316.5+3%=325.99 then you divide the mileage by the gallons 325.99 divided by 9.542=34.164 MPGs

 

ty i realized i put down 10% originally. I'm very pleased with my box - always have been - always will



thank you all for you help

 

Of if you want a quicker, easier calculation, just multiply your calculated mileage by 1.03.

33.2 * 1.03 = 34.196. Call it 34.2.

If you're less fussy, you can always just add 1 mpg, since 3% of 33.3 is 1.

Of course, the farther away you get from 33.3 mpg, the farther away you get from your easy fudge factor of 1.