Another MPG thread - Anyone account for tire size and odometer discrepancies

My speedometer shows 1 mph faster than gps but the miles registered on the odometer show I have driven 96 miles when I acually drove 100 miles.This with factory tires.265-70-16.In order to get correct MPGs I would have to add 4 miles for every 100 miles driven.I have checked this several times.

 

I need to break out the GPS. Because I have stock size 265/70r16 BFG ATs and my speedo reads about 2-3mph faster than my Ultra Gauge speedo does. But as others have mentioned in this thread, I also have heard that the speedo can be off and the odometer still right on. Will have to confirm. As for which to trust most ... odometer, mile markers, or GPS ... I'd take GPS any day.

 

I asked that question once and I can't remember the answer I'll have to dig through old messages to find the answer. I have checked it myself and come to the same conclusion.

 

The speedo gearing or gauge markings could be slightly off. There's no reason if one is accurate the other must be too.

 

Odometer is 100% digital signal to digital display. The Speedometer is a digital signal being sent to an analog gauge. This is where the difference occurs. To be on the safe side Toyota (and most other manufacturers) cover their own ass by making sure the speedo reads faster than you are actually traveling. So when you think you are going 60 MPH, you're actually going 57 MPH. This will keep you from getting speeding tickets. If the speedo said you were traveling at 60, but you were actually going 63, that would be a no-no on Toyota's part.

To summarize: digital signal sent to analog gauge equates to some amount of % error.

 

Someone would sue and the Government would have to do a big investigation if Toyota did not cover their butt.

 

I am running with 265/75-16s for better mileage. Just remember the bigger tires will slow the speedo so watch the school zones. You will be going faster than the speedo reads. School zone tickets in Texas are a Bitch.

 

I'm running 265/70R17 and my speedo is dead on, yours probably is also.

 

I have a similar setup as you and I would do cartwheels if got your stated mileage.

I'm getting 12/13 mpg with the lift and tires. Down from a solid 21 mpg stock.

Not yet regeared.

 

I'm running 275/70/17 and my odometer is in kilometres and I fill up in litres , how can I convert to US MPG and include my % increase for tire size ?

 

The % increase is simply a difference in circumference. Determine what the difference is, convert kilometers to miles, and convert liters to gallons.

 

Good stuff.

 

I get 330 miles on a tank with 285 65s someone figured mileage for me with the odometer adjustment