Odometer/MPG/tires question?

So, I'm sure this has been addressed somewhere at some point, but I can't find it in the search function.

I have an '05 reg cab Tacoma, 73k miles. Since I first bought it (new) in 2005, I have had 215/70/15's on it, and my speedometer was normally about 5 miles faster than my actual mileage. Putting 225/70/15's completely fixed my issues with the speedometer.

However, on the 900 mile trip home from Kentucky, I had a lot of time to do some thinking. If my speedometer has been off 5 miles an hour (follow me on this), that means that my odometer has been putting 1.12 miles for every "real" mile driven. Which means that in actuality, my odometer should be reading something around 65k/66k.

I also bought the 100k/10yr mile warranty on my truck...as it gets older, I'm pretty sure that I'm going to hit 100k before it hits 10yrs. Is this just bad luck on my part, or is there some way that I can have the mileage fixed to what it should be? Is this some sort of conspiracy by toyota or the dealerships to screw consumers out of their warranties, or something like that?

Also, my MPG have dropped from what I thought was 23mpg hwy to about 20-21. Not that I can do anything about that, but my window sticker (which I still have) says that I should be getting 23hwy.

Any help would be appreciated.

 

sticker mileage is just a testing average, below the big number you'll see the real range like 18-22 for an average of 20 just example of numbers.
a lot of factors affect mpg, including tires, bigger tires mostlikely more weight, more rotational weight, as well as different tires have different rolling resistance that affect mpg slightly...not to mention air filters/spark plugs condition, etc. etc.

 

IIRC most folks have found that the "error" in the speedo is not a linear 5 mph but a scale (like 5% off). So less than 1 mph @ 10 mph about 2.5 mph at 50 mph and so on. And that the error was in the dial type gauge, NOT in the computer.
So everything has been calculated correctly...just displayed poorly.

As far as them screwing you on your warranty - No. Most companies will still support your warranty past that 100K mark for a little while...and if the distances are being tracked correctly- Then nothing lost.

Your truck is 5 years old- When is the last time the spark plugs were changed? air filter cleaned or replaced? Tires can hurt mpgs...altho going 10mm wider does not seem like enuf to lose 2 mpg....I have no idea how to do that math...so maybe it is right.

 

I was going a little faster than normal anyways. I'm sure there were a number of factors contributing to the lower mileage. Also, good to know that my mileage is accurate. I replaced my air filter before we drove up to KY so it's only been a few weeks. Will look into replacing the spark plugs, prob when I get the brakes checked next week or so. not sure when I last had that done. FWIW, anyone that's only had 215's should try 225's - bumpy roads are still bumpy, but MAN when there's smooth road is it ever smooth.

Thanks Brunes and Eurosport, appreciate the information and clearing up some confusion I had.

 

when i put 265/70/17 's on my truck the speedo is now spot on according to my gps...

 

The speedometer and odometer are completely independent of each other. Your odometer is calibrated to factory tire size, while the speedometer can be off up to (pulling a number out of the sky) 5%. There are a few threads on here about this.

My speedometer is spot on with 285/70/r17's. My odometer reads 6.6% slower. So when my trip meter shows I have gone 100 miles, I have really gone 106.6 miles. I have done a few comparisons already. The next time you take a trip, print and follow the route on Google maps, then compared mileage traveled to your odometer reading. and the miles estimated by google. It is real obvious the longer the road trip. This can even be done with a GPS.