??Can this be true??

I have a 05 prerunner 5spd 2.7 2wd with the access cab, it had a 3" spacer kit from revtek and 285/75/16 BFG Mud and was getting 15.7mpg on first tank not really worried about gas driving. So I started driving more gas conscious and only got 16.1 next tank. Thinking it was the meats I bought some 265/74/16 Hankooks and switched from the revtek to 5100s all the way around and kept shifts @ 2500, but only yielded 16.9mpg! Have all mobile1 synthetic fluids in motor, trans, and dif, NGK plugs and not to mention I just installed a new air filter that is strongly recommended on this site. I'm not expecting 35mpg like my Yaris did, but what the deal with my bad mpg

 

hmm idk... you should be getting around 20

 

That is what I was going for when I bought it, I know there was this big deal about the thermostat on the FJs causing bad MPG because it stayed in the open position never letting the motor reach operating temp causing RPMs to constantly stay higher and the comp telling the injectors it needed more fuel. So maybe need new thermostat

 

okay heres how to check that....


when the truck is completely cold, take the radiator cap off, start it, then run around to look at the fluid inside of the radiator, if it starts flowing instantly its stuck open, if it takes about 2-5 min its fine

 

Did you correct the mileage for the larger tires?

 

great DIY diagnostic..Thanks!

 

Nope I did not, do you have a DIY diagnostic for that

 

(old tire diameter-new tire diameter)/old tire diameter.

That gives you a correction factor then multiply that by your trip milage to get your actual

 

Use the tire calculator on the site , it's easy

 

285/265 = 1.08 x 287= 309.96/17= 18.23MPG

I think that is correct, I feel a little better now, but am I still off beat of MPGs for my application

 

nope thats about right. better than i get in my 4 cyl with 31s haha

 

285 and 265 are the width of the tire not the diameter

Trust me , use the site's tire calculator , there's a link on the home page

 

Oh shit your right!

So should I calculate off of the factory tire diameter (since that is what the comp is calculating miles off of) vs new diameter?

 

Go to the tire calculator , input the two tire sizes you are comparing , use the % adjustment between the two sizes to correct your mileage

 

Ok here we go...

Formula 1 based off stock tire vs current:

1.18 x 287= 338.66/17= 19.92MPG

Formula 2 based off BFG vs current:

-1.18 x 287= -338.66/17= -19.92MPG

I'm going to say its prob Formula 1 which means the comp reads miles based on stock tire size, which makes sense if it does this off of RPMs as well, so I am currently shifting at a much lower RPM?

 

The "old tire diameter" number should be your stock tires, that is what the speedo and odometer are calibrated to.

 

Correct