Bad gas mileage

2015 Tacoma dbl cab 4cyl is getting 15 mpg city and 15.5 mpg hwy.
Tires are 265/70R17 instead of 245/75R16. Also she's very slow off the line and when running the highway with cruise control and we climb any bridge she drops a gear. anyone got any ideas besides driving it off a cliff?

 

How are you calculating your mileage?

 

By changing your tire size your changing the ratio of your gearing. You'll have to regear it for the new tires, or go back to the stock tires if you want to get better MPG's. Though you're still likely to lose some mpg's to bigger tire because they are also heavier then the stock tires are. That's especially tuff on a 4banger.

 

It's not too surprising. Going from 16" wheels w/245 to 17s w/ 265 you've gone to a heavier wheel tire combination. In addition, there is is a slight diameter difference between the two, so you're getting slightly better mileage than you can think. I went from steel wheels with 245/75-16s to alloy TRD OR wheels with 265/70-16s last spring and lost 2 mpg. I bought my 2013 AC new and it's always downshifted on slight grades. It's the byproduct of a small engine and heavy truck. And your double cab is even heavier than my access cab, so the mileage is going to be even worse.

 

Make sure when you're calculating your mileage you take into consideration the ratio of difference between tire sizes. I went up to a 285/75 which is a 12% difference from stock. so when you divide mileage by gallons consumed I multiple by 1.12 and that's my actual mileage.

Mileage still dropped for me, but not that much. I'm getting high 17s combined and have seen just over 20 mpg on long hauls

 

I am considering dropping down to the factory size, but I want to stay alloy for the weight factor or the lack there of. thanks for the imput folks,greatly appreciated.

 

Did you put the 17s on the truck, or were they on there when you bought it? One option would be to sell the 17s and then buy a set of 16 factory alloys. When you buy tires, do some research on tire weights. That's the advantage of the factory Dunlops...they're a pretty light tire and that helps with mileage.