instal rear diff. on a 2wd? and best tire size, for best MPG?

Hi Tacoma owners, I Just bought a 2wd access cab sr5 2009(My first pickup). I got it 2wd because of the fuel economy. Found the wheels too small and the rims ugly and came very low too. I lifted it 2.75inches and got mags with motomaster 265/75 R16 off road tires. My fuel economy went down in a rush. And the front tires are rubbing. Can tire brand affect mpg? What is a good tire size for a good look and good fuel economy (Original 15inches are too small).
I wondered if after all a 4wd would have given me the same mpg as now? Anyways I have the truck and gonna stay with it. I want to go off road.But the truck has no rear lock. Any suggestions or previous experiences? how much would it cost? does it affect MPG? Mine has the LSD, Is it any good off road? what Does it do? Sorry if theres too many questions, I'm new to the forum and happy it exists

 

What is the year of your truck? 2009?

The Load Range of your tire will change the weight, and thus, effect your gas milage.
A passenger (P rated) tire will generally weight significantly less than an E rated LT (light truck) tire.

265/75r16 shouldn't rub even on an unlifted pre-runner. Are you sure you're truck is a prerunner and not a regular 2wd?

15 inch wheels will not work on a prerunner tacoma. The brakes will not clear.

Getting a locking rear differential will not effect gas milage because you will only use it (lock the rear) when you are stuck or think you may get stuck. Driving around the street, the rear will not be locked, and you will get the same MPG you get now.

As far as lockers, you can get an ARB air locker for around $900 USD.

 

Adding a locker won't affect MPG. It acts as an open differential until the locker is engaged.

 

Thanks, and I'm not exactly sure What it is exactly heres a photo of what it looked like when I first got it.http://cloud1.autoweek.com/carshopping/vehicle-images/2010TOY014a_640/2010TOY014a_640_03.png

 

Wheels & tires are unsprung weight i.e. the vehicle is sprung; the tires & wheels are not.

Unsprung weight hurts acceleration and gas-mileage, badly. For acceleration, that unsprung weight must be rotated, which takes energy i.e. power i.e. gas. Even cruising (e.g. for gas-mileage) wheels and tires must be spun.

`don't believe me? Imagine spinning a donut on a pole; now, put a wheel and tire on the pole ... and spin it. Which requires more effort (energy ... gas)? Look at the manufacturer and EPA gas mileage configurations. Which wheel & tire combination shows the greatest gas mileage? ... the smallest!

The less unsprung weight, the better - for acceleration & gas-mileage. Smaller diameter wheels and tires make for faster acceleration and greater gas mileage. Those monster wheels and tires just slow everything down. `sorry; that's just physics.

While we're at it, the greatest aerodynamic drag on a vehicle is the air that gets UNDER it ... and bounces up and down between the ground and the vehicle. That's why race cars are built as low as possible without touching the ground. The higher the truck, the worse the gas-mileage! The more the truck is lifted, the worse the cruising gas-mileage will be.

 

Not a prerunner, 5lug

That's why it was possibly lower than u expected. No biggie, that can be overcome as u already know.

 

Hey man to save time typin.... I've done all of that and get about 24-26 mpgs

32" tires
rear diff 4.10 gears w/ARB air locker