wondering why i get 13 mpg?

Probably drive like you are on COPS.

 

So I have the 4 cylinder and 70 miles an hour in 5th gear has the rpm at about 2700 ( rough guess. Is this bad should it be lower?

 

2005 DCSB, 285/75r16 (33 x 11.50) Mickey Thompson Mtz. Perfect air pressure & I usually drive the posted speed limit. I get on average 260 - 275 a tank.

 

I get 17 miles on highway 6" lift and 35 toyo mt. I drive like a grandma and never take it over 2k

 

I get 300-320 miles out of a tank and drive mostly in the city. I did a few mods that allows for this. I took out coal filter, put in a K and N drop in filter, made my hood scoop functional and drilled holes in the top and sides of my air box to increase the amount of cool air that enters the motor. It now sounds better and accelerates better as well

 

Pretty sure you want warm air for better mileage and cool air for performance, you can't have the best of both worlds. I could be wrong though, but some of the "eco guys" on custom were moving their intake closer to their engine to suck in warmer air if I'm not mistaken.

 

im thinking the colder the air the better for mpgs. yes, colder air will make you use more fuel when going WOT due to the fact of making more power at WOT, but driving normal speeds less than WOT, you should need less throttle angle to acheive the same power as in the hot environment

although cold starts and warming the engine up to operating temperature will eat more gas so in that respect yes warmer is better.

 

The theory goes...
-warm air means greater throttle opening for the same airflow, thus lower pumping losses
-warm air tends to vaporize fuel a little better
-warm air intake lets the engine warm up marginally faster

You don't really see a difference in mileage unless it's quite cold out when the engine computer won't pull timing from excessively hot air. Once the taco takes timing it doesn't want to give it back.

Now on a MAP system or a lower compression engine it's a different story. A lot of Saturn folk like to get their IATs up to 160+ and start aiming for mileage in the 50s.

 

2002 3.4 V6, 6" of lift 33x12.5x20 tires, and my foot's solid lead. 14mpg

 

$2.99 purchased in San Diego on Saturday 2/21/12

 

I get the same mileage as OP, about 250 a tank. I have a 3" lift with 265/75/16's. When I had 285's, I swear I was getting 350 a tank. 100 miles is a big difference. I change my oil and recently changed my plugs, but I still get the same mpg. Could the difference be because I went from D-rated at's (285) to E-rated MT's (265)?