what the hey happened to my gas mileage??

[DevinSixtySeven]

00 tundra, roughly 70K miles. was getting 400 miles to a tank, am now getting 300...nothing changed except i moved to ohio from colorado. towed a lot of stuff on the way out here...

have a cracked exhaust manifold (again), and a bad right cv joint. spark plugs are roughly 30K old denso iridiums, still look ok but don't remember how long those electrodes were when they arrived. are these alone enough to cause this huge drop in mileage?

it's not the throttle body, fluids, tires...already checked those. it idles a little rougher than i remember. any ideas? this is driving me nuts.

-sean

[MustangSally]

Originally posted by DeepStealth

... was getting 400 miles to a tank, am now getting 300...nothing changed except i moved to ohio from colorado...

Could be altitude/elevation...

Dayton, Ohio is approximately 740' above sea level, and Boulder, Colorado is around 5,363' above sea level.

I get 300 miles/tank here in Los Angeles at about 125' above sea level, but when visiting my brother in Boulder, Colorado, it is right around 400 miles/tank.

~MS

[chuff]

Altitude would certainly play a role in your mileage. At higher elevation there is less oxegen and the air isn't as dense as it is at sea level. Less air mass and oxegen the engine desn't need as much fuel or octane, so it uses less, but you have less power something like 5 horse for every 1000 feet you go up. I have no clue whether or not you should lose almost 1/4 of your mileage but I would accept this explanation. I live in Iowa, I normally see just a tad over 300 miles per tank, that's if I drive conservatively!!

[DevinSixtySeven]

ok...but i did get 300 to a tank when the truck was bone stock, after a k&n drop-in, new plugs, clean throttle body and new manifolds, i got 400...and that's with 33" x/ts (it was the same before and after the new tires, 400).

i am actually thinking it might be running rich since the left O2 sensor is probably misreading due to the leaking manifold...

-sean