Sudden Poor Gas Mileage...

Hello good people of TacomaWorld. On a drive home for the Holidays, I drove from Grand Junction, CO to Boulder, CO to Dallas, TX, and I couldn't help but notice that my gas mileage very suddenly got worse. I'm the guy who sets his trip meter every fill up and scrutinizes his gas mileage (although I don't drive like a grandma). I usually get 21mpg in CO, and about 19.5mpg in TX, but recently I've been getting like 15mpg. I was a little overdue for an oil change, so I changed my oil with Castrol Edge 5W-30 and an STP filter and I haven't noticed a change yet

 

Elevation change

 

air filter clean? throttle body clean? tire pressures not too low? were you carrying a lot of extra weight for the trip?

 

Payload and tire pressure? Warm up the truck because its cold outside?

 

Winter gas?
Cold weather?
Mine drops a couple MPG's during Winter months.

 

First of all @ChadsPride thanks for your unwavering support.

There was a fair amount of additional weight on the trip (myself and my friend, our luggage, two bicycles) but not enough to warrant that dramatic of a change in MPG. I've contemplated it being the air filter. Maybe i can disconnect the battery and let the ECU reset?

 

No problem at all ​

 

I can check the tires but I don't think they're the issue. I'm due for a rotation anyway. What's strange is that I don't notice a power loss to complement the poor MPG, which I know is purely off my judgement of how the truck feels, but it leads me to believe that I'm running rich and not bearing a bunch of extra friction, which is a good sign. It's also been 20 degree temps in Dallas the last few days, and I still get steam out of my exhaust when my truck is warm under acceleration. I don't know if that's a sign of running rich or not

 

Your truck is telling you it doesnt like Dallas. Hell, i live in Ft Worth and cant stand going to Dallas!

 

weight is HUGE.

Lower temps, winter gas..... 15 sounds rightish..... i have been gettin 16.5 lately and it sucks.

 

Probably the winter blend gas and the extra weight

 

usually thats just the temperature difference. If its actually steam from the engine you have problems...ie head gasket. I forget what year they quit using a replaceable fuel filter but if its one you can replace I'd check that.

 

also no CEL?

 

Mine has been down ever since the winter gas came out. I bet in the spring your mileage will go back to normal, but it’s not a bad idea to check some of the above mentioned items. Engines also run richer in the cold.

 

I'd guess you picked up some bad gas somewhere (not from Mexican food) and the ECU is confused. Let it be. Drive the tank nearly empty. The problem will likely solve itself over the course of the next tank.

 

As mentioned by others above, I always lose 2 mpg with the switch to winter blend fuel.

 

I have yet to calculate my gas mileage

EDIT: ever ​

 

Not the worst policy. If you go looking for problems, you'll find them.

 

He means he cant operate a calculator.

 

He's newly married. His hands are busy