05 Tacoma and Poor Gas Mileage

im thinking you might need to change the O2 sensor?

Thanks, I'll give it a try.

05 mileage drop

i just noticed a similar mileage drop of about 20% 2 months ago.
was getting 20-21mpg w. mixed city/hiway steady right from new, now its 16-17mpg.
only 23k miles on my 05. i've been running 87 octane , so i filled with 91 last time...made a very slight improvement, but not back to where it the mpg was. i changed tires, but the new goodyear fortera triple tread assurance are the exact same size as the oem dunlop r17's so that hasn't changed my odometer reading. havent changed plugs yet, but i have it regularly dealer serviced. mostly just me as a passenger, and no load in the back except my leer canopy.

i don't notice any performance change, my driving pattern is the same, my foot didnt get heavier, so something is going on. i'll be asking the dealer to address it next time in.

You said the tires are new...what are they inflated to? Try running them high, like 38-40 psi.

Does your gas have a different winter formula where you are? It does here and my milage is down also.

^ He's from So Cal, I'm pretty sure they have the same gasoline formula all year round just like we do here in Vegas. To the OP, have your driving habits changed at all?

the new tires might be the same size but they may be heavier.

I think the first step is to decided if it was an abrupt change, or an on going slower type of change in mileage.

In other words, did you notice it all f the sudden? Or did it take several months before it got to this point.

If it's a sudden thing, you have to see if there were any changes at all made to your vehicle around the same time. Did you put your new tires on? Did you change your air filter? Start using a different grade/different station fo gas? Did your check engine light come on?

If it was a slower process, maybe something is failing or needs to be cleaned. A catalytic convertor is collapsing? An o2 sensor? IAT sensor needs cleaning?

There are alot of possibilities so the best thing to do is to try to narrow the field down as much as possible then start from there.

nope so cal uses a different winter version as well. Happens every winter.