My rig - 2009 Tacoma 4x4, 67,000 miles.
Hi, after racking my brain for the last 6 months where I have seen my mpg drop from about 19-20 highway to about 11-12 highway and doing everything I could find recommended on this forum including maintaining tire pressure, oil changes (synthetic), changing my spark plugs, changing the air filter (and in-cabin filter too), cleaning the MAF, running 2 cans of Seafoam, a can of Duralube injector cleaner, buying non-ethanol gas, non-winterblend gas, only running premium for a few tanks, etc. I couldn't figure out why I was getting such bad mileage and gave up for the last month.
I drive a lot. Like, all year round, all seasons. This truck sat virtually unused for 2 years while I had a company truck so all those miles were fairly recent and I monitor my gas mileage constantly, virtually every tank.
Today I decided to drive without using my air conditioner since I was mostly in the cooler mountains and bam, I was up to 20mpg again. Drove 390 miles today total so got a pretty good gauge.
First question, is it normal to have the gas mileage drop to 11mpg when using the A/C on a 2nd gen Tacoma? It seems incredibly excessive to me. Seems like it was dropping maybe 4-5mpg max (usually less) for most the time I owned the truck, not 10mpg.
Second question: I'm still getting like 11-12 (sometimes as high as 14) in the winter when I'm not using A/C at all. Since the in-cabin air filter is new (and I keep it clean), why is the heater causing my gas mileage to go down almost as much as the A/C does?
Thanks for the great resource! I've been lurking the threads for years, anytime I google a question I usually end up here. Can't find an answer to this one though.