2005 Toyota Tundra gas mileage question

2005 tundra access cab sr5. Recently started getting bad gas mileage. Getting about 100 miles on half tank of gas. What should I have Toyota look at first? Should I have Toyota perform MOC fuel induction service? It has approx 65,000 miles.

Well, first of all you are not actually checking your fuel usage. You are just guessing and your vehicle is past the age of going a dealer for repairs.
Until you check your mileage the proper way don’t pay for anything.

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You shouldn’t suggest anything to them. You should only tell them you feel the mpg has taken a drastic dive. Otherwise they may only do what you say regardless of if it will fix the problem.
I agree that checking the mileage properly is a good idea. Although on my Camry’s I know I should get between 220-250 miles on a half tank. If I suddenly get only 100 miles I know something’s wrong even with out the exact calculations.

Start checking your gas mileage by taking the miles you got on the tank and dividing it by the amount needed to fill up the tank; hopefully, you can remember the mpg’s sometime in the past and compare; or if nothing else, maybe you can find the EPA ratings. If there’s not a big difference, you’re done.

If there is a big difference - and to me a big difference is 20% for a single tank (16 miles per gallon, when you have been getting 20, for example) - think about how you’re driving and the kind of trips you took. Winter time lowers mine 1-3 mpg. Strictly interstate driving increases mine 4-7 mpg.

See if there’s any preventive maintenance things that are behind. One of which I’m frequently guilty is the engine air filter. Another that is frequently missed is tire pressure. Take care of the stuff you should have been doing all along before you get into the fancier and probably more expensive stuff.

Once you’ve done all that and you’ve gotten several tanks of gas that all have bad gas mileage, then consider the fancier stuff.

As others have said, get a real measurement first. If it really did dive, one reasonable possibility is a thermostat that’s stuck open.

Not nearly accurate enough method to tell what (if any) kind of hit in mileage your experiencing.

What kind of mileage was it getting previously, and what was your methodology of determining it?

What is the drivetrain combination? (Engine, transmission, 2WD/4WD, etc.)

The reason the using X miles per half tank of gas method is flawed is 1. Just eyeballing it isn’t very accurate, and 2. fuel gauges aren’t necessarily linear. You should track your mileage using the pen and paper method ( number of gallons it takes to fill up divided into the total number of miles you traveled on that tank), using the same gas pump each time preferably, and then averaging that over 3 fill ups or so.

Studies have shown that dirty air filters have an extremely minor effect on fuel economy

I’m talking about dirty air filters . . . NOT ones that are plugged solid or an air box full of acorns


I’m glad to know that! It seems to be one of those things that I’ll get around to doing but find excuses to put off for another day.

Back when engines had carburetors, a dirty air filter could reduce your mpg by acting as a choke, but in modern EFI cars, the mass air flow sensor and the closed loop oxygen sensors will compensate and adjust the amount of fuel injected in response to less air flow, just like they do for high altitude driving.

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Unless you have money to burn, skip the induction service. Find what the actual problem is and work from there. If it makes you feel better, throw some Techron in the gas tank. I’ve had that successfully improve rough idling in a car that had high mileage.

I love the trick they played with that document - not putting in an executive summary, so you’d have to read all the paper. Well, ha ha, I fooled them - I went straight to the conclusion section (it’s on p. 37 if any of you would like to do the same).

I thought that measuring the intake air flow would reduce the gas mileage impacts of a clogged air filter.

Thanks for sharing.