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Yet another tale of declining gas mileage

We have a 2004 Toyota Matrix. It’s a XR 4wheel drive- automatic. It has 104K miles on it. Runs as good as the day we got except for 1 thing- the mileage has gone from 36 +/- mpg to around 27 mpg. I’ve done all the obvious things- new plugs, proper tire pressure( new tires), Techron additive. My next action is to take into a Toyota dealership to have it hooked up to an analyzer. Has anyone else run into this problem??? The closest dealer is over an hours drive from here so if I can remedy this situation, it would be a huge help.

Has the thermostat ever been replaced? Does it heat up to normal operating temperature as quickly as it used to?

Any chance one of the brakes are dragging? Feel each wheel for excess heat after driving it for a while.

You might find this hard to believe, but cars wear out! At 104K miles, the bloom is off the rose…Those piston rings and valves are simply not as tight as they once were…You can donate $200-$300 to the dealership if you want but I doubt they will find anything…Any decent independent shop can run diagnostics (scan the engine control module) and do a compression test…

Good Luck…

EPA has your mileage rated at 22city/29 highway. Sounds like you are in the proper range and I would not waste a dime at a dealer.

What exactly is your method on measuring 36MPG?

As Caddyman noted, odds are that a trip to the dealer will be a waste of $$. They will charge you a bunch of $$ for a diagnostic (probably a code reading), tell you the computer finds nothing wrong and try to sell you about $500 worth of useless services like “induction cleaning” and stuff. At the end you’ll just be more poor & the car probably won’t be any different.

My own first thing would be, as Goldwing suggested, to deal with the cooling system. Have it serviced, including a new thermostat & radiator cap. And just as importantly, have someone who knows what they are doing check out the coolant temp sensor.

Are the new tires the same as the old ones? Rolling resistance varies across different tires.

A 30% drop in gas mileage is HUGE. 104k miles is NOT that many miles. This has NOTHING to do with age or mileage. I’ve had many vehicles past the 250k mile mark and they all had same gas mileage when new + or - 2 mpg (about 4%)…NOT 30%.

Find a good independent and get it diagnosed. Something isn’t wright. And find it now before it gets worse.

Good answers above, but I would add that you check your transmission fluid. There is no requirement to change the transmission fluid in this model, but I think Toyota was wrong on this subject. If you have never changed it, or had it changed, I think you will find it black instead of red and that could be the cause of your drop in mileage.

Unfortunately it may be too late to fix it with a fluid change, but I’d try anyway. Even if it doesn’t fix the mileage problem, it could delay a complete transmission failure.