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Can new Timing Belt and Water Pump change MPG?

I have a 1999 Camary CE with 87K miles and recently changed the timing belt and water pump. I have noticed that the MPG has gone down from 24-25 to 21-22. Is it possible that the new timing belt and water pump caused this? Thanks

Is a check engine light illuminated?

Check your mileage for three tankfulls and see. Recently means when?

Both of the above are good replies. If your have a CEL the engine already knows something is wrong and you just need to ask it what. It is also very easy to get a bad mileage measurement from just one tank full. Three consecutive ones tends to eliminate measurement error.

I will add that the answer to your question is YES, it can be the timing belt. If it is not installed correctly the valve timing can be off, but before you go there let’s get another tank or two to verify your numbers. You might want to bring the problem to the attention of whoever did the work and see what they might say.

As PDV asked, what is the real meaning of “recently”? You should be aware that the drop in ambient temperatures has led to a drop in gas mileage for all vehicles recently.

As Mr. Meehan noted, an improperly installed timing belt can result in lower mpg, less power, and other problems. But, if the drop in gas mileage took place since the drop in temperatures, it is very likely that you are not observing anything unusual.