Does changing the size of a muffler affect the mpg of the vehicle?


Asked by Jul 07, 2014 at 10:31 PM about the 2006 Toyota RAV4 Sport

Question type: Maintenance & Repair

Can someone help out this Navy Vet? Have a  2006 Toyota Rav 4 Sport [ 4 cylinder
automatic]. Noticed [heard] a sound emitting from my stock muffler and after inspecting
it, noticed hot air blowing out along the seams on both ends due to rust, wear, and
age.  Recently, had the stock muffler [32" x 14"]switched with a generic smaller muffler
[20" x 10"] . Although there have been no issues as of yet, it seems that I am NOT
getting the gas mileage that I once was and , actually , visiting the gas pump a bit
more. Could this be true, and if so, any recommendations? Importantly, I must add that
I do mostly in town driving and my surroundings have MANY hills which we drive daily.
Anything from anyone?

4 Answers


That sounds like the smaller muffler you put on has caused an exhaust restriction, I would recommend getting a good Hi Flow muffler possibly a Magnaflow or something similar. The larger the capacity of the muffler the better the flow, but be careful with higher flows also comes more exhaust sound, trying to find the happy medium can be tricky, a good exhaust shop can help.


Hi tennisshoes, and thanks for taking the time to answer. Still, would it affect the mpg? I mean , would exhaust restriction affect the mpg of the vehicle?


Yes it can, if the engine can't breathe it won't run efficiently therefore it takes more fuel to provide the same amount of power. Your engine needs to get rid of exhaust as fast as it can.


Yes, I agree with Tennisshoes. Unless you put a straight through muffler like an old school Thrush Glasspack, then I would have to say, nope. Look elsewhere like clean air filter and spray clean your mass airflow meter / sensor and throttle body - see youtube video: Hope this helps.

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