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Does gas mileage improve after break-in?

Just curious if gas mileage for a brand new car improves as the engine breaks in. If so, how long does it generally take and what kind of improvements can be expected?

Your engine is broken in within 10 or 20 miles and mileage improvement (if any at all) is so negligible that you would never, ever notice it.

Yes, but any mileage difference is likely to be well below the measuring error.

Many car salesmen are trained to deflect customers’ concerns about the disappointing fuel economy of their new purchases. “It’ll go up after it’s fully broken in. Just give it another 5000 miles.”

Both my brother and I experienced a nice improvement in gas mileage–he with a 2009 Hyundai Santa Fe, and I with a 2011 Subaru Outback, after several thousand miles. Although the engine is technically “broken-in” fairly quickly, we both found that our gas mileage took a nice bump upward after about 10k miles.

Now that I have about 14k miles on the odometer, I find that my average gas mileage is about 1.5 mpg better than it was originally. Not spectacular, but definitely measurable.

It might depend on the car. I didn’t notice any improvement when I bought my Civic and broke it in.

Every new car I’ve owned…it has…Usually after 10k miles or so…But it’s NOT that much…as high as 3mpg.

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My own experience is that there’ll be some minimal improvement. Typically the car will be as good as it’s going to get by 10,000 miles. But my experience includes cars bought over the last 40 years. I’m not sure if it still applies to today’s cars.

Is there a specific reason you’ve asked? If so, give us the details and we’lll try to help.

No specific reason, just curious.

Typically yes. C/D long term tests of vehicles usually confirms a 1MPG or better gain once a car gets some miles on it and everything loosens up.

I think that some improvement in fuel mileage is due to drivers becoming acclimated to the car and sometimes the car becoming acclimated to them.


My vote is with Rod Knox.

Years ago production tolerances had a much wider range and some manufactures set the clearances tighter than others. Studebaker and Packard designed their cars with very small clearances had to " wear in" and frequently got lousy gas mileage for the first 5000 miles. You might have gotten a Ford or Chevy with tight clerances but you had an equal ghance of getting one that burned oil right from nrw.

My car was broken into twice with no effect on gas mileage.


My experience is a little after 10 or 20,000 but never much more than 1 or 2 mpg.

Aw geez, five years later.

After 10k miles–or a bit more–my gas mileage has always increased by 1-2 mpg.
But…was it REALLY worth resurrecting a necro-thread that had been dormant for 5 1/2 years in order to solicit opinions on this trivial topic?

Did anyone else notice that this thread is six years old?

Fuel economy for my car crept up over the first 1000 miles or so and then held fast at a 20.4-21 MPG average ever since. My first tank was 17.7 MPG, then it went up to the mid 19’s before settling into the low 20 MPG range. My typical driving routes (back and forth to work, to the grocery store, etc.) are very consistent. I only take trips that are beyond 100 miles about twice a year. So far the lifetime average of my car is 20.4 MPG, the EPA says I should be getting 15 MPG city, 25 MPG highway, and 19 MPG overall. Which is pretty close to what I get. Recently I got new tires (OEM’s lasted all of 11k miles), and fuel economy has gone up to 21-21.5 MPG over the past few tanks, even with constant A/C use.

Fully agree with you on that point. I’ve noticed that after about one year of driving, my mileage has improved by approximately 2 mpg. I track the driver’s information display and keep a log.

Adjusting to the suspension, handling, etc., plus plain-old breaking a car in - because let’s be honest here… when you get a new car, or new/used, you fool around in it, show it off, and test what it can do. Takes a while for the driver (me!!) to come down to reality and start using the vehicle for everyday practical needs.

Yes but since I don’t really give a rat’s behind…