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New Tires equals worse mileage?

My 2005 Honda Civic Hybrid has been averaging 52 mph since I purchased it last December. Only 38,000 miles old, I’ve made sure to follow all of the maintenance requirements, down to the special herbs in the pyramid.

When I ran over a large piece of metal last week that ruined one tire, I replaced the entire set. I don’t know when I hit it but noticed my tire was flat a few miles from home. There was no big bang or bump. But ever since the new tires were installed my mileage has dropped by 20% and no lightness of the foot seems to help.

I don’t believe that the car’s alignment has spontaneously gone ka-flooey and I have no recollection of hitting anything hard enough to throw it out. The tires are at proper pressure.

Any ideas? Anyone? Thanks in advance.

Cecil Eastman

South Bend, IN

I meant 52 mpg, not mph. In case it’s not obvious.


Well 20% is a lot due to tyres. But tyres can make a difference. Some tyres, including the ones the should have come on your car are low rolling resistance and will give a little better mileage. There are even differences between standard tyres. Make sure the new tyres are inflated to the pressure recommended by Honda for your car. If they are low that could also be part of it. I am assuming you are using the same size tyres.

Also it is not coming up on summer. If you are getting summer fuel (mixed with alcohol) then that will also account for a mileage loss.

Also, are the new tires the same size? Different size tires will result in odometer error.

20% is a lot more than can be accounted for by tires. You will see a mileage drop depending on a tire’s efficiency and size, but not that big. Perhaps it’s a coincidence, but also the tires installed could be taller than the old ones.

  1. The fact that you were able to identify the event that lead to the flat tire says the event was enough to change the alignment. Check it. Even a small amount of misalignment can have a large effect on the drag that the alignment creates. The alignment shop should be targeting the middle of the spec. If they says “in spec” is good enough or that they can’t adjust it because there aren’t any provisions for adjustment, find another shop.

  2. As Joe Meehan indicated, different tires will give different RR results. High wear tires do not give good RR so if that was a consideration in what you purchased that could be an effect.

  3. New tires will have more RR than worn out tires - all other things being equal. This means that even if you replace worn out tires with EXACTLY THE SAME TIRE expect the fuel economy to drop.