# New tires = very poor mpg for Hybrid! What gives? **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [December 21, 2015, 6:57am UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022 "2015-12-21T06:57:09Z")\ **Posts on this page:** 19\ **Page:** 3
**Author:** ![Honda-Blackbird](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/honda-blackbird/32/3159_2.png) [@Honda-Blackbird](https://community.cartalk.com/u/Honda-Blackbird)\ **Post date:** [December 22, 2015, 10:50pm UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/41 "2015-12-22T22:50:18Z")
I hope he really did buy the " Low Roll Resist " tires…and not just told that he did. Someone may be trying to pull a fast one here. This might be a case of seeing what a regular tire will do to MPG in these vehicles. That would stink. What also kind of stinks is that they have more than one Low Roller tire… It should be a simple matter of…This or That… They should not have degrees in between. But then again…what a great way of increasing profit possibilities. Blackbird ---
**Author:** ![MikeInNH](https://avatars.discourse-cdn.com/v4/letter/m/a587f6/32.png) [@MikeInNH](https://community.cartalk.com/u/MikeInNH)\ **Post date:** [December 22, 2015, 11:12pm UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/42 "2015-12-22T23:12:06Z")
The larger the sample the more accurate it’s going to be. ---
**Author:** ![insightful](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/insightful/32/2732_2.png) [@insightful](https://community.cartalk.com/u/insightful)\ **Post date:** [December 22, 2015, 11:39pm UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/43 "2015-12-22T23:39:52Z")
I replaced the oem tires on my Insight with Bridgestone Ecopia EP422 ($80/tire at TireRack) and saw no change in my normal 50 mpg average. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [December 23, 2015, 12:18am UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/44 "2015-12-23T00:18:02Z")
Did the Bridgestones perform well? Just curious. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [December 23, 2015, 12:44am UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/45 "2015-12-23T00:44:31Z")
**I hope he really did buy the " Low Roll Resist " tires…and not just told that he did. Someone may be trying to pull a fast one here** Yup! I have known tire salesmen to use incredible BS in order to sell what they have in stock, regardless of whether or not it is appropriate for a customer’s vehicle. ---
**Author:** ![asemaster](https://avatars.discourse-cdn.com/v4/letter/a/5f9b8f/32.png) [@asemaster](https://community.cartalk.com/u/asemaster)\ **Post date:** [December 23, 2015, 4:36am UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/46 "2015-12-23T04:36:17Z")
**Did the Bridgestones perform well? Just curious.** I’ve sold many sets of the EP422 Ecopia and everyone has been happy with the ride and performance here in Washington state. ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [December 23, 2015, 5:27am UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/47 "2015-12-23T05:27:41Z")
We avg 51 mpg with our Prius. 1 tire had sidewall damage at 8k miles. I got a new prime well tire and our mileage did not change 1 mpg. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [December 23, 2015, 5:38am UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/48 "2015-12-23T05:38:26Z")
Now this is an interesting conundrum. One might say it is Car Talk’s Christmas Conundrum!! Even if the new tires aren’t quite optimum for the Prius, I can’t see how that would cause a drop in mpg from the mid-50’s to the low 40’s. hmmm … I think the dash display must be the problem. Maybe the fuel use or vehicle speed sensor is out of calibration for some reason. Suggest to measure your mpg using the tried and true method, number of miles driven between fill-ups divided by the gallons required to fill the tank. And check your odometer calibration using those one mile interval signs along the road. You can check the speedometer calibration that way too; it should take exactly one minute between posts at 60 mph. ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [December 23, 2015, 6:45am UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/49 "2015-12-23T06:45:51Z")
Not the gauge, he calculates it the right way. The drop is real, what’s the cause… ---
**Author:** ![insightful](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/insightful/32/2732_2.png) [@insightful](https://community.cartalk.com/u/insightful)\ **Post date:** [December 23, 2015, 8:41am UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/50 "2015-12-23T08:41:23Z")
> _Did the Bridgestones perform well? Just curious._ Very well. New tread depth 11/32". After 15,000 mi, rears at 10/32" fronts at 8/32" then rotated them for the first time a week ago. Dry, rain, snow, no complaints. Same 175/65-15 tires I believe OP’s Prius C uses. ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [December 23, 2015, 5:51pm UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/51 "2015-12-23T17:51:58Z")
Well, if trip mpg meter is “wrong” or not accurate with old tires it should be exactly the same “wrong” with new tires. Mpg was 50 mpg before. It actually might have been 15% off. With new tires it is still 15% off. New tires does not tweak the accuracy of trip meter. Or does meter vary from day to day? ---
**Author:** ![CapriRacer](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/capriracer/32/22_2.png) [@CapriRacer](https://community.cartalk.com/u/CapriRacer)\ **Post date:** [December 23, 2015, 6:21pm UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/52 "2015-12-23T18:21:28Z")
A couple of thoughts: First, the OP says he uses an app to calculate the fuel economy, then he says his morning commute’s fuel economy is different than his evening commute’s. I don’t think those 2 statements are compatible. He also mentions watching the screen. Second, he has a 3 1/2 year old car and apparently recently changed out the OE tires. I’m thinking that means he has quite a long commute - and therefore puts a lot of mileage on the car. It also means that his fuel consumption is mostly caused by the wind resistance and the rolling resistance. That might explain why the drop in fuel economy is so large. The car was reported to be getting over 50 mpg’s and I think that is a lot - again pointing to a commute that is mostly long, uninterrupted drives where most of the fuel consumption is caused by wind and rolling resistance. He also mentions 41 psi in the new tires. That is an unusual value. (I looked up the spec and 41 psi is not it!!) So, what was it in the old ones? Could it have been higher? (Note: One possible explanation would be the OE tires have 51 psi written on the sidewall and the Michelin’s have 41! That might account for some of the difference in fuel economy.) ---
**Author:** ![Docnick](https://avatars.discourse-cdn.com/v4/letter/d/ecae2f/32.png) [@Docnick](https://community.cartalk.com/u/Docnick)\ **Post date:** [December 23, 2015, 7:42pm UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/53 "2015-12-23T19:42:29Z")
After some 10,000 posts, I’m starting to take any comments on gas mileage with a few grains of salt. My first question will be: “How did you measure your gas mileage?” ---
**Author:** ![Honda-Blackbird](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/honda-blackbird/32/3159_2.png) [@Honda-Blackbird](https://community.cartalk.com/u/Honda-Blackbird)\ **Post date:** [December 23, 2015, 8:14pm UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/54 "2015-12-23T20:14:18Z")
If the new tires have a larger outer circumference than the old ones…they will spin more Slowly… and since the speedo was programmed with the value of the circumference of the old tires… There would be your discrepancy. While in reality…you actually traveled further…but…the speedo doesn’t know this…because it is not using the new value of the new circumference. So you would see a big drop in mpg if the outer circumference/RPM of the tire has changed. Blackbird ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [December 24, 2015, 1:44am UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/55 "2015-12-24T01:44:48Z")
**“If the new tires have a larger outer circumference than the old ones…they will spin more Slowly… and since the speedo was programmed with the value of the circumference of the old tires… There would be your discrepancy.”** The speedometer was calibrated to the old tires when they were new, not when they were worn down. If the replacement tires are the same size as the OEM, then they should have the same circumference that the OEM tires had when they were new. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [December 24, 2015, 9:36am UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/56 "2015-12-24T09:36:06Z")
Is a possible explanation that a wheel speed sensor was damaged during the tire change-out, throwing the trip-distance calibration off? Or is the trip distance measured by the normal speedometer/odometer method, using the transmission’s vehicle speed sensor? ---
**Author:** ![Honda-Blackbird](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/honda-blackbird/32/3159_2.png) [@Honda-Blackbird](https://community.cartalk.com/u/Honda-Blackbird)\ **Post date:** [December 25, 2015, 1:57am UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/57 "2015-12-25T01:57:27Z")
I agree that they SHOULD HAVE the correct circumference…but what is the Actual number? It is possible to see differing circumferences between “same size” tires. Also true with the width. Perhaps it is just a defect? Yes this vehicle should be monitoring speed via the VSS on the transmission. There are a lot of variables at play here. Blackbird ---
**Author:** ![rocketman](https://avatars.discourse-cdn.com/v4/letter/r/eada6e/32.png) [@rocketman](https://community.cartalk.com/u/rocketman)\ **Post date:** [December 26, 2015, 8:07pm UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/58 "2015-12-26T20:07:59Z")
So on the other side of this discussion . . . if I change tires and put the Prius tires on my Toyota Yaris will i get better MPG? Rocketman ---
**Author:** ![CapriRacer](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/capriracer/32/22_2.png) [@CapriRacer](https://community.cartalk.com/u/CapriRacer)\ **Post date:** [December 27, 2015, 6:56pm UTC](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022/59 "2015-12-27T18:56:40Z")
Rocketman asked: “…If I change tires and put the Prius tires on my Toyota Yaris will I get better MPG?..” Maybe. It depends on what you take off. If you swap OE Yaris tires for OE Prius tires, then likely No!. That’s because OE tires are generally designed for good fuel economy (by sacrificing wear and/or traction) - PLUS - you’d be swapping worn tires for new (worn tires give better FE than new tires all other things being equal.) But if you swapped aftermarket tires for OE Prius tires, then you’d likely experience an increase in FE - BUT - you’d be sacrificing wear and/or traction. [Previous page](https://community.cartalk.com/t/new-tires-very-poor-mpg-for-hybrid-what-gives/92022.md?page=2)