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
The larger the sample the more accurate it’s going to be.
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.
Did the Bridgestones perform well? Just curious.
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.
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.
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.
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.
Not the gauge, he calculates it the right way. The drop is real, what’s the cause…
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.
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?
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.)
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?”
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
“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.
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?
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
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
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.