Just as a calibration point, my wife was really nervous in her 2008 base model. The tires that were on the car at purchase were new on the front, but OEM, and the car's behavior in wet weather was skittish to say the least. At that point, we were getting around 45+ MPG at 45 psi front, 43 rear. I put new Goodyear Assurance All-Weather tires on it, and my wife immediately said that she never knew she could fall in love with tires before that. Much stickier, much better control, no tendency to slide around in the rain. And the mileage steadily dropped down to 40 MPG + or -, which is about an 11% drop. It's stabilized at that level now, and I get why, but it's frustrating. I'll take delivery of a 2012 Prius V next week with the 17" wheels and new Toyos on the car, and I'm curious how that will work out. I know that the V is rated at about 40 mpg in town anyway because of it's bigger size, so that same level wouldn't be surprising. But has anyone else seen that kind of drop with just a change in tires?
That’s just about the maximum difference tires can make. Most of that would come from the difference of rolling resistance of the tire models. So old tires had small rolling resistance and new tires have big rolling resistance. I could not find the rolling resistances for those tires (Did not really even look as the new tire model sound weird (probably just North American market tire). Rest of the difference would then come from the difference between new and used tires. When the tire wears it gets smaller and then your odometer will read more when driving the same distance. That will make the fuel economy appear worse. But it’s very hard to compare fuel economy between fill ups as conditions and routes are never exactly the same.
and you changed them at a time when colder weather brings lower mpg's and reformulated gas may be part of the equation. but yes, those in the know here generally try to balance mpg's and the right kind of tire for their needs.
I would not conclude the drop is due to the tires, colder air is more dense and winter fuel will drop MPG by as much as 15% overnight (many areas mandate a fuel switch on a particular day). Tire size has nothing whatsoever to do with MPG (16", 17" 18") as long as the vehicle is designed for the size being used. The G2 was considered to be "optimistically rated" in terms of EPA ratings, newer models are much closer to reality and that is the biggest difference today.
Thanks for the heads-up, that's not good. I've gone from worn Bridgestone Insignia SE200_02 (the OEM LRR tire on our previous 06 Civic Hybrid), to Bridgestone Ecopia EP20, and mpg never skipped a beat. It can be done. I suspect when you've got a new tire, if it's got higher rolling resistance and you're asking the tire shops, they tend bring out the platitudes about new tires, give it time, and so on. There's maybe a slight credence to this, but not that much. If your mpg does come back, I'd say it's due to your trying harder.
I don't have experience with Gen2 or V or any of tires you mentioned in OP, so no comments on those. That said, driving Civic Hybrid, Gen3 Prius, and now PRIME, I use to chase for the most fuel efficient tires to put on it. From Yoko Avid Ascend I put on HCH, OEM Ecopia EP20 on Gen3, then Ecopia 422 plus, then Conti Truecontact, and Michelin Xice3, OEM Dunlop Enasaver on PRIME and now Xice3 again on it, they were all LRR tires and gave excellent mpg. But trade off was those LRR tires were either short lived treads, or very noisy and uncomfortable, or not suitable on driving on snow or ice. Tire selection is always compromise, you trade off fuel efficiency for other characteristics of good safe tires. With current low price of gas, the saving by LRR is not likely to pay it self off, beside I am a age, I want more comfort on my car ride than anything else. I may end up paying a few hundred more by the end of life of tire, but if it gives me comfort I desire, I think I will take that. I am currently thinking of taking an advantage of the Firestone Black Friday deal on Assurance ComforTred Touring Tires | Goodyear Tires with $100 off and $160 rebate, $114MSRP tire can be had at $49/tire. BTW, your mentioned Goodyear Assurance All-Weather tires is also on deal with $100 off and $200 rebate from Goodyear. That makes $129MSRP price down to $51/tire.
That’s why it’s good if you can get separate tires for summer and winter. Of course this really depends on where you live and so on. You can get then summer tires with low rolling resistance and good wet grip and even low noise and good ride. And you can get good winter tires with low rolling resistance and good grip on snow and ice and even low noise and good ride.
I've had Michelin Xice Xi3 on both Gen3 and PRIME for winter and love the tire. For Gen3 there was absolutely no mpg hit compared to Ecopia 422 Plus, but were superb on snow and ice. I just put them on my PRIME and seeing over 10mpg down compared to OEM Dunlop Enasave. This is primarily due to driving on snow and very cold temp hit our region day after I put on the snow tires. I am hoping over the course of winter the mpg will recover to that of OEM Dunlop. That said, my next summer tire may not be LRR for increased comfort level.
That change is far smaller than people expect from the amount the tread wears and thins, because this isn't how tires really roll. Tire rolling circumference is determined primarily by the length of the steel belts beneath the tread, not by tread thickness. These belts don't shrink with age and wear. Put another way, the tire contact patch on the ground is flat, not circular, so the normal circle equations don't work when figuring the affects of incremental dimensional shifts.
I just bought those exact tires today at Belle Tire (only operates in IN, OH, and MI) $485.72 out the door $90 rebate "Black Friday" check comes in mail within month from Belle Tire $70 Michelin reward card comes in mail. Grand total after rebates: $325.72
