How to know which tires are most efficient?

unfortunately, no efficiency standards, so no ratings. not familiar with primewell, but they could certainly be a large part of the problem.

 

Keep in mind that tires have higher rolling resistance when new than when worn. That effect was at least part of the drop you noticed.

 

New tires also have larger OD, meaning the car think's you've travelled not as far, as when those tires are worn down, smaller OD, more rev's per mile, but the car then think you've travelled further. Fairly trivial, but a factor.

One tire I got (on a privious car) that really hit the ground running as they say, was Bridgestone Ecopia EP20. They were OEM on some Prius, only came in 195/65R15 IIRC. And I believe they've been discontinued. When those were put on, replacing worn Bridgestone Insignia SE200_02 (no mpg slouch either), the mpg never skipped a beat.

FWIW, mpg aside, they were very noisy when worn, and a menace in any amount of snow.

Hmm: Canadian Tire claims to have the EP20.

 

Probably Bridgestone Ecopia EP422 Plus. I suspect they gave up a slight edge in rolling resistance, but they're an OEM tire used by Toyota on the Prius, so...

One thing, the EP422 from the factory are a Made-In-Japan version. There's also two other versions, more readily available in the North America: one manufactured in the States, the other in Mexico. All three have physically different tread patterns, and various specs are different. And they all have the same name. One of them, the US itteration IIRC, has very wide longitudinal gaps, one less row of tread, in 195/65R15 at least. There was one member here reported a tire shop tried to sell him 2 US and 2 Mex, when he was replacing all tires.

 

If you buy the Bridgestone EP422 Plus from the dealer, will you get the Japanese version?

 

I don’t think so. Ask? Around here I think dealerships mostly sell just snow tires.

 

Try searching "fuel efficient tires for prius" in your favorite Search Engine

 

With the dearth of accurate LRR data, there could be a buisness model for a website, something like "Bob is the Tire Guy"? Develop a database of opinion, for various factors, LRR included? Maybe it already exists?

 

Consumer Reports tests tire on a dynamometer for rolling resistance.

 

I experienced the same thing this year with my 2020 prius prime. I was getting arount 6-6.1 miles/KWh until I got a nail in my tire after 42,000 miles. I replaced all 4 of my factory installed Dunlop Ensave tires with Michelin X-Tour tires on June 6th 2022. The efficency dropped about 10% to 5.4-5.5 miles/KWh and hasn't appeared to to recover after driving 10,000 miles. You can see a table of my efficency in 2021 and 2022.

Effeciency (miles/KWh)
Month ---------- 2021 --- 2022
January -------- 5.3 ----- 5.7
February ------- 5.8 ----- 5.9
March ----------- 5.6 ----- 6
April ------------- 5.8 ----- 6
May-------------- 5.8 ---- 6.1
June-------------- 5.8 ---- 5.5
July -------------- 5.9 ---- 5.4
August ---------- 6 ----- 5.5
September ---- 6.2 ---- 5.5
October -------- 6.1 --- 5.5
November ----- 6.2 ---- 5.4
December ----- 5.6 ---- 5.2

 

I have a 2000 Honda Insight hybrid. The original tires were a Bridgestone Potenza. I went thru several sets of those tires, they had terrible tread life, but good low rolling resistance. Those tires are getting hard to come by, so the last set I bought were a LRR Dunlop. MPG dropped dramatically, by about 10mpg. The car can no longer maintain highway speed in 5th gear with the AC on. By highway speed. I mean 60mph. That's how bad the Dunlops are. I wish there were published numbers on actual rolling resistance.