Go to Tyres on the drive.com for some of the new tyre ratings for tyres sold in the UK/EU the first column is the rolling resistance or economy. Makes interesting viewing. I am using the Hankook kinergy eco's rated B size 205/55/16.
Keep in mind that the ratings are voluntarily submitted by the tire manufacturer. That being said, it's better than what we get in the U.S.
The ratings are not voluntary they are compulsory as from next month. They are submitted by the manufacturer but results are being checked. The thing I noticed was how few tyres are given B ratings "the highest rating possible at the moment" to push manufacturers into more development of rolling resistance. From what I can see from initial searches only Michelin and Hankook have B rated tyres for RR and traction this in the 205/55/16 size that I use.
I had a look in my tyre size of 195/60/15 and couldn't find a single tyre with a rating better than "C". Even your "Hankook kinergy eco's" are only rated "C" in this size. I was interested to see what the Bridgestone Ecopia EP100's were rated (as that's what I'm currently using), but there is no mention of them.
These results are only from one retailer and for the tyres they stock. As more companies adopt the new regulations more results will become available.
True but not all tires will be checked. So it is sort of like our EPA ratings here. The Ecopia EP001S is A/A rated.
All tyres have to be tested except remoulds off road tyres and other special applications. See ETRMA - ETRMA-European Tyre & Rubber Manufacturers’ Association
Hey those new tyre markings are cool. You can tell the old tyres (old as in models prior to this year) as they don't have the ratings. I'll certainly be using this website to purchase my next set. I like the Michelins that are BA rated but watch out for the other variety that has an identical name but an EA rating. What's the score there? I'm also surprised by the Hancooks as last time I used those I swore I'd never again as they were rubbish in the wet (and that's the polite version!).
They must have moved on I find them a great tyre. Chose them as they came as standard on my last car "a Hyundai" and liked them so much so when I found they did a LRR tyre I had them put on the Prius.
The only unfortunate thing about these ratings is that they do not give any indication of how fast tyres will ware, but it is envisaged that this information will be included in the future.
It is interesting to note that it is possible, "as I have already found" that by going up in tyre width with careful choice of tyre it is possible to improve fuel consumption even though this may increase aerodynamic drag. From the results of the information on RR from the UK/EU tyre information labels in general the 205 section tyres have lower RR than the 195's of the same manufacture. This is partly born out by the fact that when I changed from 195 section tyres to 205 section "admittedly from OEM Bridgestones to Hankooks." My MPG improved even before the tyres had fully bedded in, and this does not take into consideration that the OEM tyres were worn lowering there RR.
At low speeds the wider tire will have less rolling resistance. The wider tire also increases aerodynamic drag though. For a Prius c driven in the city this is not a problem.
My motoring mainly consists of English country roads at speeds of 50 to 60 MPH, so lots of bends, braking and accelerating. I am still getting around 64 MPG UK gallons. I seldom use motorways except for holidays or airport runs.
That is still pretty slow. You have just entered the area where aerodynamics play a larger role than rolling resistance. Still, it would be difficult to say whether a narrower tire or wider tire would be better in your case all things being equal. If the narrower tire caused you to slow down in the corners more than the wider tire then I give a nod to the wider tire. The problem is, it's almost impossible to keep everything equal. Most people change the model of tire when they upsize or zero size. This ruins the test completely. Even sticking with the same model is problematic unless load and speed ratings stay the same.