Tyres and Fuel Consumption

[jbanfie]

Having swapped my summer for winter tyres on my wifes Mini Countryman I've seen a significant improvement in fuel consumption, here's the detail:

Summer tyres - Pirelli P7 Cinturato RUN FLAT's - these are E rated for roll resistance C for grip and 71db noise
Winter tyres - Hankook Winter I-Cept RS - which are C rated for roll resistance and C for grip, 72db noise

I take my boy to karate twice a week, so four identical journeys each week which I always use as an mpg challenge - just for something to do. The journey is an 11 mile round trip.

Best I could get on the Pirelli's is about 55mpg, last night I got a whopping 60.4, it's quite a drastic improvement, the journey is all around 40 to 50 mph, so more on roll resistance than wind resistance I guess.

You can see the difference on the instantaneous mpg readout, much better figures at cruising speeds.

I was hoping to see a difference, but am shocked and pleased by the results.

Fortunately I think that all the standard tyres on the A6 are at least C spec for rolling resistance, so that's good.

The dry road grip on the winter tyres isn't as good, but that's no surprise, interestingly despite the figures above, we think the winters are quieter.

Regards

Jon

[OddBallBoy]

Not quite sure how they work out the rolling resistance, how it relates to tyre width. Meaning would a 225 section tyre with a C rated rolling resistance actually have the same rolling resistance as a 195 tyre that is also C rated, or is the rolling resistance only relevant to other tyres of the same width? One would presume the former...

[Steve Hut]

Think my winters are quieter as well though only had the car three days and got winters on yesterday. Dropped a wheel size to 18's on aftermarket alloys. Bit hard to say about fuel consumption as car only done 700 miles but was doing 43mpg on 19's and 41mpg on 18's winters.