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Can somebody explain why my winter set of wheel/tires gets better mileage in almost summer temperatures? At 14-17C+, my winter tires give me 29 avg on a test route, while summer gives a ~24 avg. I expect quite opposite numbers at this temperature. What could be the reason?

I have a VW Passat with 2 sets of wheels/tires:

  1. Summer 18 inch with Hankook Ventus v12.
  2. Winter 16 inch with Michelin Xice3.

The weight difference is #1 20.1kg vs #2 20.0kg. Circumference difference with current thread wear is within 1 inch.

  • I'd guess that this is because the Summer ones are larger and as far as I know, larger tires usually mean worse fuel economy (larger also means wider, not just bigger circumference). 18" for a Passat seems like a lot to me. Can you also supply the widths for them? Also tell us what engine does your car have? Another reasons could be quality, Michelin usually advertise good fuel economy. – Alin Purcaru Mar 21 '16 at 11:10
  • That's quite a difference, are you sure its just tires? my difference between winter and summer tires at season change when roads are clean and its not that hot yet always been negligible and fitting with a small size difference between the two sets... – Erik vanDoren Mar 21 '16 at 12:55
  • Are you sure it isn't a change in fuel blend moving from winter to summer blend? – Pᴀᴜʟsᴛᴇʀ2 Mar 21 '16 at 17:21
  • Seems like only wheels/tires. Recently I had to swap winter to summer and summer to winter again within 2 weeks for unexpected long trip through a mountain pass. I'll swap to summer again soon. Gas is always Costco. – Timur Sadykov Mar 22 '16 at 1:37
  • Could be that circumference difference while driving is actually much bigger due to difference in tire profile? 18 inch tire just don't flex that deep as 16 inch. I've measured it while being removed from the car. – Timur Sadykov Mar 22 '16 at 1:40
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I would assume for that same reason as eco tyres. As winter tyres typically only start giving decent grip at temperatures below 7 degrees Celsius, the lack of grip at the temperatures you are using them is effectively reducing rolling resistance.

Perhaps you are also subconsciously aware that you'd take longer to stop and have less grip in the bends so have adjusted your driving style to compensate.

  • Aren't winter tyres simply made of a softer compound? Which would mean they would be softer in warm temperatures, if at all? – I have no idea what I'm doing Mar 21 '16 at 11:31
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    My personal experience with using winter compounds in the summer was very poor grip and very fast wear. – Steve Matthews Mar 21 '16 at 11:52
  • they do wear down very fast, took one set down in one summer back in the day (old, still unused, winter tires that needed to go and no money to replace bald 4 seasons)... – Erik vanDoren Mar 21 '16 at 12:41
  • It is true that they wear faster, but that's because they're softer. Grip could be worse, since they're designed for snow/ice. But I would find it hard to believe that they give better fuel economy, since they're soft. The reason should be elsewhere. – I have no idea what I'm doing Mar 21 '16 at 13:08

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