215/75 vs 195/80 fuel economy

Having picked up a full set of SZ4 steels with Duelers fitted, I finally had the opportunity to do a direct comparison between them and my 215/75 G015s on SZ5 alloys.

Warmed the car up and did a 4 mile route at 50mph with cruise control on, got 40mpg dead with the 215s.

Swapped over to the 195/80s, warmed the car up and ran the same route again, got 42.3mpg. Similar difference on return route too.

215s were showing as 30psi on TPMS, 34psi on my gauge when cold. 195s were set to 28psi on my gauge (tpms hasn't picked them up).

Wheel/tyre combo weight differences are:

Steel wheel with 195/80R15 Bridgestone Dueler = 17.85kg
Alloy wheel with 215/75R15 Yokohama G015 = 21.5kg

So there is a noticeable difference in economy between the two, but not sure it's enough to make me stick with skinny tyres

And i'm happy if i get 25mpg

I normally average 33ish, but this was a nice flat road with no traffic around, so constant 50mph from beginning to end.

My memory is questionable but I'll try.... 215/75x15 is 2144 rolling diameter and the 195/80x15 is just under at 2117 I think...

The 195's will be better in mpg not just because of the diameter suiting the gearing but also width, they have less rolling resistance and that matters a lot with mpg figures. The extra mass of the bigger tyre will also increase drag significantly.

sniper