I just took the first highway trip on a set of "new to me" Michelin winter tires 185/60r14.
There's a fair amount of vibration from being out of balance, and it had me wondering how much it affects fuel economy.
It has to affect it
some, after all
... a bit of the fuel being burned was being converted into shaking the whole car up/down/around, rather than just propelling everything smoothly down the road.
The
crappy winter mileage of this trip (compared to warm spring temps) had me wondering how much of an effect it was. Probably not huge, but these are the things a fuel economy geek thinks about while tooling down the road.
So I wondered: how much power would it take to shake the car around to the extent I saw? 100 watts seems a reasonable estimate. So, roughly equivalent to running with headlights on vs. off.
That's my WAG, and I'm sticking to it.
100 watts represents about
2.2% of my car's power requirement for going down the road at 45 mph in pleasant conditions. (In "stock" configuration, according to our
aero/rr calculator.)