It's the majority, but overwhelming or not surprisingly appears to depend on car model, at least per some calculations someone on reddit ran [1].

I'd add though that rolling resistance tends to be higher, on average, in winter too. When there's often a bit of snow on the roads... Less so on high speed highways admittedly.

[1] https://www.reddit.com/r/askscience/comments/l2cq6b/comment/...

Oh yes, by so much.

Even at 30kmph it's already the majority of the resistance and it scales exponentially with speed so you can imagine how much it matters.

Considering air resistance is proportional to the cube of the speed, it would be highly surprising to not be the case.

Define ‘high speeds’. There’s a reason race cars look like they do, to the point of having serious problems driving at speeds just a bit below highway speed limit.

Yes it is.