Increase in MPG/K&N

[richfzs]

Never switch the aircon on, so not that. Suppose driving style may change slightly - but the winter tyres are on from (roughly) mid Nov  to mid march, and there's only ice as such on a fraction of that time. Roads are of course generally greasier though, so maybe. (and when it is properly icy/snowy, I am often guilty of enjoyment - rear wheel drive is great fun, at the expense of fuel :-))