[embee]

Winter fuel has more volatile fractions than summer/intermediate petrol to aid cold starting. See "Reid vapour pressure" or RVP. Manufacturers (of cars anyway) usually do cold start tests down to -35C unassisted (i.e. no block heaters or supplementary batteries). In climates where temps below -35C are seen regularly folk usually take extra measures (leave running, block heating, garages etc)


................but we're going off down a different track I think.