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i remember my ole dad used to get bits of timber or break up pallets to start a fire under the diesel tank to (i think) de wax the fuel■■?
First time I saw him do it, i felt the need to step back quite a bit. 
Yeah. Many a morning I had to light a fire under the tank of my Maggie D tipper. Oh the good old days.
Regarding windscreenwashers i always used to add a small amount of methylated spirits,it stopped them freezing and free from salt.
Dave.