Howes or PowerSource in the trucks and tractors all year around, every tank full. Only once, and I don't remember why in happened, but it involved me limping into a truck stop and buying PowerService 9-1-1 to put into the tank to unwax my injectors. Obviously it had cooled way down, and obvisously I missed a dose of prevention. Winter versus Summer? Like you, I don't care every tank, so to speak, so that never happens again.