Warm fuel mixed with trans fluid, assuming you have an auto trans.
Else, fluid that is at or near coolant temp. The MPG gains would be slight, if even present, but it couldn't hurt, so do it and report back!
__________________
"¿ʞɐǝɹɟ ɐ ǝɹ,noʎ uǝɥʍ 'ʇı ʇ,usı 'ʎlǝuol s,ʇı"
|