Unsticking an unused engine........

in ref to question above

diesel fuel.... safest can't even light it by flicking in a match or a cigarette
waxy stuff....

low enough viscosity to get everywhere but doesn't evaporate much so you don't risk an explosive situation, don't use petrol...!

diesel left for long enough grows mould and bacteria in it... just keep that in mind before eating

diesel engine oil is just like petrol engine oil with more detergent to deal with diesel combustion particulate pollution of the oil. its the fuel you want