0w-30

[circmand]

There is no one answer for this. The type of oil best suited for an engine depends on the engine itself but also season and temperature. Heat thins oils and cold thickens it. So it hot areas you want an oil with ahigh viscosity (resistance to flow) for when the heat thins it. In the cold youi want a low viscosity oil so when it thickens when parked your engine doesnt have to strain against a think mud to turn the engine over. You do not want to go to far in either direction unless the temperature is in a severe cold or hot zone. In addition I beleive altitude can also affect the oil viscosity adversely. So best oil? Like all things it depends.

[AlaskaVX]

I have and will always use 10w-30 in the summer and 5w-30 in the winter.

I have been using Royal Purple 75w-90 in my diffs but I have seen a lot of posts of people using the mobil-1 ??w-140