motor oil 5-30 vs 10-30
5-30.......threre's no need to use something as heavy as 10-30.
5-30 is all around even. its thinner than 10-30, so it starts in colder weather better. but when the engine warms up, there is hardly any difference.
use thicker oil if you have alot of miles, both oils have the same viscosity cold...30 weight, then the viscosity changes when engine oil is warm 5 is then thinner than 10 w 30. there really isnt alot of difference between the two.
Define hot, and a 10w-40 is better for the 4.0. Its an old school design with big bearing clearances. The thicker oil keeps it happy. As an FYI to the rest, the 1st # on oil is its viscosity when cold. The 2nd # is the viscosity when hot.
Everything you ever wanted to know about oil and lots more --- http://www.bobistheoilguy.com/motor-oil-101/
The W stands for Winter. It is the viscosity on a cold start. When the engine reaches operating temperature, the viscosity is the second number.
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