What is the difference between SAE 30w and 10w30 motor oil?

Answer 1

30w refers to the viscosity of the oil. 10/30 is a mixture with 10w wich is more viscous. The reason multiviscosity oils are used is so that when the motor is first started the lower weight oil will get to the top of your engine more quickly. This helps lube overhead cams and internal parts while the 30w oil is still too dense ( too cold ) to get to the top. Most of the wear on your motor happens during the initial startup. If your repair manual recommends 10/30 you should use it.