5W-20 and 5W-30 both pour the same when putting them into the engine and when the engine is first started which is 5W. As the engine reaches normal operating temperature, the 5W-20 thins into a 20 weight oil and the 5W-30 thins into a 30 weight oil. Both of these weigh less than 5W weight oil. So I am confused about the benefit of 5W-20 as opposed to 5W-30.
Also, in regards to 10W-30, the oil pours out as a 10W weight oil which is thicker and heavier than a 5W weight oil. When normal engine operating temperature is reached, both 5W-30 and 10W-30 have thinned into 30 weight oil which is lighter than 5W and 10W oil.
It just seems to me that 5W-30 is the best weight to use for most cars unless something like 10W-40 or 20W-50 is recommended.
Also, in regards to 10W-30, the oil pours out as a 10W weight oil which is thicker and heavier than a 5W weight oil. When normal engine operating temperature is reached, both 5W-30 and 10W-30 have thinned into 30 weight oil which is lighter than 5W and 10W oil.
It just seems to me that 5W-30 is the best weight to use for most cars unless something like 10W-40 or 20W-50 is recommended.