10w40 is thicker (but only when hot, they are the same thickness cold.)
That means the oil is 15 weight when cold and 40 weight when hot. The higher the number the thicker the oil.
In cooler temperatures it's ok, but in hot weather run a thicker oil.
40 is thicker. 20w 40 means its 40 weight at normal and hot temps and 20 weight at winter temperatures. 40 stays 40 at all times.
20W50 is the " thicker " oil
5W-30 is when it's hot. They are the same when both are cold.
The higher the number the thicker the oil.
Engine oil does not get "thicker" at high temperatures it gets thinner.
10w30 is thicker than 5w20
when oil gets hot the particles break down that means it thins out when cold they bunch together making it weigh more or thicker
Oil is thicker than water because oil has larger molecules that are more tightly packed together compared to water. This makes oil more viscous and resistant to flow compared to water.
only if your engine has trouble keeping the oil pressure up. If it hasn't a thicker oil won't do you any good.