In my beetle I run SAE30 oil in winter, SAE40 in summer. I change oild religiously at 3K minle intervals without fail. Aircooleds don't seem to like multi-viscosity oils. If it's below freezing out the SAE20W oil is called for.
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.
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.
According to the manual it takes .625 of a quart and manufacturer recommendation is 5w-30. If it is an older engine that smokes you can use SAE40 to keep the oil from slipping past the rings.
when oil gets hot the particles break down that means it thins out when cold they bunch together making it weigh more or thicker
10w30 is thicker than 5w20
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.