Synthetic motor oil "group" categories

I see reference to various groups of 1-5 in regards to synthetic motor oils. It looks like most of them being sold today are Group 3 (cheaper ones), 4, or 5. I always see people saying that the Group 4 is better than 3 but what about 5? Is this a situation where 5 is better than 4 or would 4 be considered the best overall synthetic oil? I am not sure if this is a situation where a higher number is better or if the higher number is just a different category. I know that some of these synthetics are created from animal/vegetable oils while others are refined petroleum oil.

The reason I ask is because I understand many of the Group 3 synthetic oils would not meet the definition of a synthetic oil in Europe and that oils sold for European vehicles tend to have a higher concentration of Group 4 oils.

I have been told the cheapest Group 4 oil is the Mobil 1 0W40 synthetic which is commonly found for very low prices at Wal-Mart and parts stores when it is usually on sale with a filter included.

Time for a visit to But unless you have one of the cars with non-standard synthetic oil grade specs (VW, BMW, and some GM, for example), it’s not something I’d spend much time worrying about…

Shelf Space…It’s getting to where you need an airplane hanger to store and display all the products called “Motor Oil”…

I remember using the old cardboard oil cans, I recall using Sears brand oil and Co-op dual season motor oil. This was in the 80’s. There wasn’t even a weight listed on the coop brand.v

Here is another question. If you want the best oil money can buy, do you want a group 4 or a group 5 oil? I am not sure which is better. I understand that group 4 oils are specified for some of the most expensive cars on the road but am curious about if group 5 is even better or the higher number just represents a different category of oil.