Question: what is the difference between 20 and 30 weight oil?
Answer: The difference between 5W-30 and 5W-20 motor oil The main difference between 5W-30 and 5W-20 motor oil is that the latter gives a slight bump in fuel efficiency. ... This translates into the strength of the 5W-30 oil keeping it from breaking down as quickly as the 5W-20 oil, providing better overall engine part protection.