I recently bought a 2003 Toyota 4runner V6 and it is coming up on the first oil change. I don’t know if I should use a synthetic oil or just oil ect. The manual recommends using 5w-30 oil. But a friend of mine said that if I use synthetic oil I would have problems with my seals in the long run. I live in San Jose Ca and thinking of using 10w-30 because it doesn’t get that cold out here. I will not go over 3500 or 5,000 miles on the oil changes. Any suggestions?