People in the know use synthetic engine oil instead of regular "dino juice". The top companies spend millions of dollars in R&D to develop the best engine oil possible at their respective price range. If you buy a brand name synthetic engine oil (like Amsoil, Motul, Mobil 1 etc...) they have the optimum blends of additives for maximum engine protection at very low and very high tempteratures. And the synthetic base does not break down at high temperatures or with time and it pours at -51 Celcius (-60 F) so you get instant lubrication on the coldest Alaskan winter night. If you want maximum fuel efficiency a lighter weight oil will be better but depending on the design of the engine and the conditions at which it is driven the lighter oil will not provide as much wear protection.
But the Insight was designed for 0W20 so it should be ok for a long time (at least if you synthetic 0W20)
It is highly recommended that you do not add any additives to engine oils because it will mess up the precise blend of additives companies spent millions of dollars to optimize!
People who race do a lot of modifications to their cars, but one thing they do not do is add additives to their engine oils, they just buy better engine oils!
For the Insight, the best engine oil might be this one
http://www.amsoil.com/products/tso.html
But the Insight was designed for 0W20 so it should be ok for a long time (at least if you synthetic 0W20)
It is highly recommended that you do not add any additives to engine oils because it will mess up the precise blend of additives companies spent millions of dollars to optimize!
People who race do a lot of modifications to their cars, but one thing they do not do is add additives to their engine oils, they just buy better engine oils!
For the Insight, the best engine oil might be this one
http://www.amsoil.com/products/tso.html