alright, have some questions about oil. i have 158,000 miles on my 85 t/a. it leaks alittle but i think its coming from the valve covers so i will replace the gaskets. i am going to use mobil oil and ac delco filter. i was wondering if i should flush it? with what and will it hurt it? and i was also wondering if i should use 10w30 or 10w40 oil?? adn synthetic or regular, i heard u shouldnt run synthetic in an lg4 but i dont see why.

 

Saying not to run synthetic in a specific engine, is bad advice IMO. Now, I would fix that leak first then worry about synthetic. The leak will prolly worsen with synthetic, and Mobil 1 is pricey enough for an oil change, let alone replacin lost fluid.

 

i'd run 5w -30 in cold and 15w-40 or 15w-50 in heat