I just got a 99 gt and the orig owner of it always used synthetic. whats the best weight to use, 5w30 ? and is a regular motor craft filter good to use with synthetic..And I didnt even look yet but is there one or two drain plugs

 

10w in the warm months and 5w in the cold months. All else fails, just use what the oil cap says.

[EDIT] this is a little too basic see my second post.

 

its not a double sump like the 5.0.

should have a single drain plug.

 

For the 99-00 Ford recommended 10w-30. I think it was in '01 they changed the recommendation to 5w-30. I run 10w-30 all year long because it really doesn't get that cold here. But there is nothing wrong with running 5w when its cold.

 

my manual doesnt say 10w-30. where did you see ford recommending that for 99-00?

 

I don't have an owners manual. That is what is says on my oil filler cap. It is also what I've read here on the forums. What does your manual say?

 

30 is the warm temp and it doesn't matter if it's 5w30 10w30 it all runs the same viscosity at operating temperature. The oil needs to be thiner during start up. 5w30 or 0w30 is what i'd suggest if you're in the colder temps and you're not at the track. If it's just a DD 5w20 is good as well.

 

mine calls for 5w20 on the oil cap

 

Go with what Ford calls for!

 

I would really suggest ONE OF THESE

It works really well, I just installed mine last week.