So I'm going to begin working on a 1968 Mustang with the inline 6 today. First thing up is going to be the oil. What weight should I be putting in? I know MY stang takes 5w20. Should I go with the same for the 68? Thanks

 

10w-30 should be fine...

But then you get into the whole mess of running an off the shelf oil with low zinc levels made for modern engine without flat tappets.

The idea is an oil like valvoline VR1 racing oil has high levels of zinc / phosphorus which reduce wear on high friction surfaces such as non roller cams and rockers and the off the shelf oil may not provide adequate protection.... you can also buy a zinc additive to add to an off the shelf oil so it acts like the VR1 oil.

-Gun

 

Personally, I'm a fan of 20w50 for the warmer places but as PP stated, you need to find a source of zinc to keep engine wear to a minimum.

 

I use only 10W-30 in my 200 I6. I however do not run an oil additive since I have noticed nothing wrong with the car on regular oil.