I have a 347 fuel injected motor in my Cobra. I have used 10-30W dinosaur
oil for 40,000 miles. I tried Mobil 1
synthetic for a year but it was so thin it would leak out.
Valvoline VR1 is the
oil to use in old motors that need
zinc and other additives.
We know this because one of our Cobra buddy has a brother in law with Valvoline test lab.
VR1 has the same stuff in it as Joe Gibbs.
Parts store sell VR1 for $7 a qt.
Dwight