Synthetic Oil Improvement in /6

I don't think its all synthetic, Brad Penn does it the old-school way. The higher amounts of zinc will protect mechanical lifters from corrosion newer oils won't.

Now, i'm not going to be a salesman for them, nor do I believe they make the best oil product around, but they are good at making oil for older motors, they market to muscle-car-era owners. (Although a slant 6 is hardly one!)

I'd go with the 10w-30 #7150 for everyday driving, but at $12 a quart, it must be as good as synthetic for top dollar!