Preferred Engine Oil for your 72 340 Mopar

rotella T 10-30 with a 1/3 dose of ZDDP. Rotella T by itself has a nice level of ZDDP 1000 ppm, has excellent protection against oxidation and sludge, and is cheap to buy by the gallon. It is a really heavy duty oil.

Perfect.

With the exception that it would be better if it was 5w30. But at 12-13 dollars a gallon I reckon to take it slightly easy on cold starts.

or a good synthetic 5w30 with a full bottle of zddp. Expensive as hell. Last for ever.


What do you do with the engine / car? What is your rear end gear? Do you have a thermostat in it? What temp?
What is the max / min temp where you live?

Just out of curiosity.

Usually with a good thermostat and a good working cooling system, you can run synthetic 5w30 or if you prefer thicker, 5w40 all year round as the engine temp will be constant after it gets past the cold start or hot start, so your oil viscosity should be stable as well.

I live in a moderate climate where it never gets below 30 and I keep the car in my shop so it is never actually 30 in my oil pan. So, I can get by year around with 10w30 rotella T.