[LEWISMATKIN]

I know this goes against the recomendations of most, but unless you live in a cold climate for at least 6 months of the year, I recommend a single weight series 3 diesel engine oil preferably SAE 40 for several reasons. Zinc content, which has previously mentioned, is one. Second, I recommend single weight oils for the reason that a single weight oil gives more cushion than a "mulit-viscosity" engine oil. Engine oils do not get thicker when the oil temprature rises. If you want to see what your multi-viscosity oil looks like at 200 deg. F., mix one quart of your oil with one quart K-1 Kerosene. That oil is super thin, and has no cushion. Years ago, a Standard Oil distributor (now called Chevron) told me what the mulit-viscosity rating means. The first number (using 10w-30 as an example) is the base of the oil. In a 10w-30 oil, the 10w is a SAE10 winter grade oil (approx SAE 8) with the additive package that gives the oil the surface tension of a SAE 30 oil without the body or cushion of the SAE 30 oil. Our V6 engines came from the factory with more verticle oil clearance than the typical passenger car engine. As a dealer fix for the "covey of quails" noise upon initial start up, my dad would install .002 U.S. rod bearings in a customer's engine to stop the noise created by the verticle oil clearance of the connecting rod bearings. In giving my reasoning, I only seek to ensure the longevity and protection of the bearings and other moving parts of these engines.

cordially,
Lewis Ellis Matkin, Jr.
Ridge Manor, Florida 33523
1965 1002 GMC V6-305E (soon to be 401M)