Karl the clearances are much tighter on today's engine. Oil pressure is the
indicator of "potential" flow, but it's all about flow. If the viscosity is
too high, flow will be reduced, because when there is enough pressure to
lift the ball from the seat in the regulator, that will represent an easier
path and pump flow will be directed through the regulator and not the rest
of the engine. Use the viscosity the factory recommended. They built the
engine, not your son.
Steve

"Karl Townsend" wrote in message
anews.com...
I just got a graco drum pump with an oil quart meter. Set the number of
quarts you want. Put it in the fill hole and pull the trigger. You're done.

I want to get a 55 gallon drum of oil for all my engines. the seven
tractors, fork lift, big truck, and lawn mowers can easily use a 10-40
rated for diesel engine use. Now, my new pickup calls for a very light
5-20 oil. My son says the V8 engine is still made the same way they've
always done it and a 10-40 will be fine.

Anyone know the story on these very light oil specs? Is this just done for
slightly better fuel mileage? My new pick 'em up truck cost damn near 30K
and I don't want to hurt it.

Karl