Engine builder says to use valvoline 20w50

[chas350]

Originally Posted by 1968SWBBigBlock

The real scoop on oil thickness
Your engine builder told you to run 20w50 oil because he built the motor on the loose side of the tolerance band - he needs the thicker oil to fill the bigger gaps in the bearings
This is not a good or bad situation - (a loose engine spins faster and makes better HP - a tighter engine will run smoother and last longer)
We run thinner oils in todays engines because they can maintain a tighter tolerance in the motor that works well with lighter weight oils.
Regarding what oil has zinc content and what oils do not - this is a moving target and nothing is written in stone - the oil company will not call you and tell you they changed the formulation - PROTECT YOURSELF - buy and use a good high quality additive that adds additional zinc back into your oil.
Many of the oils mentioned in this thread have changed formulations in the last 24 months - old tried and true may not work and it will be a costly lesson to learn when the cam fails.

Agree 100%. I don't believe Shell Rotella has Zinc anymore....The only oils with zinc to my knowledge are racing oils like the Joe Gibbs line etc.
From everything I have read, normal everyday engine oil, shell,pennzoil,amaco, etc has had zinc & phosphorus removed to protect catalytic converters and emissions.

If your motor has a flat tappet cam, don't fool yourself, its just a matter of time before you wipe the cam lobes. New oil is not the same, just because its the same brand/weight/package etc. GM EOS (engine oil supplement) is the stuff to use, Lucus also has a comparable product, for additives if you want to continue using your "old faithful brand" you need this!