Refers to the ability of a liquid to flow. An oil with high viscosity
is very thick and flows slowly; an oil with low viscosity flows
It indicates a condition where the valve is not held tightly closed in
the seat even though the camshaft has not opened it. Also called
total clearance in the valve operating train with cam follower on
camshaft base circle.
Through the use of computers, the precise time when the valves open
and close can be altered. It may be better to change the timing
slightly when the engine is at a higher RPM than when it is slower.