Oil Change 2700 miles

[Dakota_imp]

The viscosity of a multi-grade oil like 10W30 or 20W50 changes with temperature. Viscosity is simply the ability of an oil to flow. The first number/letter, eg. 10W is the viscosity in winter temperatures and the second number is the viscosity at high temperatures.

Misconceptions:
1) oil viscosity has nothing to do with its ability to carry away heat or cool an engine.
2) Oil viscosity has little to do with its ability to reduce friction.
3) Harleys and some other bikes generate very high cylinder head temperatures, especially near the exhaust valve. Using a 20W50 weight oil supposedly allows the engine to better tolerate those high temperatures. However, that may be simply due to old fashioned thinking. Indy racers typically run very low (0W) viscosity oil to get faster flow thru the engine and coolers and require less power to pump the oil.
4) Synthetic oil is not necessarily "slicker" than petroleum oil. That capability is largely a factor of the friction modifier additives in the oil. The main benefits of synthetic is the ability to tolerate extreme temperatures and the ability to not break down over time.

I don't know that I agree with that. The higher the viscosity, the greater the head, and the lower the coolant flow. I would also guess that a higher viscosity would have less turbulent flow which would reduce cooling effectiveness.
Found an article that discusses the improved effectiveness of lower viscosity oil due to turbulent flow: http://www.nynas.com/Segment/Transformer...r-cooling/

It is for transformer cooling but the science is the same:

Heat exchange factor is important

The heat exchange factor plays an important role in the cooling of a transformer. It is actually a matter of heat exchange between the oil and the windings. This factor is highly affected by viscosity. The Reynolds number (Re) is the parameter that is used as a measure of the heat exchange factor in the transformer industry.

The Re value also shows whether the oil flow is laminar or turbulent. Laminar flow means that there is an even layer of oil along the boundary between windings and oil. In a turbulent flow this layer is disturbed and the oil is constantly mixed, so that new parts of the oil phase continuously come into contact with the windings. This means that cooling is much more effective with a turbulent flow.

The connection between Re, flow speed and viscosity can be represented thus:


The lower the viscosity, the higher the Re value. When Re is higher than 2300 there is a turbulent flow.