Oil Weight Question?

[Huck BB62]

Thicker oil will cause you a mileage drop. There's alot going on with the oil. It not only lubricates (a lot of people actually think that oil's primary job is to be slippery), it acts as a medium to carry the heat away and acts as a hydraulic fluid. A thicker oil takes horsepower to pump and for the parts to move around in it. Try stirring a spoon in water, then stir it in honey. That's an exaggeration, but that's the general idea. Thicker oil will NOT make your engine run cooler. A thinner oil actually gets rid of heat easier. It takes the heat from the engine part faster and transfers it to the cooler easier. This is because laminar flows. The higher the viscosity of an oil, the thicker the laminar flow is and the heat transfer is not as efficient. Laminar flow is the dead area of fluid adjacent to whatever it's flowing against.

The new engines run great with 30 weight oil. The tolerances are much closer, the oil is much better. Thicker oil thinking is of the past.

The engineers actually take into account the tolerances, the rpms, and other parameters of the engine design when they spec the oil for the engine. Following the recommendation is a what we should do.

The viscosity improvers that change it from a viscosity of 5 when cold to a 30 weight when warm are actually long chain polymers that coil and uncoil at different temperatures. When these break down, this is why your oil drains like water when the oil's old.

Using thicker oil is particularly bad for your engine when the engine is cold. It doesn't get pumped to the top end as quickly as a multi viscosity of the proper viscosity. At the very worst scenario, a bearing could be damaged because the oil wedge that a journal bearing is designed for (again depending on the bearing clearance and rpm) may not be proper when a thick oil is used actually causing bearing damage. (revving your engine when it's cold is a sin for this very reason) This is also one of the merits of a synthetic oil, it's pour point at cold start is far superior to any mineral based motor oil.

Stay with the 5W-30, better yet, get one of the good synthetics (my favorite flavor is Royal Purple) they're all superior to mineral based.

I follow the GM oil monitor. I'm getting almost 10k between oil changes so the cost for a premium synthetic oil and oil filter (Mobil 1 M1-206 is the correct critter for the job) is not worth worrying about for the extra protection offered. Changing the oil any sooner is a waste of resources.