synthetic oil

[Anthony]

Now let us go back to the Ferrari recommended parameters in my 575 Maranello manual. It calls for 75 PSI at 6,000 RPM. The pop off pressure has not been reached. As we now increase the RPM we still get an increase in flow rate. This is what we need and this is exactly what they are recommending. We get our maximum flow at the maximum system pressure, at about the maximum engine RPM of 7,700. There is no bypassing of the oil. All oil pumped goes through the system. There is no wasted BHP pumping oil past the bypass valve back to the oil tank. It is the perfect system.

Finally I will compare a single, 30 weight oil, at normal (212 F) and at racetrack (302 F) temperatures:
(A) For a 30 wt oil at normal (212 F) operating temperature:
RPM....Pressure..Flow
1,000......20 PSI....1
2,000......40 PSI....2
4,000......80 PSI....4
8,000... 160 PSI....8 *
* Note : The maximum flow because of the oil pop off valve at 90 PSI will be 5

(E) For a 30 wt oil at elevated (302 F) operating temperature. The oil is thinner at 302 F. It requires less pressure to get the same flow:
RPM.... Pressure. .Flow
1,000...... 10 PSI.... 1
2,000...... 20 PSI.... 2
4,000...... 40 PSI.... 4
8,000...... 80 PSI.... 8
Note : The maximum flow because of the oil pop off valve at 90 PSI will be 9

The hotter (302 F) 30 weight oil is thinner than the cooler (212 F) 30 weight oil. It has the same flow rate in the constant volume oil pump but at a lower pressure than the oil at normal operating temperature. This allows for a doubling of the flow rate at peak RPM. The thinning of oil at higher temperatures is a benefit. You get more flow, more cooling and more lubrication. The 30 weight oil at 302 F has the exact same flow rate and pressures as the 20 weight oil at 212 F. See (D) above. Therefore, use the 20 weight for around town driving and the 30 weight on the hot track. You get maximum flow at each situation.

For YOUR engine, substitute the actual flow at 1,000 RPM. If your engine puts out 1.5 liters/min. at 1,000 RPM it would put out 3 liters/min. at 2,000 RPM and 6 liters/min. at 4,000 RPM and so on. The maximum flow in (A) would be 7.5 liters/min. In situations (D) and (E) you would get a maximum of 13.5 liters/min.

Conclusions:

The reason that multigrade oils were developed in the first place was to address the problem of oil thickening after engine shutdown. Over the years we have been able to reduce the amount of thickening that occurs. Never-the-less there is no oil that does not thicken after you turn your engine off. This is why we have to warm up our engines before revving them up. Engine designers always pick the recommended oil based on a hot engine and hot oil. There is no issue with oil thinning as they are both matched when hot. The problem is oil thickening when the engine cools. Cold engine showing very high pressures because of the thickened oil at startup:

For a 40 wt oil at 75 F at startup: The oil is thicker, has more internal resistance and therefore requires more pressure to get the same flow.
RPM.... Pressure.. Flow
1,000...... 60 PSI.... 1
2,000.... 120 PSI.... 2 *
4,000.... 240 PSI.... 4 *
8,000.... 480 PSI.... 8 *
* Note : The maximum flow because of the oil pop off valve at 90 PSI will be 1.5

At 1,500 RPM you reach the maximum oil flow rate and if you run to 8,000 RPM it is the same rate. The flow cannot increase and it is insufficient. This is why we must wait until our oil temperature comes up to 212 F or higher. The maximum flow rate in this case will then double, up to 3. To get even more flow in our test engine you need to use a lower viscosity grade.

If you have absorbed and digested the information here you should be able to pick out the proper operating oil weight for your car, be it a 30, 40, 50 or even 20 weight oil. I have always used oils that were a grade thinner than recommended even though many use a grade thicker than recommended. I showed evidence that the starting grade should always be 0 or 5 (0W-XX or 5W-XX for thicker oils). If you want the best protection and highest output from your motor use a synthetic based oil. The actual brand is not as critical as the viscosity. The rating must be SL or the upcoming SM rating. Change your oil every 3 - 5,000 miles and at least every spring.

Final examination to follow later.

THE END