the_buch

Yes, it would be interesting to know, given the choice, what temperature to run at for least wear. One speculation is that better gas mileage and/or lower emissions in Normal mode would result from a lower friction environment and correlate with lower friction-related wear, and this would be offset by possible other forms of heat-related wear??

acoste

I can only speak for the BMW which does the same thing. When under high load it heats up the thermostat with an electronic heater so it opens at a lower temperature. There might be a slight change in the efficiency in the burning process but I guess that's very little. The lubrication gets better.

The lubrication depends on the oil flow. The higher the flow is the better the lubrication is = less wear. The oil flow is proportional to the oil pressure and inverse proportional to the viscosity (thick oil barely flows).
There are 2 opposing things happening with higher oil temperature:
- The viscosity of the oil decreases (it gets thinner).
- The losses on the oil pump are higher with the thinner oil (more oil gets past the pump seals).
But as long as the oil pressure drop is negligible compared to the viscosity change (oil pump is not worn), the oil flow becomes higher with the temperature increase.

From the fuel consumption point of view there are 2 benefits:
- with the higher oil flow the lubrication gets better = less wear and less resistance
- the oil pump needs less torque to pump the thinner oil = better efficiency

Higher oil flow also means lower bearing temperature due to the heat transfer.

the_buch

If I understand these tradeoffs then, and assuming you're right , wouldn't I want to run in Normal at the higher oil temperatures with less wear until I need Sport for other reasons? And, certainly during warmup when I want to get to operating temperatures as quickly as possible? However, how about a speculation that I'd burn more oil at higher temperatures as things 'loosen up a bit'?

acoste

Yes, it runs in normal mode (high temperature mode) until you start driving it hard.

And in theory it does burn more oil however I don't need to add any oil between oil changes (7k miles) on my car so I guess it's not much.

If you have a LOT of time, read this: https://www.ferrarichat.com/forum/th...e-this.136052/

the_buch

Something from hotrod.com (though perhaps for different use??):

"For a dual-purpose car, engine oil needs to be at least 220 degrees F to burn off all the deposits and accumulated water vapor. For every pound of fuel burned in an engine, the combustion process also generates a pound of water! If engine sump temperatures rarely exceed 212 degrees (water’s boiling point), the water will mix with sulfur (another combustion by-product) and create acids that can eventually damage bearings.

As for ultimate power potential, the general consensus among most racers is that hot oil and cool water make more power in most engines. Cold engine oil causes excessive frictional drag on the bearings and cylinder walls. A quality conventional motor oil will tolerate oil sump temperatures of up to 250 degrees, but starts breaking down over 275 degrees. The traditional approach is to try to hold oil temperatures between 230 and 260 degrees. Even on a short-duration, drag-only combo where oil is frequently changed, I would not want to routinely see under-200-degree oil temps."

PCA1983

I only run my C2S with X51 PowerKit and PDK in Manual mode with Sport mode on, unless on a dry track - then I go to Sport+. Normal max oil temp is about 202-208. I like to cruise at about 3000 rpm and have no use for SC Normal or PDK Auto modes.

the_buch

Wow ... I think he answered the very last question in the quiz appropriately

Thanks for sharing, Doug

acoste

I find 212 deg F excessive.
First: the engine oil is hotter than oil sump temperature so the water has plenty of chances to get evaporated plus
it doesn't need boiling temperature to get evaporated.

There is an observation that the oil level increases if the car is driven for short distances only and the engine never reaches the operating temperature. This is due to the moisture collected in the oil over time. Up to ~10 ounces.
If someone drives this car for more than an hour, the oil level will go back to normal. And this happens to cars with normal 90deg C thermostats.



This is water injection into the combustion chamber. It's cooling the chamber so air/fuel mixture can tolerate higher compression and avoid getting self ignited.

PCA1983

I only run my C2S with X51 PowerKit and PDK in Manual mode with Sport mode on, unless on a dry track - then I go to Sport+. Normal max oil temp is about 202-208. I like to cruise at about 3000 rpm and have no use for SC Normal or PDK Auto modes.

Valvefloat991

No it's not. It's simply an observation that charge density and detonation resistance is higher with low coolant temperature, while engine friction is lower with higher oil temperatures. There's not much doubt about this.

However, this is unachievable in the 911, where the oil is cooled by an oil/water heat exchanger. Thus, once the engine is warm, the oil temp will always be higher than the coolant temp.