[teknochild]

we all know we shouldnt rev the engine out in the morning until the oil is at operating temp

but what about after you have been parked for an hour and come back to still warm oil (happens to me a lot after my one shot classes) im sure most of the oil has dripped back into the pan by then, and i know it takes time for the parts to be fully saturated with oil after startup regardless of temperature, but how long really


this also got me to thinking WHY do we wait for the oil to reach "operating temperature" synthetic oil has the same viscosity over a VERY broad range of temperatures, so unless you live somewhere where its 30 degrees out theres not going to be much of a diffrence in viscosity especially compared to normal motor oil

[Corey]

I live somewhere where it goes well below 30 degrees. But anyway the oil isn't the only reason to let the engine reach operating temperature. Efficiency and emissions are at their worst when the engine is cold whether or not the oil is at an ideal operating temperature at 30 degrees F. A warmed up engine will typically idle around 15:1 air/fuel ratio. When cold this can be as high as 4:1 a/f, and even higher while cranking. Also engine tolerances are designed with a certain operating temperature in mind. Most thermostats keep the water temperature around 180-195 F. Running the engine hard too far above or below this will lead to premature wear.. although now that they're making blocks out of magnesium or whatever the 335's is made out of (I'm no metallurgist) I'm not sure how much this applies.

[andrew20195]

Originally Posted by teknochild

this also got me to thinking WHY do we wait for the oil to reach "operating temperature" synthetic oil has the same viscosity over a VERY broad range of temperatures

The viscosity rating determines how thick the oil is across the temperature range. Assuming you have a 5w-30 oil, it acts like a 5 weight oil at 32F and a 30 weight oil at 212F. The problem is that a cold 5weight oil is still more viscous than a hot 30 weight oil. The oil needs to be warm to flow quickly and fully lubricate the engine.

If you've ever drained oil on a car that sits overnight in 70F weather, and compared it to one that has been warmed up, it's easy to visually notice the difference whether you're using synthetic or not.