dgwhitten

I have an 05 C2. Coming back to Nashville from Birmingham yesterday my oil temp stayed at below 200 for much of the trip. Outside air temp was in the low 40s and it was raining a good bit of the time. I have not seen it drop below 200 before. Is this normal? Thanks

jnx

I would say yes, it's normal.

1999Porsche911

Cruising speeds produce the lowest engine combustion temps as well as maximum coolant cooling and therefore water and oil temps will be near their lowest. A few bursts of the engine and you should see that temperature rise.

OCBen

I'll buy that explanation for low oil temps during cruising, but it doesn't hold water for coolant temperature, as this is regulated and controlled by the thermostat.

1999Porsche911

Coolant temp is no longer controlled by the thermostat once the valve is fully openned which is at approximately 185F. Additionally, oil temperture is directly related to coolant temperture since coolant is used to cool the oil.

OCBen

Like I said, coolant temperature will never drop below 185F as the thermostat will shut off circulation through the cooling system and restrict it within the engine block. Once the temp creeps on the plus side of 185F the thermostat valve opens up again and allows circulation through the cooling system, and shuts it off when it gets on the negative side of 185F if there is too much cooling. The thermostat continues to cycle this way, regulating and controlling the minimum coolant temperature.

That's why I said I agree with your explanation that cruising speeds produce low engine combustion temps and that therefore oil temps are lowest under these conditions. But it is solely the thermostat that controls the minimum coolant temperature once the engine has warmed up. Don't you agree?

1999Porsche911

The point is that once the theromostat is open, it would take EXTREME cold conditions to get it too close again. (the normal, operating temerature of the engine WITHOUT a thermostat is about 189F in optimum conditions) The operation of the Porsche engine, once warmed up, will keep the coolant at 194F only under the best of conditions. (Cool temps and this cool air moving over radiators at 60+MPH. Any condition less that this will result in the coolant temperture that is higher. i.e. driving around town or warmer air temps.

The fact is, your coolant temperature (regardless of air temperature) is seldom below 200F driving around town, which means that your oil temperature is also higher. As soon as the air temperature rise to around 60F, the stock cooling setup will not maintain the coolant temperture below 200F and tempertures can exceed 220F in warmer weather. This is the result of insufficient air movement across the radiators.

When cruising at highway speeds, the amount of air passing over radiators is sufficient to properly maintain coolant temps 194F (Porsche's target temperature). This is why my statememt that crusing at highway speeds lowers oil and coolant tempertures is accurate.

It's all about air movement and fluid circulation and you cannot have lower oil temperature unless you also have lower coolant tempertures.

SFBayAreaGT3

If 194F is the best of conditions, what should the oil temp be at normal operating temps?

Or what is the (best of conditions) oil temp when the engine is warmed up?

1999Porsche911

At cruising speeds, the oil temp should be within 5 degree's of coolant temp. 200F is fine.