A few questions please.

1) What is the optimum oil temp? What is the danger oil temp?

2) What is the optimum coolant temp? The danger coolant temp?

3) What is the optimum tranny temp (A4)? What is the danger tranny temp?

Thanks in advance for your imput.

 

Here are the numbers I was running on a 300 mile trip today. The outside temp was mid 90's F.
Water Temp was 196, Oil Temp was about 205 , Tranny Temp was around 177 with a tranny cooler .
Hope that will give you some idea.

 

The danger oil temp is 320 degrees F if you believe the GM engineers although you wouldn't want to leave it there for too long.

Coolant you need to keep below 260. although 240 is probably a more conservative danger temperature.

 

TTT

I am curious about this topic too.

 

I was driving in the mid 90 degree outside temp. Without the AC I was running a coolant temp of about 210-220. With the A/C on the temp shot up to as high as 245 in traffic. Seems high to me. anyone else?

 

My understanding is that A4 tranny life is negatively impacted whenever temps get above 190'.
Not to say you will have anything immediate happen, but tranny life incurs a more negative affect than normal, with temps above 190'. HTH.

 

Nominal oil temp is 212F. There is no specific number that you can really call a danger temp for the oil. As the oil heats up, the viscosity goes down. A typical 30 weight oil has a viscosity of 10-12 cSt at 212F. That viscosity lowers to about 3-4 cSt at 300F. Are you comfortable driving around with an oil that is 30% of nominal? I'm not. Which is why I run a High Performance 10w40 on the track where my oil temps are routinely in the range of 240-255F. I'd feel comfortable with a 30 weight below 240F.

Coolant:
When the car starts and the coolant is cold, the thermostat will remain closed so the fluid doesn't circulate to the radiator so it heats up faster. The thermostat will open at about 194 or so allowing fluid to flow to the radiator. Once your car is warmed up, the thermostat thus sets the low temp because if really cold air flows through the radiator cooling the coolant below 194, the thermostat will go towards shut, reducing flow to the radiator and the coolant will remain at about 194.

On the high end, the temp is controlled by the fans. Though the fan setpoints appear to have varied slightly over the years, they are about: low speed on at 226, off at 219; hi speed on at 235, off at 226. So in stop a go traffic, it is not abnormal to see temps in these ranges.

Other things to consider are that when the AC condensor is on, the fans will run, thus if it is hot enough out for the AC to run and the fans are on, but the load on the engine is low or airflow through the radiator is high, the temp will go down to the 194 range where the thermostat will go closed again.

The car can reach an equilibrium in between 194 (thermostat closes) and 219 (fans come on) dependent on engine load and airflow/airtemp flowing through radiator, thus you see many guys say their car runs near 200-210.

A4 temp - can't help you there...