oil cooler

[bobcowan]

That is true. Oil viscosity drops as temperature climbs. Oil also breaks down the longer it is exposed to heat.

Oil is predominantly heated by RPM's. extended rpm's that you'd see in road racing. street and highway driving generally don't create enough heat to worry about, except in the most extreme desert conditions.

For most street cars, oil temp tends to hover right around coolant temp.

Oil has a minimum operating temp, too. It's really hard to find out what that number is, as manufacturers are not willing to let that be known. But it seems to be around 180*F. Perfect operating temp seems to be right around 200-210*. In a race car, it will usually be between 300-350*.

I often drive when the temps are pretty cool. I found that even with a thermostat it was sometimes impossible to get the oil up to operating temps, even when the cooler was covered.

If your oil temp is consistently above 250*'ish, then it's probably worth it to install a cooler. Otherwise, use a true synthetic and don't worry about it.