From a cold start, (say 40F degrees if you techies wanna get picky) and you allow the car to idle, Which reaches optimum running temperature first? I don't have a oil temp gauge so I'm curious. And yes, I know the oil will heat up much hotter than the coolant.

Answers COME TO ME!

I would say coolant b/c it is way thinner than oil.

The coolant flows around the cylinders and will heat up quicker I think. Plus I get warm air from my car a lot sooner than my oil temp guage moves.

And the coolant is hotter than the oil. My oil temps range from 50-70°C when driving (122 - 158°F) Once or twice on the track I've seen it get 90°C Coolant is above boiling at normal atmospheric conditions, which is why the system is pressurized.

>I would say coolant b/c it is way thinner than oil.

You are right water will heat quicker on a relative basis, it takes on and gives up heat faster than oil but that's not the reason the coolant warms up faster. It is one of the reasons they use water as a coolant and not oil though. It has more to do with where it circulates. Coolant circulates throughout the motor to cool the motor so it's by all the things that get hot. Oil OTOH is there to lubricate firstly preventing things from heating up, it will also cool though I guess.

Coolant. Agreed. :D

-scu

On a typical cold start at 8deg cent with normal urban driving my water is at operating temp (84cent) after 4.5mls but oil is only 54deg cent.
The oil stabilises in the 80-90 bracket when at operating temp subject to load on the engine but it will go to 125cent + on very hard track work.
It can take upwards of 6mls for the oil to reach 80 deg cent and on a really cold day even after 20mls urban comuter driving the temp may only be in the 70s cent.
In other words it takes far longer than most people appreciate for the engine to warm through to full working temp and even more so in winter.

Thanks for the insight! I always let my car warm up a bit before going on boost, these things are good to know ;)