[trackbird]

As I was laying in my 40 degree garage today, changing the oil in my Camaro that had been parked since the night before, I remembered that most people seem to recommend changing oil when it is hot, so it drains better.

Now, my question is.

If oil is thin when cold (for start up protection) and gets thicker when it heats up, is it really a good idea to change it "hot". It did seem to take a while for the last of the oil to drain today, but I'm not sure that it should have. It was just an observation, early today, before I really woke up. So, if it is thin cold, and "thick" hot, shouldn't we change it cold? Or should we?

Just wondered what everyone else thought.....


(Nata, if this "takes off", kick it to engines or I will, it's a "general question" for now, isn't it?)

[robz71lm7]

Pull up a MSDS on 5w30 10w30 or whatever you use. It'll usually state the viscosity at 40* C and 100* C in cst. It's thinner at 100*C. Oil thins out as it gets hot. Ever notice how you have lower oil pressure when your engine is up to operating temp?

The 10w30 label sorta says that it acts like a 10 weight would when it's cold and like a 30 weight would hot. They add viscosity index improvers (VII) to the oil so it won't thin out as much when it heats up. A lot of synthetics require less VII than conventional. Some claim to require none.