[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?)

[zlexiss]

Let me try to add my version of it:

Multigrade oils still thin out when they get hot. But they don't thin out as much as a straight weight oil does.

So at room temp, a 5W-30 oil is as thin as a stright 5w, which is thinner than a straight 30w.

When hot, the 5w-30 thins out only as thin as a hot 30W, while a straight 5W would be a lot thinner.

So, you get oil thin enough to pump when cold, but doesn't get too thin when it's hot so parts stay protected (as film thickness decreases when the oil thins out)

-Jeff