Doing things because that's how you were taught

[donkmeister]

I was changing the oil on one of my cars over the weekend. I was about to turn the engine on to warm it up first, when I stopped and thought "why am I doing this?". Well, I was taught that you get the oil warm before you drain it.

In winter, I suppose warm oil runs out more quickly than cold oil. Especially so with old types of oil. But I'm sure I was taught "running the engine will help push the oil everywhere and clean out the dirt". Well, what will it pick up that it didn't get on the previous run? Isn't the oil in the sump now just as dirty as it would be if I run the engine for another 10 minutes?

I drained the oil, room temperature, just the dirt that was already in it. Only difference was the removal of burn risks, and that there might have been a few teaspoons more oil drained out because it wasn't splashed around inside the engine first.

So, is there another reason I should have run the engine first?

Have you got any spannering habits that make no sense in the modern world?

[ian332isport]

Historically, it was to make the relatively thick oil a bit thinner, so you get more out. These days, modern oil isn’t much thicker than water, so not such an issue.