Oil change - drain hot, warm, or cold?

[Barkleymut]

Sorry if this has been discussed before....Something my grandpa always told me was to drain your oil when the engine was hot. After thinking about it shouldn't you drain when all of the oil is in the drain pan? It just seems that when the engine has just been turned off it could take hours for the oil in the "nooks and crannies lol" would take a while to drain.

So am I correct in my assumption that a cold engine is better to change the oil on? Plus an added bonus is that your forearms do not get 2nd degree burns when your arm inadvertantly scrapes the exhaust!

 

[sunfire]

Its already been discussed but the topic never gets old. Hot or cold... light or heavy oils.

https://bobistheoilguy.com/forums/posts/1485431/

 

[hpichris]

Feeling hot hot hot.

 

[XS650]

Draining hot gets the oil moving the faster and takes the most gunk from the bottom of the pan with it. That's because the hotter oil has a higher Reynolds number, therefor a thinner boundary layer so the pan has useful flow closer to the pan surface.

The crooks and grannies drain fast enough on a hot engine.

I don't think working on a hot engine is worth the small improvement in drain quality, so I drain when the oil temp is about 100F.

Hot drains meant more in the olden daze because sludge was a bigger problem then.

 

[Triple_Se7en]

Drain it hot so the sediment at the bottom of the oil pan gets removed better.

 

[GROUCHO MARX]

Just like cleaning a frying pan, hot.

 

[soldierman]

I like to change mine a short time after a good long drive. I usually let it cool off enought to avoid burns but still hot enought that it drains quickly and any gremlins are still suspended.

 

[Jimmy9190]

I always drive over to Napa to get my oil and filter then back to my house to change my oil, which brings my engine to operating temperature. But I don't like getting scalded by hot oil either, so I let mine cool off for a half hour or so before I pull the drain plug. It gives me time to jack the truck up and set my jack stands in place, get my tools and drain pan all together under my truck, plus I inspect the undercarriage and suspension, brake lines, etc while I am waiting. I also find it's a whole lot easier to remove my oil filter after I let the engine cool.

 

[hate2work]

No matter what you do, you cannot get 100% of the old oil out anyway. Lately I've been a fan of draining the oil after the engine cools a bit, that way when I remove the filter I don't get assaulted with extremely hot oil.

 

[TallPaul]

I don't think it matters that much, so long as it was shut down hot. Worst is when you leave your car at a shop for service and ask them also to change the oil. I bet sometimes they will fire it up cold, drive it into the garage and drain the oil. A lot more left behind that way.

If you have a drain valve, cold will take forever to drain.

 

[pepper32]

Hot.