Should the engine be hot b/4 oil change?

All these years I have always brought the engine up to normal operating temperature b/4 draining the oil. Just got to wondering, since I’m using 10-30 oil wouldn’t the oil drain more completely with the engine cold? If the oil is thinner when cold and it is all drained down into the pan wouldn’t this be the best way to go? What are your thoughts. Chuck

 

If possible, change oil warm/hot, you’re doing it right. The thinking that I was taught was it gets impurities and particles mixed in solution, the oil flows better (despite the higher temp “weight”) and it more completely drains down to pan and empties. To an extent, it’s splitting hairs but compare the flow of new, cool oil from the can to hot oil leaving the drain.

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I always change the oil with the engine warm. Even if all I do is drive the car around the block first. It helps the oil flow better out of the pan.

 

^^x2^^

 

I change it hot because it puts more contaminates in suspension and it flows out better...my 2 ¢.

 

This is one of those never-ending questions that has basically 3 answers. Hot, warm, or cold with results all over the map. It's like asking the "what's the best engine oil for my car?"

If you keep a reasonable OCI with quality fills, your sludge build-up should be to a minimum, if at all. If not, you got other issues needing attention. It's likely more of a personal preference as with the likely miles you'll put on it won't be dangerous to your engine either way. It flows much faster out of the engine warm/hot, obviously, but if you're doing it cold while doing other maintenance items, you can just remove the plug and let it drain for an hour or so, do the other things, have lunch, then button it up again. If the oil is dirty coming out, it's holding crap in suspension. You're always going to be leaving a bit of old, dirty oil behind anyway, but with over a gallon of new oil in there, the risk of it being an issue is minimal.

 

It also depends on how long the engine was sitting. If it's coming out of winter hibernation, then I run it until it's warmed up to circulate prior to draining. If I ran it yesterday, I will do it cold.

 

If using thick oil (15w-50) then best to do it warm/hot. If it's thin (10W-30) then you can do it cold. On modern cars that use OW-20, I change it cold. Since the oil is so thin and free flowing when cold, it drains really easily and quickly. If an Olds 455 with thicker weight oil, do it warm or hot.