Oil changes...When engine is hot, warm or cold???

[PassnThru]

My brother-in-law had two engine failures in his Dodge pickup, before I learned his oil change routine was to flush the engine with gasoline before adding the fresh oil, to "make sure everything was cleaned out". I no longer discuss any mechanical topics with him--he is beyond help.

And the sad part is he is probably cruising internet forums right now putting down:
- Dodge because he had two engine failures
- (his brand of oil) because he had two engine failures
- (his brand of oil filter) because he had two engine failures

Such is the advice on forums - you never truly know the source.
Having said that - people here seem much more grounded in their responses and experience although this thread alone has shown people have their biases. But - no one has yet said - I always changed my oil in my last car cold and my engine failed so it has to be that!
That's a really good thing

 

[jethro29]

hot is best,if you really want to get the old oil and sludge out.

 

[mhm993]

warmed up

 

[chrommagman]

I have change mine cold, warm, and hot.
I think changing it wile it is hot is the best! it drains faster and it will loosen any **** that is in the sump.

 

[fflintstone]

Hot!

 

[Aklass]

I prefer warm/cold every try doing an oil change on an older toyota where you have to stick your hand next to the exhaust manifold to remove the filter? And I hate it the most when a customer comes in 30 mins late off the highway and wants an oil change done in 20 mins, it can be done but I end up scalding my hands in the process.

 

[Ironcrow]

Usually cold. It doesn't matter much at all one way or the other, but its nicer to work on a cool engine.

 

[onething]

I agree with Aklass. A friend told me how he does it, and I liked the idea.
Hot car in the air, pull the plug, go in the house and come back in 30 minutes. The oil is drained, the engine is cool, and I can put my hand up in the little crevice where Mazda hid the oil filter.
Same on the wife's Caddy, but the filter is where it should be, right beside the drain and easy to remove.

 

[shoot summ]

hot is best,if you really want to get the old oil and sludge out.

I have change mine cold, warm, and hot.
I think changing it wile it is hot is the best! it drains faster and it will loosen any **** that is in the sump.

These comments crack me up, have you really thought about what you are saying here?

So if the engine is cold there is all sorts of sludge and **** that wont drain out?

Seriously?

The engine is hot, the car is parked. All of the sludge and **** settles into the pan. You drain the oil the next morning and all of the sludge and **** comes right out with all of the oil that drains. The same amount of oil that drains if the engine is hot. If you drain it like I do with the front of the vehicle raised, and the drain plug faces the rear of the vehicle most of the oil drains. What little is left, let's say 2oz at most, is now dispersed amongst the 224 new oz of oil that is put in the engine(7qts for my truck). So the 1 percent of the contaminated oil, that might have suspended sludge, ****, polutants, and **** is going to have a dramatic affect on the life of the engine.

NOT!!

It really doesn't matter, but there is no data based justification for either method, just urban legends....

 

[4BT]

Since you somewhat brought it up, Ive heard a few people say they run ATF through the system briefly to help flush it out. Then drain it and put in engine oil.

probably the same people who recommend spraying a mist of water into your carb'd car to "remove carbon buildup". I won't lie, ive tried the ATF trick and it only succeeded in thinning out the oil

 

[Greatbear]

I prefer hot for a couple reasons. By hot I mean after the car has been driven, but has cooled enough as to not be uncomfortable to work with, and has mostly drained back to the pan. The oil drains faster, and if there might be anything suspended in the oil, it stands a better chance to be taken out. The primary reason I prefer "hot" changes is that restarting the engine after the oil change will be a bit less "harmful" as there is still a bit of warm oil up on the bearing surfaces, cylinder walls, etc. Even when pre-filling the oil filter there is always that period of time where the engine is lacking in lubrication until all the oil galleys, pump, pickup and such fill up with oil. Since startup wear is greatest in most engine designs, having the fresh oil "preheated" a bit along with the greater amount left on surfaces means less of a chance running "dry" for any more time than necessary. I've changed oil in cold engines that needed an alarming amount of time to build up pressure, especially in cold weather.