Lark327

The new Hot Rod Magazine came today and had a piece discussing changing your oil hot vs. cold. I've always changed mine hot. They concluded the same thing. But as they explained the reasons, now it doesn't seem so obvious why. For example they talked of how warm oil is thinner and runs off the engine parts easier. I couldn't agree more. Seems intuitive. But,,, it got me to thinking that as soon as you turn your engine off, all that nice hot oil runs off the engine parts anyway and into the oil pan. In fact if you let it sit overnight before changing the oil, the oil has even more time to run into the pan which is where your going to drain it from in either case, So in this instance, it seems more oil would drain into the pan from a hot engine parked overnight, than from a hot engine where you drain the oil a short time after turning it off.
The other reason they gave was that contaminants stay in suspension better in hot oil than cold. I guess I would question that, since modern oils have additives to keep them in suspension.
You may need to let it drain longer to get as much as possible out of the pan when cold because of the increase in viscosity, but if you already waited all night what's a little more time?
Now obviously it would be more difficult and will take longer to get it all out of the pan if temperatures are very low, but in the summer or in mild climates it seems to me that changing it cold would be just fine and would prevent possible nasty burns and some of the mess made when you rush to keep the hot oil off your hands.
Thoughts???

CAMS69

Funny cause, hot or cold there's always a little left in the bottom of the pan...so to me it don't matter

cv67

Some in the lifter valley also...I just do it cold so Im not burning my arm

raycam01_au

cold never bothered to warm it,
I do usually have a hot coffee so maybe that helps

MelWff

Always have done it cold and do other things like checking transmission and differential fluid levels and greasing to give it plenty of time to drain.

7T1vette

You change it when cold so that you won't burn your hands working around a hot engine. Now, if you want to let it run just until it is warm to the touch, have at it. What is the loss by changing when cold? Hmmm....a little 'dirty' oil doesn't flow out because it is clinging to the walls of the engine and sump pan. OK. When you first start it with a NEW OIL FILTER in it, that's fixed!


This issue falls under the category of "Much ado about nothing..."

flyeri

Depends on how much time I have and which vehicle it is. For the Corvette, sitting on a lift where it lives, cold works fine. I will let it drain over night or a day or two sometimes.

Earthquake Driver

Warm, I start the car and let warm up a little.

KapsSA

The couple of times I've changed oil cold I had a heck of a time getting the oil filter off.

C3 4ME

Hmm, i've never thought about changing cold. Makes sense though.

lowbuck72

I'm trying to picture what goes on inside the engine, and if the engine is hot when you change the oil, the bearings are all lubricated so less of this oil is drained, If the engine is cold, most of this oil has run down into the pan overnight. It makes no difference to me which method gets more old oil out. However, when the oil is drained, there's no longer any oil in the oil pump pickup tube. When the new oil is added, I think there may be an air gap in the pickup tube. Upon start up, I'd rather have bearings that are already warm and lubed, rather than risk oil starvation until the pump can feed the cold bearings. It always seems to take a few extra seconds for the oil pressure light to go out on start up after an oil change. That's when the most engine wear occurs. I always change my oil after warning up the engine.

7T1vette

Great 'theory'. Does it have any real merit? It certainly does, for you. But, is there any tangible benefit to justify it?

SEVNT6

My high school auto shop teacher said this was the reason for always changing hot.
Now, that was 45 years ago. But I've always done mine hot.
And I let it drip until I'm done with one beer......

4-vettes

I always change oil Hot, and every professional mechanic I know does the same. Not just that Hot oil suspends particles better. but rather when everything is spinning around, all bits are getting stirred up. cold oil gives it time for "bits" to settle down to the bottom and "Stick" to surfaces.
you want it all stired up, hot, so it flows out carrying all the carbon and sludge with it. Cold, the sludge and carbon can remain stuck inside. Yes, there's always a bit left. No matter what. but stir it up before dumping it!

resdoggie

Hot or cold oil change doesn't make any difference. The same amount of oil will come out the drain hole. What's left inside is an insignificant amount when mixed with 5 qts of new oil. Starving the bearings of oil for a few seconds will not hurt the engine anymore than any other cold start. Yes, there is wear but I may start my engine 100 times between oil changes. How does that factor into wear compared to one start after an oil change? Bearings do not completely drain oil from the surface after sitting for an hour or even days or longer. At startup, the engine is not under any significant load so the bearings can tolerate a second or two without an oil supply. Obviously this is the case or engines wouldn't last as long as they do. Same goes for contaminates in oil. That's why regular oil changes are performed, hot or cold.

walleyfisher

I am willing to bet that changing the oil hot or cold will not damage you motor in your lifetime
Just make sure to put the oil back in it with the drain plug in (Mr. Obvious)

panther-19

I am in the "makes little difference" camp. I have been changing oil in my vehicles for 50 years and have never seen an engine failure because the oil was changed using one method over another. The boats and watercraft I have owned need a pump to suck out the old oil rather than drain out a drain hole so you know there is always some left in there anyway.

Hopper12

Always hot for me. Why? Has little to do with actually changing the oil benefits. It's a good excuse:

Me: "I'm changing the oil in The Beast today, got to drive it to get the oil warm".
Wifey: "How long will you be gone?"
Me: "Got to get it good and hot - probably a couple of hours. I think I'll drive up to Bridal Veil Falls. You want to go?"
Wifey: "Sure"

And off we go for a nice drive that really has nothing to do with warming the oil up - just a good excuse to go for a drive together.

KenSny

This is an excerise in futility.
It's like asking if you should change the filter when you change the oil. Duh!

kingkohlmn

I've kept my car original, the only thing that is not original are the tires. I was able to transfer the original air from each tire to the new tires. My vote is warm, but I have also changed it when cold. Also, I change it once a year whether it needs or not.