Hot Versus Cold Oil Change

I usually like to change the oil when it is hot. Even better put a quart of ATF in it and run it for a couple hundred miles then change it after a drive letting it drain for about 20 min or so. The theory being it will drain out of the motor better when it is hot.

But then I start thinking (Always a dangerous thing)

The car has been sitting all night and all the oil is in the pan at the moment. I was pondering just jacking it up and draining it. That way most if not all the oil that can come out of the motor is out. IT is about 55 deg outside so the oil should flow reasonably well even when cold.

Opinions?

One of the main reasons for oil changes to be done while the engine is hot would be that while the oil is circulating, it can keep the dirt in suspension. If you let it settle overnight I'd expect the dirt to settle, which is not really a good idea, is it?

It is better to do it hot. The oil evacuates more quickly. The best part is that the oil filter once warm unfastens much easier. This prevents the "screwdriver mauled and still stuck oil filter" phenomenon

m

Ok what did I do?

I put my block heater against the oil pan (held in place with a jack) and left it there for half and hour.

Oil checked oil temp on the dipstick and ti was very warm. Drained out as usually and the oil seemed to flow out fast. I am hoping that with the application of heat on the bottom that the convection may have put some of settlement back in to suspension.

We will see.

i do it cold because i do not like burning my hands. i usually let the plug out for half an hour or so.

I don't really care with the car, but the motorcycle, I let sit for a good 20+ minutes because Honda decided filters go best behind headers. They cool pretty fast though.

I invariably end up with oil all over my hand/arm and thus change oil cold as not to scald the flesh off my body.

I do mine hot. I also let it sit for half an hour while I do other things.

When I worked for a small firm that did not care, I would go to work 20 minutes early, pull the drain and change the filter. At lunch I would put the drain back and refill with oil

I compromise. Do it with the oil warm.

Warm.

Pontiac put the filter behind the turbo downpipe.

Shawn

I do it warm or hot. About once a year on older engines I'll dump a quart of diesel in the oil and let it idle for 15 minutes to clean out any sludge. Don't rev or drive with diesel in it because the oil is too thin to support loaded operation, but it sure does keep things clean.

The ATF thing certainly won't hurt, but it also doesn't help much. People assume that ATF is such a good cleaner, but its not. They associate clean transmissions with the oil it uses, but the reason a transmission stays clean is because it doesn't have to deal with blowby and carbon associated with an engine. The ATF itself isn't really any better at cleaning.

I owned a MR-2 SC at one point and I would have to drop the car off at the service station early in the morning so that it would cool before the oil filter was removed. There were numerous reports of flash fires on MR-2's. Miata arent quite as bad and blood loss is a greater risk.
I did replace the belly pan on the GTO after the first oil change with a SLP sump guard to prevent the risk of serious bodily injury from the belly pan falling on me. OEM pan weighs over 20lbs!

pres589 wrote: I don't really care with the car, but the motorcycle, I let sit for a good 20+ minutes because Honda decided filters go best behind headers. They cool pretty fast though.

Don't remind me. I was the one to do the changes on my Father's Night Hawk It REALLY sucks when he decided to just use Honda CAR oil filters and you had to drop the headers to get the bigger filter in. On the up side, filters where cheaper, easier to find, and more filter material.