MGB: While on the subject of oil changes.....A question

How important is it to drive and heat the oil/engine up before doing an oil change? I've always wondered what is the exact purpose of this. Does it drain faster? Does the hot oil help clean the engine better? My car sits overnight in a garage that maintains a nice
90 degree temp here in the summer. Couldn't I just put it on some ramps in the cool(LOL) AM and drain it out?

it gets stuff stirred up so solids (aka "sludge") will drain with the oil.

oil temps on a warm engine is about 150 degrees or so. good bit > ambient, not quite what coolant usually is.

Thank for piping in Mac. I guess I'll get up early for a drive to warm it up and change it. Question is how early, watching the news the other morning and at 5:30AM and it still was 89 degrees.

You will probably get some mixed responses to your question, but by heating up the engine/oil you will suspend more of the contaminates in the oil which will be removed when drained. The heated oil will drain faster but it has to gravitate down from the rocker assy to the pan which might take longer than if you just pulled the plug on a cold engine that sat overnight.

no need to drive it, just run it for about 5 minutes.....and if you do not have a magnetic oil plug then use a good size round one or square one on the pan in frontof the plug.

I don't warm any engines up, makes it too hot to work on.

Well running it for 5 minutes wouldn't get the engine as hot as full run. But it would still put oil on the rockers which it would have to drain down from. So wouldn't it make sense to just get her as hot as you can. Being hot it will run down from the rockers even better... I'm just interested in which technique is best myself. I do have a magnetic drain plug. How about every other oil change do it hot and cold. he he How about that?

Full running temperature will ensure faster and more complete draining, in addition to other reasons posted above. When cold, you have to wait a very long time for the dripping to stop.

I usually plan my oil changes after a good day/evening of driving, pull her into the
garage, stab some holes into the filter, pull the plug and let her drain overnight.
In the morning I install the new filter, plug her up, fill her up and hit the road again.

ted

15 min of driving is enough. in the driveway, if necessary. but to the donut store and back is good.

mac townsend Wrote:

thomasbenham Wrote:

Maybe someone has asked this before .When the oil is drained from the engine block does oil not remain in the oil cooler and pipes and will this not contaminate the new oil.If so how do you avoid this?

If you wanted to be 1/100 (1/1000?), you could disconnect the oil cooler hoses and drain it, too. Or you could be like the rest of us and not bother.

I like Ted's approach since you drain hot oil but you work on a cool engine. Best of both worlds. Either that or get your mechanic to do it. At least leave the hood up overnight so you remember the next day you don't have oil or a filter!

The small amount of oil remaining in the cooler and pipes is better than the large pockets of air you create by draining them. Sure you can fill it up again by hand, but then you have a mess to clean up and the oil change goes from 20 minutes to 90 minutes. And then what do you do about all the oil still in the engine where it can't be drained? Time for a rotisserie so you can turn the car upside down and empty all those little pockets of oil!

Or you can just change the oil the normal way and not worry about it, as Derek said.