Oil changes: hot or cold?

**Mom** · 23rd March 2010, 21:30

Hot or cold?

Right you bunch of smart, educated and intellegent bikers answer me this. Was having a bit of a discussion at work today about magnets on sump plug bolts and other places around engines. Good idea, no doubt about it. Collects up all those pesky tiny slivers of worn metal inside your engine. The big debate came about when we started talking about warming the engine oil prior to draining it.

I say warm it, makes it less viscous (thinner) and easier to drain. Apparently if you do that all the metal bits are redistributed around the engine and stick there. I say the magnet deals with that.

A quick hands up at work gave 50/50 on warm up first, others reckoned drain the oil cold.

So, what is the right answer?

**Owl** · 23rd March 2010, 21:53

Hot I reckon

**merv** · 23rd March 2010, 21:58

Yep hot, that's what your manual always says. Then leave it to drain a while.

**quickbuck** · 23rd March 2010, 22:00

Hot....
No question.

Just don't burn your hands on the headers trying to get your filter off!

As for the "Metal getting disturbed inside your engine" I call BS!
The filter will catch that.

If you have metal running around in there it will get in your bearings and wreck them quick smart!
It pretty much goes straight to the filter as soon as it gets created.

Also, the magnets will pick up the bits that contain iron, but there is much metal in your engine that is not ferrus...

If you want to give yourself a heart attach, cut open your filter one day and see how much it catches....

**Bikemad** · 23rd March 2010, 22:03

Yep............as above..........

**howdamnhard** · 23rd March 2010, 22:18

Do it when it's hot. It would have to be flowing really fast to remove the iron bits from a magnetic sump plug. The filter does most of the removal,the magnetic plug just lets you know something is on the way out.

**MaxB** · 23rd March 2010, 22:24

Hot always, for reasons already mentioned.

Be an interesting time at work tomorrow esp. if you're a 'majority of 1'.

**CookMySock** · 24th March 2010, 06:23

There is no point to a hot drain. Think about it for a while.. All it does is help you get the very last bit of the oil out of the bottom of the sump, and what's the point of doing that when you just undid all the goodness of an overnight drain of the top-end of the engine - by starting it!

Don't start it and push the old oil all through the engine. Leave the bike overnight to completely drip down internally, and then drain it cold and let it drip into the tray for an hour. Tilt the bike left and right if you are able, to get the last bit out of the sump. Wipe the filter housing out with a lint free shop towel. After this, you will have the minimum amount of old engine oil remaining.

I think you can safely forget about this visualisation of metal shards all though the bike. If there is any, the strainer, the filter, the plug magnet, and the stator magnets will take care of that.

Anyway, large levels of pedanticism is not necessary changing engine oil. It is the pink blankie under its' bike cover approach, and serves only to make the rider feel better. But hey if it feels good - do it!

Steve

**Mom** · 24th March 2010, 06:26

Originally Posted by MaxB

Hot always, for reasons already mentioned.

Be an interesting time at work tomorrow esp. if you're a 'majority of 1'.

No there were a couple of us "hotties" but, there were also some "male know it all, get back in the kitchen" types who were absloutely right doing it cold.

**TimeOut** · 24th March 2010, 06:36

Defiantly hot, it gets all the other crud suspended in the oil. But I try to let it drain overnight to get it all the oil out (as Steve said)

If you change it cold some of the contaminates will settle to the bottom of the sump and stay there.

**Owl** · 24th March 2010, 06:37

Originally Posted by Mom

Right you bunch of smart, educated and intellegent bikers

Mom, are you sure KB was the right place for this thread?

**CookMySock** · 24th March 2010, 06:41

Originally Posted by TimeOut

If you change it cold some of the contaminates will settle to the bottom of the sump and stay there.

It is tempting to visualise this happening, but I am not persuaded. I would be interested in theories or practice on what solids may have bypassed the filtration methods mentioned, or what liquids there may be that have separated from the engine oil.

Steve

**scumdog** · 24th March 2010, 07:05

Originally Posted by TimeOut

Defiantly hot, it gets all the other crud suspended in the oil. But I try to let it drain overnight to get it all the oil out (as Steve said)

If you change it cold some of the contaminates will settle to the bottom of the sump and stay there.

Hot or cold (mostly cold) and I leave it overnight as above.

**T.W.R** · 24th March 2010, 07:12

Originally Posted by DangerousBastard

I would be interested in theories or practice on what solids may have bypassed the filtration methods mentioned, or what liquids there may be that have separated from the engine oil.

Steve

You'd be surprised what settles in the sump of a motor, especially in older engines........swarf, sludge, gasket particles, sealant etc
Motorcyle engine oil pumps don't operate at especially high pressures and the majority of internal oil galleries aren't large so bigger particles just end up collecting in the bottom end

Even with draining oil hot and leaving to drain for a period of time it's always worthwhile flushing with a small amount of fresh oil too before refilling