Thoughts On A Cold Oil Change.

The reason we change oil is twofold I suspect
1) the oil degrades with use and provides less protective properties
2) build up of particulate matter within the oil.
If you drain a cold engine, the particulates not trapped in the filter will have settled towards the bottom of the sump/engine cases... the oil being less viscous than warm oil will tend to be harder to encourage from the base of the sump/engine cases and so the residue left in the engine will be more particle rich than that of a warm engine.
I have no proof of the above, but that’s how I picture the reasoning in my mind... whether the particles do actually “settle” and therefore significantly contaminate the fresh oil, I don’t really know, I just imagine

 

3 reasons for a hot oil change over cold:
One has been mentioned above with regard to contaminates in the oil being flushed out instead of settling out in the engine.

Hot oil will obviously drain quicker.

Also to be considered when changing the filter, even after priming a new filter there will be a slight delay in
pressure build up as the new oil is pumped round. As 90% of engine wear is reckoned to occur during cold starts do you really want to add to this with a cold oil & filter change? JMO

 

I agree hot oil is better to drain

 

I do think the last point is the most pertinent one. This is why I have long used 0W-20 in cars when the 5W and 10W was an option. Those cold starts.

 

The short answer is that it does not make a blind bit of difference.

The cold engine was hot when the oil drained into the sump therefore the sump is the only area of interest in a cold change. Hot oil flows more readily but the issue then is time. How patient are you waiting for the last drip? The only theoretical basis for a hot change over a cold is that fewer suspended solids will have sunk to the bottom of the sump and be more readily flushed. In practice most bikes are so mollycoddled their oil is not some thick gloop and is quite lightweight anyway. Any residue left on horizontal surfaces is massively diluted by new oil.

I mostly change oil cold to avoid burnt hands and unnecessary spills. The microscopic difference of a hot sump floor does not keep me up at night.

 

Ermmmmmm ..... why not drain it when hot AND let it drain overnight? Best of both worlds/theories?

 

Why not remove the sump plug when cold start her up and warm the oil as it drains.?




That’s not helpful is it?

 

I also dont think it make a difference and i have done plenty of cold oil changes on some engines you may find that changing oil hot will result in less oil needed to replace as the suspended oil in galleries etc may not have had time to drain completely.
As for particulate matter if gathers in the sump the design should be as such that the oil pick up should never be low enough to actually draw settled metal into the pump and any microscopic particles will be caught by the filter anyway.

I always use a pump on my car as i cant be bothered to jack it up and get underneath these days and in country's like Japan and the US this is done most of the time.

 

Most cars put the filter near the drain plug under the car, usually recessed. How does the pump method get access to a filter without lifting? I had a Subaru where this wasn’t hard, but all the other cars I’ve driven lacked ground clearance to reach a filter.

 

I think you have misunderstood.....In my experience most cars have the oil filter somewhere on the block as its always on the pressure side of the pump, if your referring to the pick up for the pump its usually has a baffle around it to prevent debris from ending up near it to stop the pump picking up anything and often nowhere near the drain plug.

 

I've started changing my oil cold - more for convenience than anything else as I'm not always wanting to go for a 10 mile drive just to do an oil change.
In theory, any contaminants are likely to have settled and won't be held in suspension as they would in warm oil and could in theory form a silt-like layer on the bottom of the sump but the flow of oil out of the drain is likely to take most of this with it and also, I use a magnetic sump plug which has a neodymium magnet and seems to attract no more than a grape-pip sized amount of sludge anyway and so we're talking tiny levels of crud, if any at all.
Modern oils are so runny these days that I find it better to drain cold as it avoids spills.
Another thought on this - prior to installing the magnetic drainplug, I replaced the stator cover in my 15000 mile 1050 following a dropped bike incident. I noted the stator magnet is very large and powerful - indeed, as it is bathed in engine oil, surely the ultimate magnetic sump plug!!!??? With this in mind, I gave it a good wipe down before reassembling the stator engine cover and there was not one molecule of metallic swarf stuck to it. As it is downstream of the oil filter, one can only assume the crap that is normally picked up by the magnetic sump plug would otherwise be stopped by the filter anyway or similar deposits would be found on the stator magnet and . . . they're not. Me thinks the amount of particulate crud remainining in the sump after a cold change is therefore next to zero!!!!

 

On the Z I have a neodymium magnet clamped to the side of the oil filter so any metallic particles small enough to pass through the filter just stick to one side of the filter can.
I fitted the magnet from new and opened up the filter at the 500m change and you could see what looked like very fine metallic paint stuck to the side of the filter can. You could argue that any particles small enough to pass through a decent filter wouldn't harm the engine anyway. IMO the 3 golden rules are decent oil, decent filter and regular changes. "Regular changes" is open to interpretation. The change interval on the SS is 10k but I'll be changing it long before then.

 

Draining oil when hot or cold makes no difference if leaving to drain overnight, fitting a magnetic sump plug can catch metallic particles, these sump plugs are cheap to buy. When an engine is running microscopic particles from bearings etc are caught in the oil, this is especially true during the running in period, the idea of "you don't need to run in modern bikes and cars" is crazy, during the running in period metal from contact areas (including gearboxes) remove microscopic particles of metal,this in turn then reduces internal friction and losens up the engine, in turn it will run smother and use less oil and be more efficient.

 

I've never run a four stroke engine in the old saying was thrash it from new (and under warranty) always buy the demonstrator they're quicker ie not run in

 

Best of luck returning such a bike under warranty with an engine that's been abused, (and yes you can tell upon inspection) a number of dealers use their staff to run the demo bikes in for a number of miles before letting the public out on them. Personally I don't pay my hard earned cash on new bikes to abuse them, but everyone to their own. I've stripped many engines in the past and know if one has been abused or not. Dealers are canny folk, they know their demo bikes are going to get abused by a minority of people on test rides, go to your local dealer and ask if you can take a zero mile machine for a test ride and wait for a quick no answer. A local guy to me thrashed his brand new GSXR from the word go, it got a nasty rattle, returning it to his dealer and after a strip down guess what no fix under warranty, a later court case went in the dealers favour. It's a sobering thought.

 

Remember the old "running in please pass" stickers/signs they used to display bit like the old "owned by little old lady and only used on a Sunday for church" so the fist time you give it some beans it seizes up there are ways to run in a motor.