You won't completley drain every molecule of oil out when you drain it since these oils are still designed to cling but I doubt you would be leaving more than 1% of the total capacity after draining. The philosophy seems akin to "boundary Lubrication" where a thin layer one molecule thick sticks on the components. A simimlar principle occurs in synovial joints in Humans.

I stand to be corrected but although Castrol markets Magnatec as synthetic it's actually manufacted from fractionating mineral oil rather than manufacturing the olefins de novo in the lab.

Castrol Magnatec Professional’s intelligent molecules cling like a magnet, dramatically reducing* engine wear. Micro filtered and with its signature green colour its your guarantee of Professional quality. Up to 75% of engine wear happens while your engine warms up. When the engines tops, oils drain off critical engine parts, however Castrol Magnatec Professional’s intelligent molecules don’t. They cling to the engine like a magnet providing an extra layer of protection; ready to protect from the moment you turn the key.

Castrol Magnatec Professional has been specially engineered to deliver outstanding wear protection in today’s modern engines. Modern diesels are fitted with Diesel Particulate Filters to remove harmful particles from the exhaust. Castrol Magnatec Professional OE 5W-40 is specially formulated to protect them by preventing deposit build up. Castrol Magnatec Professional. Instant protection from the moment you turn the key.

You won't completley drain every molecule of oil out when you drain it since these oils are still designed to cling but I doubt you would be leaving more than 1% of the total capacity after draining. The philosophy seems akin to "boundary Lubrication" where a thin layer one molecule thick sticks on the components. A simimlar principle occurs in synovial joints in Humans.

I stand to be corrected but although Castrol markets Magnatec as synthetic it's actually manufacted from fractionating mineral oil rather than manufacturing the olefins de novo in the lab.

I think I've seen a figure of 20% for oil retained in an engine after draining, though it'll vary with the design.

I've seen it suggested that straight weight mineral oils resisted corrosion better in light aircraft engines (which are parked most of the time) because of less drain-down. I dunno if this is true.

Re "I stand to be corrected"...I think you can sit down.

Castrol started marketing extensively hydrocracked Group III oils as synthetic,

In 1999, Mobil (with a vested interest as the main producer of actual synthetic oils) filed a complaint with some US advertising standards outfit, which found in Castrol's favor.

So, since that precedent, in most markets synthetic doesn't necessarily mean actually synthesised from simple molecules, and usually doesn't,

I THINK this is true in The Yook.

In Germany I understand the term is legally restricted to actual synthetic oils, though I dunno if compliance is enforced.

xtremerevolution.net/a-defining-moment-for-synthet.../

So bicycles are not as green as they are made out to be if they use oil for their chains?

Who knew?

I must get some for my bicycle chain as I often freewheel down hills.

Forklift chain spray is very good for cycle & motorcycle chains due to its non fling formulation, a few of my friends exchange a pint of beer in return for a can of chain spray.