20/50

[Seamus]

Still have about a litre of R for adding to fuel. Confuses people when I turn up on the 500

[philward]

The Duckhams Oil Company were the inventors of the 20W50 multigrade oil which meant that motorist now didn't have to use a different oils according to the temperature or time of the year. This blend of oils was a revelation to the British automotive industry as it went a good deal of the way to compensate for the less than exact engineering tolerences and practices of the day. Your average 15 year old Morris Minor or brand new Triumph now sounded quieter for longer. (Still leaked though!) Then along came the Japanese with their clever metric measuring stuff and brand new machinery that didn't require Old Harrys' skills to compensate for clapped out 60 year old bits of kit. New machine tools meant the Japanese could consistantly work to tighter tolerences which naturally allowed for the use of thinner lubricants, hence the switch to grades such as 10W40. A thinner oil equals faster warm up and so less wear from cold start up; less stiction in moving parts so they can be made to move faster and lighter and cheaper. Thicker engine oil was no longer the way to go so the evocative odour of Castrol R became a faded memory where bikers gathered, and a jolly good thing that was too for any motorcycle engine rebuilder.

All this is just my version of the oil question as I hadn't previously come across anyone regularly using or advocating the use of 20W50 oil in any Japanese bike since the 1970's. Obviously there are some that did and still do and if that works for them, excellent, do what works best for you, I say.

Well put! A logical and pragmatic appraisal of the evolution of oil and bikes. On Jap bikes, the key is having good oil in the sump as opposed to the slight differences in grades. Modern semi or fully synthetic oil are the only issue that can affect the clutch plates due to the improved reduction in friction.

[davefirestorm]

My understanding is that an old engine ( I’m talking old Brit ) has “bits/film” of crud stuck to it’s innards and using modern semi/full synthetic oils can loosen this crud via the additives/detergent in it.Would this apply to our SOHC fours?

[Nurse Julie]

My understanding is that an old engine ( I’m talking old Brit ) has “bits/film” of crud stuck to it’s innards and using modern semi/full synthetic oils can loosen this crud via the additives/detergent in it.Would this apply to our SOHC fours?

That's a risk with any old engine that has been poorly maintained regardless of what oil is used. On our SOHC/4's, it is debris going around the engine, coming up the oil ways and blocking the oil restrictor jets that causes oil starvation to the cam and the result is catastrophic and very expensive to repair damage. It is the frequency of oil changes throughout an engines life that contributes towards mechanical and engineering longevity. It doesn't matter what oil it is as long as its changed regularly. Mineral for running in a newly built engine then on to semi synthetic. Never synthetic.

[davefirestorm]

My understanding is that an old engine ( I’m talking old Brit ) has “bits/film” of crud stuck to it’s innards and using modern semi/full synthetic oils can loosen this crud via the additives/detergent in it.Would this apply to our SOHC fours?

That's a risk with any old engine that has been poorly maintained regardless of what oil is used. On our SOHC/4's, it is debris going around the engine, coming up the oil ways and blocking the oil restrictor jets that causes oil starvation to the cam and the result is catastrophic and very expensive to repair damage. It is the frequency of oil changes throughout an engines life that contributes towards mechanical and engineering longevity. It doesn't matter what oil it is as long as its changed regularly. Mineral for running in a newly built engine then on to semi synthetic. Never synthetic.

Being a lifelong tight wad I would never use synthetic oil,did once on a VFR but then used semi synthetic on all modern bikes.I stick religiously to oil change frequency,always have 

[Nurse Julie]

My understanding is that an old engine ( I’m talking old Brit ) has “bits/film” of crud stuck to it’s innards and using modern semi/full synthetic oils can loosen this crud via the additives/detergent in it.Would this apply to our SOHC fours?

That's a risk with any old engine that has been poorly maintained regardless of what oil is used. On our SOHC/4's, it is debris going around the engine, coming up the oil ways and blocking the oil restrictor jets that causes oil starvation to the cam and the result is catastrophic and very expensive to repair damage. It is the frequency of oil changes throughout an engines life that contributes towards mechanical and engineering longevity. It doesn't matter what oil it is as long as its changed regularly. Mineral for running in a newly built engine then on to semi synthetic. Never synthetic.

Being a lifelong tight wad I would never use synthetic oil,did once on a VFR but then used semi synthetic on all modern bikes.I stick religiously to oil change frequency,always have 

Not a tight wad Dave.... just sensible by the sounds of it 😊😊😊

[Horace]

 Never synthetic.

May I ask why? A completely rebuilt motor is effectively a new one and unless the various seals are affected by it why not use it?

I was always a Duckams 20/50 user, peer influence probably. Currently I'm using Halfords Classic 20/50 in a cb750 and a cb77.

[Nurse Julie]

 Never synthetic.

May I ask why? A completely rebuilt motor is effectively a new one and unless the various seals are affected by it why not use it?

I was always a Duckams 20/50 user, peer influence probably. Currently I'm using Halfords Classic 20/50 in a cb750 and a cb77.

So a 1960's / 70's newly rebuilt engine would never have had fully synthetic used anyway. Also, any bike, in this case Honda SOHC/4' with the wet clutch system, which they all have except the CB750/4's, the clutch will slip more than a slippery thing. Semi synthetic is fine as is mineral.

[Rob62]

10w40 semi synthetic motorcycle oil for me, in all my classic bikes. I think 20w50 is too viscous for a bike engine.... no point in using fully synthetic unless you have the latest superbike in which case it will be correctly specified in the service manual.