E: Engine Oil Viscosity

[Bob]

I'm thinking about trying Royal Purple HPS oil. It is a synthetic oil with ZDDP added and is available in different viscosities. It could be good for our bikes but is rather expensive.

Royal Purple HPS High Performance Synthetic 10w40 Engine Motor Oil 6QT 5.676L

 

[greg brillus]

I don't believe any of these old engines benefit from synthetic oil, they are not high powered high tech engines by any means. Just change the oil and filter every year and don't use cheap K-mart oil. Oh and don't use a heavy oil either, unless you want the thing to be hard to start.

 

[poor1]

No one has mentioned either synthetic or fully synthetic. Always (for many years) used Millers and use fully synthetic multi grade diesel oil in petrol and diesel car engines without any problem and with the endorsement of the company. Any observations as regards the Vincent engines?.

 

[mercurycrest]

Just to throw a bit of debate into the pot.....

https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1049812

 

[stu spalding]

No one has mentioned either synthetic or fully synthetic. Always (for many years) used Millers and use fully synthetic multi grade diesel oil in petrol and diesel car engines without any problem and with the endorsement of the company. Any observations as regards the Vincent engines?.

Apparently, Harley Davidson vetoed the use of synthetic oil in engines with roller bearings as it promoted bearing skidding. Cheers, Stu.

 

[vibrac]

You old mineral guys will argue till the wells dry up

 

[macvette]

Apparently, Harley Davidson vetoed the use of synthetic oil in engines with roller bearings as it promoted bearing skidding. Cheers, Stu.

Harley recommends their own brand of synthetic oil for trans and motor. I have heard of roller bearings "skidding" but never found a definitive technical article. Is it a synthetic myth?

 

[BigEd]

Harley recommends their own brand of synthetic oil for trans and motor. I have heard of roller bearings "skidding" but never found a definitive technical article. Is it a synthetic myth?

"definitive technical article"
Macvette makes a good point here. Where does information come from? Is it a statement from a manufacturer, laboratory report, acknowledged expert, etc.
Information passed on from an "uncle of a friend's father's cousin who used to have a bike that never ran ....." should always be treated with suspicion and maybe a pinch of salt.

 

[Bowsh]

Hi All, I'm getting my first Vincent next week but now wondering what oil should I use. As my knowledge of oil only runs to virgin or sunflower.....

 

[greg brillus]

The best answer is from experience, I know of some who have run full synthetic in their Vincent, But why go to that expense......It's not like the parts are unavailable, and as many on this forum know, most bikes don't get enough use to actually ware them out. There is a very real possibility of the rollers skidding across the big end pin, I'm not sure I would take the risk. It is not worth the extra expense for synthetic in such an old designed engine, and there are too many people who take advice from expensive magazines who actively promote new and expensive products that are not necessary on these old machines. If you seriously think that running full synthetic in your Vincent will keep it going forever, well then use it........Like I said, you can't beat regular oil and filter changes, and don't use a heavy grade of oil.