what oil to use?

[Thorby]

james1963 wrote

my father has a 1971 CB 750 k and he's always used 20w 50 caster oil motorcycle, cause of the heat they put out, and he said stopping and waiting at red lights they build up a lot of heat and the heavier oil keeps the motor cooler at all times ,but in winter months takes a little more cranking cause of the thickness,

I wouldn't use castor oil.

Kidding.  I've used regular Castrol high mileage without issue.  My bike desperately needs a change so I might go with that again.

Some say it creates gunk, so I may stick with it or use Valvoline.

[Re-run]

Generally, unless you already have a leak or crappy seals, a high mileage isn't really needed. I don't think there is any more build up than typical oil though. If you have the very common left side head leak, which is a low pressure side, you could try it but I don't know if it would improve any.

I think it is more important to just use an oil that covers your heat range, and then change it as needed. Lots of cb engines make 100,000 miles before needing any "real" work.

[Lincoln Highway Bullitt]

I use Brad Penn "the green oil". It has the high levels of zinc that the oil companies have taken out. Camshafts need the zinc.

[Re-run]

The zddp, which is what you are refering to, is a "last line of defense" additive. It only comes into play when the oil film gets broken down. If that starts to happen, more than cam damage will occur. In old engines, the cb engines doesn't really qualify, flat tappets needed the zinc, especially on break-in. Mainly because of spring pressures.

But, for future reference, rotella t6 5-40 has 1200ppm zddp. Pretty equivalent to brad penn, and probably cheaper. It is also jaso 2 certified.

But, as I said before, use what works for you. If you get the results you want, then you aren't doing anything wrong.

[LukeM]

I've run Rotella T6 5W-40 in my 84 Shadow for the last 2 years.  It does clatter a bit more than usual on initial start and until the engine warms all the way up.  I may see if there's an equivalent oil that is like a 15W-50 or something.  I worry about driveline wear with such a thin oil.

PS:  my Shadow has hydraulic valve adjusters (no shims or manual adjustments), your CB750 situation will probably be different.

Luke M