1946 Model 18 oils

Not in the primary. for that you need thin monograde. Otherwise you will have as many clutch issues as me!. Farming supplies stock 20 .

Previously stephen_roberts wrote:

Thanks Robert, should i use an oil with detergent for the engine?

The motor does not have an effective filter to collect the crud that detergent oil will pick up. I would use a low detergent oil .

SAE 40 would be a better oil for all year use, especially in a cooling climate. I even top mine up with SAE 30 at the back end.

You can buy SEA 20 for your primary, I think Millers are one supplier.

80/90 for your gearbox, I use Castrol EP90 but make sure it is the classic version.

Not sure about detergent. The only bike I use detergent oil is in my Commando with a spin on / off filter.

Previously stephen_roberts wrote:

Thanks Robert, should i use an oil with detergent for the engine?

The jobs of the detergents are to keep hot surfaces, like piston grooves and lands. clean and to neutralize the acidic products of combustion.

Dispersants stop the sludge and soot from agglomerating into larger lumps which block oilways and cause increased wear levels..

Both of the above are good ideas, so I see no reason not to use a modern multigrade , 15W40 or 20W50 oil in your engine, and benefit from their higher levels of detergents and dispersants,. I would use a good flushing oil first.

Nothing like an oil thread to get a lively debate going!. These old singles usually have large clearances and plenty of oil leaks with engine oil migrating into the primary through feeble sealing arangements, plus wet sumping and roller/ball bearings throughout.I don't think Multigrade oils are ideal with these issues.

The non detergent oils drop any crud they pick up quickly, most likely in the oil tank as the oil is not moving allowing it to settle, which is why on every oil change you should clean the bottom of your tank if using non detergent oils. A detergent oil will hang on to the crud in the expectation a filter will remove it, no filter and it carries on circulating. I would fit a filter regardless of what oil I was using but using detergent oils makes it mandatory.

I do think a filter is a good thing,but in my book if it looks horrible or blocks access to important areas or is vulnerable to impact then I would not bother. My 99 is still running the orriginal std crank, cam etc, with no filter,I would value regular oil changes ,magnets in sump and tank and an air filter before an oil filter, But I can see that as values climb it makes sense to protect your investment.Roller big ends are not cheap or easy to replace.If you intend to continue to use a servicable high milage piston and rings (and why not?) then detergent oils may well give you a smokey engine when they dissolve the ring of carbon on the piston lands and grooves.

Charles Bovington probably knows more about lubricants than any other club member. Personally, I would place more confidence in his opinions, than in those of unqualified "experts".

Regarding the removal of carbon, from piston rings, surely this can only be of benefit, since it will allow the rings to perform their designed function.

John, without doubt, Charles is a lubrication expert but please don't write off the many riders who base their responses on years and a lot of miles of their experiences.

I remember once using a fuel system cleaner (RedX) on a high mileage engine, thinking I was doing the right thing? What a racket after doing that.

It's a forum, not a home for qualified experts only.

O.K. Neil, using RedX on a high mileage engine may have caused problems (but, probably revealed an overhaul was overdue!).

Since the majority (not all) of modern motorcyclists cover quite low mileages, an annual oil change would be a small proportion of their running costs. Providing different brands are not mixed, a 20/50 oil should be quite good enough for normal use.