LUBRICATING OILS

Written by Peter Ballard  MIMechE.

Technical Adviser Cossack Owners Club

Part 1

There is still much confusion and misinformation out there over the best lubricating oils to use in our engines, gearboxes and final drives. I have taken advice again from oil companies and companies that supply the vintage motorcycle owners and rac­ers. I am concerned about getting the best protection available, as opposed to the cheapest or easiest. Here is my considered advice:

Final drives or differentials.

Hypoid or EP 90. An alternative can be a Hypoid or EP 140 in summer or if the unit is warn and you wish to quieten the whine before eventual rebuild.

Multigrades - a 90/140-gear oil is suitable.

Gearbox:

Urals - summer Hypoid or EP 90. This gives quieter gear changes than 80 grade but causes more drag. If you have really delicate feet and manage quiet gear changes use Hypoid or EP Light 80. In winter change to EP Light 80, if you use the bike for short journeys in cold weather.

Dnieper boxes (4 speed and reverse type). Same grade as above, but do not use EP grade. There is a risk that the additives in EP (Extreme Pressure) lubricants will damage by corrosion the brass bushes on the output gears and cause premature failure.

Multigrade gear oils - a 75/90 will replace a 80 or possibly 90.

Multigrade engine oils (eg 20W/50) - will offer satisfactory protection; but not as good as purpose designed gear oils.

Two strokes with multi-plate clutches in the gearbox - Hypoid Light 80. If you use a 90 grade then the clutch may drag or slip a little when first used from cold, but the gear changes will be quieter, probably good for hot weather use.

Engines:

Dnieper plain big end bearing engines (K650, MT9. MT10, MT11, MT16, MT19 and similar).

Use a good quality Multigrade 20W/50 from a reputable oil company all year round.

Urals and Dnieper MT12 with roller big ends. As per the original BMW engines, use a Straight or Monograde 40 all year. Possibly use 30 grade in winter if the bike is kept outside and the engine never really gets warm in use, otherwise keep to 40 grade. Multigrades? Until recently it was not advised to use any multigrades in these engines to get the best protection.

Multigrades:

Ø   Good - they do not thin at high temperatures as much as mono grades and thus maintain viscosity.

Ø   Good - they do not thicken at low temperatures as much as mono grades and thus help starting by reducing the load on starter motors or leg.

Ø   Bad - the additives (long change polymers) to achieve viscosity control over wide temperature range tend to get destroyed in an air-cooled engine with local hot spots and reduce their protection quicker than in a water-cooled car engine.

Ø   Bad - they contain additives to minimise stiction and also shear very easily which is ideal for the shell bearing car engines they were designed for. The rotational speed of a big end on its crank pin is not constant during a single constant speed crankshaft revolution (think about that over a pint!). Thus the big end rollers need to speed up and slow down twice each revolution. To do this they need to gain traction from the crank pin and the inside of the conrod. The use of oil that is designed m help things slide (like a modern multigrade) is unhelpful, since the rollers will tend to slide and can cause the oil film to fail locally at big end roller contact resulting in increased wear. The use of a lubricant that allows the rollers to roll instead of sliding, such as a monograde oil with no shear viscosity reduction additives will increase the life of the big ends.­

Oil Change Frequency.

Keep to the manufacturers' recommendations, particularly during running in and the warranty period read the manual.

Synthetic oils typically last up to twice the mileage as mineral based oils before needing changing.

If you use your bike for short journeys and it often gets very hot in traffic, then change the oil more frequently.

If you use your bike for long gentle runs, then the engine oil will degrade slower.

Changing the oil more often than needed is a waste of money and a waste of oil and does not extend engine life.

Some General Comments:

Ø   The most expensive lubricating oil is not necessarily the best for your machine, grade and type is far more important.

Ø   Engine oils are designed to work in engines and gear oils are designed to work in gearboxes, so do not use engine oils in gearboxes since gear oils are better.

Ø   Lubricating oils contain a vast range of additives to control corrosion, to dissolve deposits, to reduce stiction, to change viscosity in a predictable manner with changes in temperature, to cope with local high temperatures without degrading and much more, they are not just refined crude oil.

Ø   The blackness in the oil after use is partly due to combustion products getting past the piston rings, but also due to degrading and burning of the lubricating oil and its additives resulting in what is called ash.

Ø   Detergent content. All multigrades contain significant detergent. Monogrades can be obtained with or without detergent content. The detergent is there to keep the engine clean and then keep the deposits in the oil until the oil is changed. If the engine has not been run on detergent oils before and has not been stripped and cleaned recently, then there is a risk that the detergent content of a lubricant containing detergent will loosen the old deposits and circulate them around the engine; which is not good with an engine with no or poor filter fitted.

Ø   Typically the base oil for a lubricant is mineral oil (from the ground) or vegetable oil (typically caster or even olive oil). Synthetic lubricating oils are synthesised from various chemicals to meet high performance requirements, they last longer than mineral oils before degrading and tend to reduce engine oil consumption. It is probably a waste of money to use a synthetic oil and change it at the same periods as a mineral based oil, you are not getting the extended life benefit you paid for. The manufacturers of our bikes do not quote oil change periods for synthetic engine oil, but they tend to last up to twice as long before needing to be changed.

Ø   The higher the number on the SAE scale the more viscous (thicker) is the oil.

Ø   Engine oil grades are measured on a different scale from gearbox oils. Thus a certain grade engine oil is more viscous than a similar grade gear oil at the same temperature. This is to account for engine oils have a higher normal operating temperature than gear oils.

Ø   Multigrade 20W/50. This means that the oil is behaving like a 20 grade at -18^°C (W denoting Winter) and like a 50 grade at 100^°C. Under the typical range of engine operating conditions, a mono grade 40 is generally thicker than a 20W/50.

Ø   Many Japanese engines use roller bearing big ends and yet recommend multigrades! The multigrades will aid electric starting at low temperatures on these engines. The engines were designed with multigrades in mind and have a very long design life anyway where big end failure will not be expected before wear of other components.

Last but not least.

Dispose of waste oil at a recognised recycling centre or disposal centre. Telephone your local council for the location of such a site.

 Engine Oil recommendations direct from the Lubricant Manufacturers Applicable to the Ural and similar engines with roller bearing `big-ends'. (Including Ural M63, M66, M67,IMZ series, M72, K750, MTi2 )

Notes from PJB:

Miller Oils offer no explanation as to why they think their multigrade is more suitable than their monograde SAE 40, even with a direct request for an explanation.

If on a trip away from home, you run low on engine oil, and you cannot get any monograde oil; then good quality 20Wi50 engine oil can be used to top up.

Multigrade oils in these engines will not give as good wear protection to the roller big ends as the above-recommended oils, but they will protect everything else well. Extra wear of big ends due to occasional use of multigrades under moderate use will be undetectable,

Dnieper overhead valve engines (K650, MT9, MT 10, MT10-36, MTI1 and MT16) which have shell bearing big-ends should use a multigrade 20W/50 engine oil from a reputable manufacturer for best protection all year round.

I am pleased to say that David Angel of 'F2 Motorcycles', a leading Ural dealer and long time Ural owner, has had more success than me and has the following comments and recommendations from other major lubricating oil companies.

I have no problems with these recommendations at all, except:

Ø   It does concern me that the lubricating oil companies Rock Oil and Mobil have given the COC directly certain recommendations and 'F2 Motorcycles' different recommendations. I do not believe either recommendation is necessarily wrong, but it is not very professional for these major companies to issue apparently conflicting -I' Morris Oils still recommend a conventional mineral oil based 20W/50 that apparently conflicts with all other recommendations so far.

With respect to the choice between one of the specifically recommended advanced fully synthetic oils or a medium to high detergent mineral or vegetable based mono grade then I offer the following advice:

Ø   If you intend to use your Ural in extreme conditions including frequent cold starts, short journeys, frequent stop-start city driving especially in hot weather or in very cold environments then fully synthetic multigrade engine oil is likely to give the very best protection.

Ø   If you intend to use your Ural for less arduous service such as Sunday runs out, long runs to rallies, no short trips i.e. maybe the use typical for the days when 'Classic' motorcycles were 'modern' then a medium or high detergent monograde will give good protection.

I am pleased to forward David Angel's comments and the advice he has obtained from lubricating oil companies.

But please note the following:

Ø   If you have bought a new or second-hand motorcycle from a dealer and have a warranty on that machine, then you must use the oil and change intervals that the dealer recommends. If not your warranty may be invalidated.

Ø   All advice forwarded by myself and David Angle is consistent in that it is considered not advisable to use in a Ural a conventional mineral oil based 20W/50 multigrade whether bought from a super market or from a major oil company. Both the recommended straight oils and the recommended fully synthetics will be better