Before creating the Vanabode travel style I ran a motorcoach website. This page is one of many bus articles I wrote for coach buyers before closing that website.

Detroit Diesel Allison Lube Oil Recommendations for Detroit Diesel 2-Cycle Engines

This information is VERY important for anyone purchasing any bus with a Two Cycle Detroit Diesel Engine - from DDC publication 6SA314 8901

Lubricant Recommendation
Detroit Diesel Two Cycle Engines

SAE Viscosity Grade 40 API Classification: CD-II, (Note: CD-II is an obsolete designation replaced by the current API Rating CF-2) Military Spec: MIL-L-2104D Sulfated Ash: Less than 1.0% - This is the only engine oil recommended for Detroit Diesel two-cycle engines. Lubricants meeting these criteria have provided maximum engine life when used in conjunction with recommended oil drain and filter maintenance schedules.

(For additional oil selection criteria, see publication 7SE270.) The API category CD-II (CF-2)(Note: CD-II is an obsolete designation
replaced by the current API Rating CF-2) is relatively new and may not be fully in use at the time of this publication. (NOTE: This publication was published in
1989) API category CD may be used provided the recommended military specification is satisfied.

Oils with API designation "CE" are not recommended in DDC two-cycle engines unless accompanied by CD-II (CF-2) (Note: CD-II is an obsolete designation replaced by the current API Rating CF-2)

Single Grade-High Ash Content Lube Oils

High ash oils (greater than 1,000 mass % ASTM D-874) tend to form excessive deposits on engine parts, resulting in impairment of their function (exhaust valve closure, for example). These are NOT recommended, except where the continuous use of high sulfur content diesel fuels (greater than 0.5 mass %) is unavoidable and where a high TBN, LOW ASH oil is not available.

Multi-Vis Oils

Less than optimum engine life must be expected when using 15w-40 oils. Multi-vis oils tend to break down due to mechanical and thermal stress which results in a loss of viscosity and premature engine wear. Multi-vis oils do help cranking when temperatures are below 32 degrees F (0 degrees C). However, once the engine starts, the major advantage of the multi-vis oils is exhausted. When the engine reaches operating temperature, the internal engine temperatures and pressures vary little from an engine operating in much warmer climates. This is when the 2 cycle engine benefits from the superior protection of a 40 wt.

Starting aids such as automatic ether systems and /or on-board auxiliary heaters provide more reliable starting without sacrificing engine life.

Function of Lubricating Oils

All diesel engines require heavy duty lubricating oils. Basic requirements of such oils are: Lubricating quality, High heat resistance, Control of contaminants, Lubricating Quality.

The reduction of friction and wear by maintaining an oil film between moving parts is the primary requisite of a lubricant. Film thickness and its ability to prevent metal-to-metal contact of moving parts is related to oil viscosity. The optimums for Detroit Diesel two-cycle engines are SAE 40 grade oils.

High Heat Resistance

Temperature is the most important factor in determining the rate at which deterioration or oxidation of the lubricating oil will occur. The oil should have adequate thermal stability at elevated temperatures, thereby precluding formation of harmful carbonaceous and/or ash deposits.

Control of Contaminants

The piston and compression rings must ride on a film of oil to minimize wear and prevent cylinder seizure. At normal rates of consumption, oil reaches a temperature zone at the upper part of the piston where rapid oxidation and carbonization can occur. In addition, as oil circulates through the engine, it is continuously contaminated by soot, acids, and water originating from combustion. Until they are exhausted, detergent and dispersant additives aid in keeping sludge and varnish from depositing on engine parts. But such additives in excessive quantities can result in detrimental ash deposits.

If abnormal ash deposits form on the exhaust valve seats, early engine failure may result. Oil that is carried up the cylinder liner wall is normally consumed during engine operation. The oil and additives leave carbonaceous and/or ash deposits when subjected to the elevated temperatures of the combustion chamber. The amount of deposits is influenced by the composition, additive content, engine temperature, and oil consumption rate.

Oil Quality

Oil quality is the responsibility of the oil supplier. (The term "oil supplier" is applicable to refiners, blenders, and re branders of petroleum products). Oil quality can also be affected by handling cleanliness, contamination, dirt, water, etc.

Engine Parts Can Tell The Difference in Oils

The following oil performance parameters should be compared:
Ring Sticking tendencies and/or ring conditions, piston skirt scuffing and cylinder liner wear and scuffing, exhaust valve face and seat deposits, piston pin and slipper bushing wear, overall valve train and bearing wear levels

Oil Caution

There are hundreds of commercial crankcase oils marketed today. Obviously, engine manufacturers or users cannot completely evaluate the numerous commercial oils. The selection of a suitable lubricant in consultation with a reliable oil supplier and observance of his oil drain recommendations (based on used oil samples analysis and experience), and provide filter maintenance, will provide the best assurance of satisfactory oil performance.

It should be noted that lube oil manufactures may reformulate and oil while maintaining the American Petroleum Institute classification, or may reformulate to a new API classification and continue the brand name designation. For example, SE oils being reformulated to SF letter code classification may perform differently after this reformulation. A close working relationship with the lube oil manufacturer should be maintained so that any reformulation can be reviewed and a decision made as to its effect on continued satisfactory performance.

Detroit Diesel Used Lube Oil Analysis Program

The Detroit Diesel lube oil analysis program is recommended for monitoring the condition of the crankcase oil in all engines. Primarily, used lube oil analyses indicate the condition of the oil but not necessarily the condition of the engine. Never tear down an engine based solely on the analysis results obtained from a single used oil sample. However, the condition of the engine should be investigated using conventional mechanical and/or electronic diagnostic instruments. Frequently, visual inspections are all that is required to detect problem areas related to engine wear. It is also prudent to obtain another oil sample from the suspected distressed unit for analysis.

Abnormal concentrations of some contaminants such as diesel fuel, coolant, road salt, or airborne dirt cannot be tolerated for prolonged periods. Their presence will be reflected in accelerated engine wear, which can result in less than optimum engine life. The oil should be changed immediately if any contamination is present in concentrations exceeding the warning limits.

Click for more information for Detroit Diesel engines from the official site.

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