Two-Stroke Diesel Engine System Oil

Mobilgard 300 C is a premium quality system oil specially formulated to provide superior engine cleanliness, better wear protection and longer oil life when compared with conventional system oils. It is designed for use in two-stroke, crosshead marine diesel engines operating under severe conditions. This product has sufficient alkalinity to protect against strong acids which may find their way into the crankcase from the combustion of fuel sulphur, and it has enhanced load carrying ability in order to reduce wear in heavily loaded bearings and gears.

Features and Benefits

The high quality paraffinic base oils used in Mobilgard 300 C have excellent thermal stability and oxidation resistance. The formulation includes proprietary detergent and anti-wear additive systems to deliver enhanced crankcase cleanliness, along with excellent protection for highly-loaded engine parts. Mobilgard 300 C also provides good rust protection in case of water contamination, and excellent water separation characteristics.
When used as recommended in crosshead type diesel engines, Mobilgard 300 C system oil offers the following features and potential benefits:

Features Advantages and Potential Benefits
Enhanced detergency  and improved thermal and oxidation stability Reduced deposits in piston cooling spaces
Better piston cooling efficiency
Cleaner crankcases and circulation tanks 
Enhanced load-carrying and anti-wear performance Excellent protection for highly loaded engine components such as bearings and gears
Excellent rust and corrosion properties Longer bearing life
Protects critical bearing surfaces
Good water tolerance and separation capability Effective lubrication in the presence of water
Longer oil life due to efficient water separation


Mobilgard 300 C is recommended primarily for use as system oil in late model, high-output, crosshead diesel engines, especially those engines employing the system oil for piston cooling. It will prevent or reduce deposit formation in the piston cooling spaces, thus maintaining piston cooling efficiency and reducing the incidence of piston top burning and piston crown cracking. It will also prevent or reduce crankcase deposits and will provide outstanding protection for heavily loaded bearings and gears. Good rust prevention and water separation characteristics make Mobilgard 300 C an excellent system oil in older design crosshead diesel engines which have water-cooled pistons and where crankcase deposits can be a problem with lower-quality system oils.

Typical Properties

SAE Grade 30
Specific Gravity at 15ºC 0.8665
Flash Point, ºC, ASTM D 92 245
Pour Point, ºC, ASTM D 97 -24
Viscosity, ASTM D 445  
cSt, at 40ºC 109
cSt, at 100ºC 11.9
Viscosity Index, ASTM D 2270 98
TBN, mg KOH/g, ASTM D 2896 9
Sulphated Ash, wt%, ASTM D 874 1.06
FZG Scuffing, Fail Load Stage, A/8.3/90, ISO 14635-1 12

Health and Safety

Based on available information, this product is not expected to produce adverse effects on health when used for the intended application and the recommendations provided in the Material Safety Data Sheet (MSDS) are followed. MSDS’s are available upon request through your sales contract office, or via the Internet. This product should not be used for purposes other than its intended use. If disposing of used product, take care to protect the environment.


It cannot be guaranteed that the product information given above is up to date. For the latest version of the Product Data Sheet we refer to the product library of ExxonMobil.