Mobilgard 300

Mobilgard 300

Diesel Engine System Oil

Mobilgard 300 by ExxonMobil is a premium quality, extra high performance system oil designed for crosshead diesel engines. High quality paraffinic base oils along with a balanced additive system provide excellent protection even for the severe operating conditions of the latest design, high-output crosshead marine diesel engines. This product has sufficient alkalinity to neutralise any 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.

Features and Benefits

Mobilgard 300 is formulated from high quality paraffinic base oils that have excellent thermal stability and oxidation resistance. These base oil characteristics are augmented with a balanced additive system that includes special high temperature oxidation inhibitors, alkaline detergents, a load carrying component and defoamant. The formulation has maximum antiwear properties, good rust protection in the presence of salt water, and excellent water separation characteristics.

When used as recommended in crosshead type diesel engines, Mobilgard 300 system oil offers the following features and potential benefits:

Features Advantages and Potential Benefits
Improved thermal and oxidation stability Reduced deposits in piston cooling spaces and crankcase
Better piston cooling efficiency
Enhanced detergency Cleaner crankcases and circulation tanks
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 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. Its reserve alkalinity allows for the burning of high sulphur fuel. Good rust prevention and water separation characteristics make Mobilgard 300 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 0.889
Flash Point, ºC, ASTM D 92 266
Pour Point, ºC, ASTM D 97 -12
Viscosity, ASTM D 445  
cSt, at 40ºC 111
cSt, at 100ºC 12
Viscosity Index, ASTM D 2270 97
TBN, mg KOH/g, ASTM D 2896 5
Sulphated Ash, wt%, ASTM D 874 0.73


Health and Safety

Based on available information, this product is not expected to produce adverse effects on health when used for the intended application, following the recommendations provided in the Material Safety Data Sheet (MSDS). MSDSs are available upon request through your sales contract office, or via the Internet on 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.