Product Description

Mobil Pegasus™ 605 is a high performance natural gas engine oil primarily intended for the lubrication of modern medium and high-speed four-cycle engines operating on fuel that contains corrosive materials such as hydrogen sulphide or halogens (compounds containing chlorine, fluorine, etc.). These engines are generally of the lean-burn design where increased manifold pressures prevent sufficient lubricant from reaching the valve guide areas resulting in low oil consumption which can lead to valve guide wear and valve recession. This effect also increases the potential for wear and acid attack of upper cylinder components from the corrosive materials generated during combustion. The Mobil Pegasus 605 is a 0.5% ash gas engine oil with exceptional reserve alkalinity designed to offset the negative effects of acidic materials on engine components. The excellent corrosion protection properties helps prevent corrosive wear in cylinders, valve areas and bearings which can result in longer engine life and lower maintenance costs. Mobil Pegasus 605 provides excellent anti-wear and anti-scuff performance which helps assure minimal piston scuffing, scoring and low cylinder liner and piston ring wear. This oil can also be used for the lubrication of the reciprocating compressors in landfill and biomas gas applications.

Mobil Pegasus 605 is formulated from high quality mineral base oils combined with an advanced technology, low ash additive system designed to provide excellent protection of engine and compressor components. This product exhibits a high level of chemical stability and resistance to oxidation and nitration. Pegasus 605 offers outstanding resistance to valve train wear and protection against deposit formation. These performance advantages combined with the very effective detergency and dispersancy characteristics helps control the formation of ash and carbon deposits that could result in poor engine performance and detonation. This product also compatible for use in gas engines equipped with catalytic converters.

Features and Benefits

Mobil Pegasus 605 Gas Engine Oil provides an additional margin of protection in those applications using contaminated fuel. Its excellent detergent / dispersant technology also results in cleaner engines, lower wear rates and improved engine performance. The use of this product can result in reduced maintenance costs and improved production capacity. Its excellent chemical and oxidation stability can result in longer drain periods and reduced filter costs. The high reserve alkalinity of this product allows its use in engines operating on fuels with low to moderate amounts of corrosive materials in the fuel gas.

Features Advantages and Potential Benefits
Optimised TBN and Reserve Alkalinity Controls wear and corrosion when using contaminated gas

Protects valve seats and faces on four-cycle engines

Controls combustion chamber ash formation and improves spark plug performance

Outstanding Anti-wear and Anti-scuff Properties Lower wear of engine components

Reduced scuffing of liners in highly loaded gas engines

Provides excellent break-in protection

Excellent Oxidation and Chemical Stability Cleaner engines

Extended drain intervals

Reduced filter costs

Excellent resistance to oxidation and nitration

Effective Corrosion Resistance Reduces valve guide wear in four-cycle gas engines

Protects bearings and internal components

Exceptional Detergent / Dispersant Properties Neutralises formation of acids in the oil

Protection of upper cylinder and valve train components

Cleaner engines

Longer filter life

Non-zinc and Non-phosphorus Formulation Improves catalytic converter performance and longer life


Note: Engines operating on fuel gas with elevated levels of sulphur or halogens should also have coolant (jacket water) and oil temperatures raised.

• Gas engines operating on fuel that contains moderate levels of hydrogen sulphide (H2S)

• Engines operating on fuel containing other corrosive materials such as TOHCl (Total Organic Halides as Chloride) such as landfill or biomas gas

• Spark ignited four-cycle gas engines with very low lube oil consumption

• Medium and high speed four-cycle engines equipped with catalytic converters requiring a low ash gas engine oil

• Engines experiencing valve train wear and corrosion

• Reciprocating compressors operating on natural gas that contains sulphur or chlorine compounds

• High output or naturally aspirated engines operating at or in excess of rated capacity under high temperatures

Specifications and Approvals

This product has the following approvals:
GE Waukesha Engine Landfill Gas Applications

Properties and Specifications

Grade SAE 40
Kinematic Viscosity @ 100 C, mm2/s, ASTM D445 13.2
Kinematic Viscosity @ 40 C, mm2/s, ASTM D445 124
Viscosity Index, ASTM D2270 100
Ash, Sulfated, mass%, ASTM D874 0.5
Total Base Number, mgKOH/g, ASTM D2896 7.1
Pour Point, °C, ASTM D97 -15
Flash Point, Cleveland Open Cup, °C, ASTM D92 262
Density 15.6 C, lb/gal, CALCULATED 0.890

Health and safety

Health and Safety recommendations for this product can be found on the Material Safety Data Sheet (MSDS) @


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.