The lubrication system is essential to prevent engine wear and allow smooth operation. There are several types of lubrication depending on the engine design and needs. The wet sump system uses an oil pump to draw oil from a sump and deliver it under pressure to bearings and moving parts through galleries and passages. A splash system relies on splashing to distribute oil from a sump to parts. A dry sump system uses a remote tank and additional pump for reliability in high performance or unusual operating conditions.

1. LUBRICATIONSYSTEM

2. Introduction
Lubricating circuit is one of the most important system in the engine. The engine cannot run
smoothly for a few minutes without lubricating oil.
▪ Dry or solid friction: when two metallic surface come in direct contact.
▪ Hydrodynamic or viscous or fluid friction: when two metallic surfaces are not in direct contact,
the only resistance to motion remains the resistance of the oil itself.
E.g.: Engine bearings and piston
▪ Greasy or boundary lubrication: lubricant is not sufficient to create separation of two surfaces,
only their high spots touch.
E.g.: piston rings and valve train
▪ Elasto-hydrodynamic lubrication: occurs under high loads, most commonly with high carbon
based oils. The pressure developed in the lubricant is sufficiently high to deform elastically the
metal surfaces on either side of oil film.
E.g.: engine valves and piston rings

3. PurposeofLubrication
• Reduce the frictional resistance of the engine to a minimum to ensure
maximum mechanical efficiency.
• Protect the engine against wear.
• Remove all impurities from the lubricated region by filtration.
• Form a seal between piston rings and the cylinder walls to prevent blow-
by.
• Serve as a cooling agent by picking up heat.
• Acts as good cushion against the shocks present in the engine.
• Helps to maintain an effective seal against the high pressure gases in the
cylinder.

4. Requirements of lubricants
• Viscosity
• Physical stability
• Chemical stability
• Resistance against corrosion
• Pour point
• Flash point
• Cleanliness
• Resistance against extreme pressure

5. Typesoflubricants
• Mineral oils – obtained from crude oil – greater chemical stability,
less tendency to form emulsions and abundantly available. Mixture
of paraffins, naphthenes, aromatics.
• Fatty oils – animal and vegetable oils, fish oil, linseed oil, olive oil,
etc..Animalsoils are not generallyusedasthey canburn.
• Synthetic oils – Silicon polymers , Silicon esters, Phosphate esters,
Fluorinated and chlorinated hydrocarbons – higher viscosity index,
reduced laquer formation, reduced loss due to vapourization, less oil

6. Automobile engine lubrication
The main parts of an engine which require lubrication are:
• Main crankshaft bearings
• Big end bearings
• Gudgeon pin bearings
• Piston rings and cylinder walls
• Timing gears
• Camshaft and camshaft bearings
• Valve mechanism
• Electrical equipment

7. Systems of Engine Lubrication
The various systems adopted for the lubrication of automobile engine :
• Petroil system: 2-stroke engines
• Wet sump lubrication system: 4-stroke small engines
• Splash system
• Pressure system
• Dry-sump system: 4-stroke

8. Petroil or Mist Lubrication system
• In two-stroke engines, the charge is compressed in the crankcase, and as such it is not suitable
to have the lubricating oil in the sump.
• Therefore for such engines lubrication oil is mixed with the petrol itself, the usual ratio being
2% to 3% of oil in the fuel tank itself. The oil and fuel mixture is inducted through the
carburetor.
• If it is less there is a danger of starvation or insufficient lubrication causing damage to the
engine
• However, if it is more there will be excessive carbon deposits in the cylinder head and the
engine will also give dark smoke.
• When the petrol enters the crankcase, due to high temperatures there, the petrol component
vaporises andthe oil, in the form of mist, goes into the cylinder through the crankcase.
• The oil that impinges the crankcase walls lubricates the crankcase, cylinder walls, crankshaft
and bearings.
• The main requirement of lubricating oil is it should readily mix with the petrol and burn
without leaving much residue.

9. Advantages
• Low cost as it does not require an oil pump, filter, etc.
• Simplicity in working

10. Disadvantages
• Releases heavy exhaust smoke due to burning of lubricating oil
• Forms deposit on piston crown and exhaust port which affect engine efficiency.
• Requires a thorough mixing for effective lubrication. This requires either separate
mixing prior to use or use of some additive to give the oil good mixing
characteristics.
• During closed throttle operation (as in the case of vehicle moving down the hill),
the engine suffers from insufficient lubrication as the supply of fuel is less. This is
an important limitation of system

11. • Used in light duty, slow speed engines (<250 rpm).
• Lubricating oil is stored at the bottom of engine crankcase and maintained at a
predetermined level.
• The oil is drawn by the pump and delivered through a distributing pipe into the
splash trough located under the big end of all the connecting rods.
• These troughs are provided with overflows and oil in the trough is therefore kept at
a constant level.
• A splasher or dipper is provided under each connecting rod cap which dips into the
oil in the trough at every revolution of the crankshaft and the oil is splashed all over
the interior of crankcase, into the pistons and onto the exposed portion of cylinder
walls.
• The oil dripping from the cylinder is collected in the sump where it is cooled by the
air flowing around. The cooled oil is then recirculated
Splash system

13. Pressure feed system
• Oil is drawn from the sump by an oil pump through an oil strainer and delivers
through a filter to the main oil gallery at a pressure of 200 to 400kpa.
• A pressure relief valve (fit in the pump unit or filter unit)is provided which
automatically keeps the delivery pressure constant and can be set to any value.
• When the oil pressure exceeds that for which the valve is set, the valve opens and
allow some of the oil to return to the sump thereby relieving the oil pressure in
the system.

14. • From main gallery, oil goes through drilled passages to main bearings from
where some of it falls back, some is splashed to cylinder walls and rest is
sent through the holes to the crankpins. From there it is sent to the
connecting rod web and to the gudgeon pin. After this it falls back or
effects ring lubrication
• In light duty engines, big end splash for piston and cylinder.
• Timing gears and camshaft – separate oil lines from the oil gallery through
pressure reducing valve. Valve tappets are lubricated by connecting main
oil gallery to tappet guide surfaces through drilled holes
• In case of overhead valve mechanisms – rocker arms are mounted on
hollow shafts which carry oil under pressure from oil gallery
• Oil that seeps through valve train as above is returned through drain holes,
such that the oil drains on the camshaft and timing gears to lubricate them

17. LubricationSystem–WetSump

18. Advantages
• It is less costly compared to a dry sump system
• Checking of oil level is easy

19. DrySumpsystem
• It is employed in some racing car engines and situations where the vehicle
has to be operated at a very steep angles.
• It uses an additional pump as well as a remote oil tank.
• It is used in situations when a wet sump system cannot cope with the oil
supply, in unusual or extreme conditions.
• In this system the sump can be smaller in size and can be placed
anywhere in the vehicle. Usually it is placed down so that COG is lower
• This system is more reliable but more complex and costlier due to
additional pump and high pressure oil lines.