What does 15W40 tell us?
Lubricaiton has a viscosity of 15 in the WINTER
Thicker viscosity of 40 when engine warms up
Want thinner oil when cold starting
What is the purpose of engine lubrication?
Prevent friciton and wear
Help cool parts
Clean and hold dirt
What happens furing boundary lubrication?
Oil keeps surfaces form seizing but SOME contact occurs
Usually occurs under heavy load and at low speed
When is oil (lubrication) at its higher and lower viscosity?
When engine is cold = higher viscosity
When engine is at normal operating temp = lower viscosity
What do oil pressure sensors measure?
Oil pump pressure
NOT pressure due to hydrodynamic forces
What is a positive displacement pump?*
Positive displacement (PD) pumping moves fluid by trapping a fixed volume in a chamber and mechanically forcing it out, creating a constant, steady flow regardless of pressure changes, making them great for high-viscosity liquids or precise dosing, unlike centrifugal pumps that use velocity.
All oil pumps are positive displacement pumps
What happens if oil temp is too high or too low?
Too cold = oil becomes too thick to flow and lubricate engine parts
Too hot = oil becomes too thin to provide sufficient film strength
What is the max temp oil should be?
150C
What are the two ways the oil pump can be operated? And how fast do they turn?
Distributor-driven oil pump = turns pump at 1/2 engine speed
Crankshaft-driven oil pump = turns at same speed as crankshaft
What are the two types of oil pump?
ROTOR-type fixed rate pump
GEAR-type fixed rate pump
Name the components of the lubrication system
Oil pump
Oil sump
Oil cooler
Oil filter (cannister or paper type)
Oil galleries
What allows the pressure to be regulated in the lubrication system?
Pressure relief valve
What type of timing belts are there?
Dry timin gbelt
Wet timing belt = lubricated chain
What happens if the oil filter becomes blocked?
Oil can still flow through the BYPASS
How does the oil pressure switch (oil light) become activated when oil levels are low?
The switch has a bolt with a hole thorugh teh middle and a diaphragm
When the engine is on and pressure is built up = diaphragm is pushed upa nd two contacts touch
When the engine is off or pressure is too low = small spring can push diaphragm back down so no contacts touching
What may cause low oil pressure?
Worn bearings
Oil pump failure
What does SAE stand for?
Society of Automotive Engineers
Why do you want lower viscosity when engine is running cold?*
To ensure rapid circulation and lubrication of all engine parts during startup
Thinner oil = less drag
How are oil filters fitted to engines? And what is used as a filter?
‘Spin-on’ iftting with an O-ring seal to prevent leakage
Paper element traps small metal, rust, carbon, or dirt particles
What is the purpose of a head shield?
Used to keep engine heat away from cooled oil
Are oil coolers common?
Normally only used for heavy-duty applications, such as turbocharged engines or trailer towing vehicles
How does dry sump lubrication work?
Uses multiple pumps and an external oil reservoir for superior oil management
Oil is continuously scavenged from a shallow sump and stored in a separate tank, then pumped back under controlled pressure to critical engine components
Where are dry sumps used?
High-performance RACING cars requiring consistent oil supply
Aerobatic AIRCRAFT operating in INVERTED position
Large DIESEL engines demanding robust lubrication
Extreme OFF-ROAD vehicles facing severe angles
What is the purpose of the scavenge pumps?
Continuous Oil Evacuation
Scavenge pumps relentlessly remove oil from the engine sump = preventing pooling that could cause starvation or drag during dynamic manoeuvres
