There’s no doubt you will have noticed that Hybrid vehicles are becoming increasingly prominent on Australian roads and in workshops nationally. In fact, a record number of hybrid cars were sold in Australia in 2020 – almost twice as many as the year prior.
Official 2020 new-car sales figures released Jan ‘21 by the Federal Chamber of Automotive Industries (FCAI) show 60,417 Hybrid vehicles were reported as sold last year, an increase of 93.7 per cent on the 2019 tally of 31,191.
While the term hybrid is typically used as a “catch-all”, the reality is that hybrids come in a variety of forms. These include:
Mild Hybrids have a small electrical system made up of a motor and a battery pack, which is charged by the internal combustion engine during normal driving.
The motor provides a boost to the powertrain, but it is not capable of moving the vehicle significantly on its own.
Full Hybrids have more powerful electric motors. These are capable of moving the vehicle up to a certain speed or until the battery is discharged.
The battery that supplies energy to the motor is larger than that of a mild Hybrid. It provides a significant electric-only range, making it ideal for urban driving. The battery is recharged by the engine when it operates, and in some systems can also be recharged by energy recovery systems such as regenerative braking.
Plug-in Hybrids are similar to full Hybrids, with a powerful electric motor or multiple motors, but also have a large battery that can be charged without using the engine.
The motors are capable of moving the vehicle on their own up to a certain speed or until the batteries are discharged. The batteries that supply energy to the motor provide a significant electric-only range, making a plug-in Hybrid ideal for urban driving. Re-charging the battery by plugging into domestic or commercial electricity supplies delivers additional range without consuming fuel, further improving fuel economy.
RANGE-EXTENDED ELECTRIC VEHICLE
Range-extended electric vehicles have a large electrical system, where the motor or motors are the only means of moving the vehicle. Primary battery charging is provided by plugging into domestic or commercial electricity supplies.
Extended vehicle range is provided by the addition of a small internal combustion engine. The engine alone has no ability to drive the wheels. Instead, it powers a generator to maintain the charge level of the battery. Regardless of form, the demanding conditions of modern urban driving stress a Hybrid engine and drivetrain in different ways compared to a conventional car. This has material implications for engine and transmission oils.
WHY HYBRID VEHICLES ARE DIFFERENT TO CONVENTIONAL VEHICLES
At the lower vehicle speeds of urban driving, a Hybrid drivetrain will use the motor for e-drive with the engine off. This e-drive capability leads to a doubling of input speeds through the Hybrid vehicle transmission.
When the vehicle speed increases or the total range exceeds the drive available from the battery, the engine is switched on and engaged to drive the vehicle. As a result, the Hybrid vehicle’s engine will be off or operating at low demand in this urban style of driving.
When the driver then wants to travel further at higher speeds (for example on-highway driving) the engine will be switched on and ramp-up to meet the high demand very quickly. The Hybrid transmission is also exposed to higher torque in these rapid start-up conditions.
In this condition, the engine temperature will increase to that of a conventionally powered vehicle. Due to lower temperatures and longer periods with the engine off, Hybrid engines also experience higher rates of fuel and water dilution in the oil, relative to a conventionally powered vehicle.
All of these differences can have an effect on the lubrication requirements of the car – the oil must be able to cope with the increased stresses of higher speeds and faster ramp-up times and prevent wear from many more stop-starts, all across a wide range of operating temperatures.
THE ULTIMATE TEST FOR A HYBRID VEHICLE
This experiment was run under controlled conditions to replicate severe Hybrid vehicle operation, such as frequent stop-starts and low vehicle speeds, as well as high-speed cruising and high power outputs that might be experienced during journeys in a Hybrid.
THE 24-HOUR NYCC ENGINE TEST
The New York City Cycle (NYCC) is a test used by the Environmental Protection Agency (EPA) in the USA to evaluate vehicle emissions. The cycle tests vehicles on a rolling road over a low-speed urban style of driving, with frequent stops to simulate real-world traffic conditions in one of the busiest cities in the world.
As the internal combustion engine (ICE) in a full Hybrid or plug-in Hybrid switches on and off throughout the journey when required, the total number of stop-start events in its lifetime can be over 500,000* – ten times more than a conventional car.
The NYCC, with frequent stops, has been extended to make the test more severe by including maximum power and highspeed cruising. The test cycle was repeated 120 times over a 24hr period. In each cycle the engine stops and starts more than ten times, making over 1,200 stop-start during the test – an extreme test designed for a Hybrid vehicle.
SAY “HY” TO CASTROL’S RANGE OF TESTED IN HYBRID PRODUCTS
Hybrid lubricants need to be efficient over a much wider temperature range than in a traditionally powered car.
Internal combustion engines are very flexible and can operate at a wide range of speeds but are most efficient at relatively high RPM.
Hybrid vehicle engines are designed to operate at these efficient speeds, however this can mean they suffer from the loss of torque found at lower engine speeds.
A Hybrid’s electric system makes up for this, with the motor providing torque at lower speeds.
Operating in this way means Hybrid engines rapidly speed up to high RPM. This speed ramp-up can be around 10 times faster than in a conventionally powered car1.
Efficiency gains can also be made when the engine is operated at higher engine loads. Compared to traditional engines, Hybrid engines spend longer at higher percentages of their maximum output.
This means the engine can work up to four times harder than in a conventional car2, putting critical parts and oil under increased stress.
Tested in Hybrid3 at maximum power, Castrol EDGE with Fluid TITANIUM rapidly transforms to be stronger under pressure and reduces friction – giving Hybrid drivers the confidence to unlock the very edge of performance. Castrol EDGE – unlock the true performance of your engine.
CASTROL MAGNATEC STOP-START
The engine in a Hybrid system only operates when required. In typical urban driving, this is often for short periods of time before shutting down again. Incredibly, across a Hybrid vehicle’s lifetime, the number of stop-start events can be over 500,0004. That’s 10 times more than a conventional car.
Because of this, the oil’s operating temperature in a Hybrid can be up to 40ºC cooler than oil in a conventional vehicle5. However, in certain operating conditions, the oil temperature can reach that of a conventional car. This means the oil has to be effective over a wider range of temperatures.
Tested in Hybrid6, Castrol MAGNATEC STOP-START with Intelligent Molecules contains special molecules that form a self-healing layer that constantly protects against stop-start wear, providing up to 20 per cent better stop-start wear protection**. It dramatically reduces both warm-up7 and stop-start8 wear by up to 50 per cent.
Castrol MAGNATEC STOP-START – instant protection from the moment you start. Every time you start.
Combining engines with electric systems and delivering power smoothly to the wheels places immense stress on the drivetrain. Increased torque and intelligent drivetrain systems can double speeds inside the transmission9. Transmission fluids can be exposed to increased shear stresses, leading to the potential for a loss in viscosity – as well as foaming – increasing the risk of damaging metal-to-metal contact.
Furthermore, electrical systems including the motor are often integrated with the transmission and submerged in the transmission fluid. This can present material and electrical compatibility issues, and increase the potential for short circuit and electrical failure.
In the Transmission Fluid Test, Castrol TRANSMAX with Smooth Drive Technology™^^ was tested under controlled conditions in a Toyota Prius CVT Hybrid on a rolling road to simulate these demanding stop-start conditions for 100,000km.
During the test, the vehicle was evaluated for driveability on the road and at the end of the test, the transmission was completely stripped and assessed for parts damage and the used oil analysed. No sign of any damage was observed and the used oil showed extremely low wear particles. Active control molecules help to maintain original viscosity under severe shear stress and fights against lubricant foaming, protecting vital transmission parts.
In demanding Hybrid transmissions, Castrol TRANSMAX with Smooth Drive TechnologyTM provides effective viscosity control. Castrol TRANSMAX with Smooth Drive Technology™ – enabling longer transmission life.
ACCELERATING THE EVOLUTION
Castrol is committed to helping to advance the auto-industry’s path to an electricity-powered recovery.
Read more at their global research study, ‘Accelerating the EVolution’ – castrol.com/EV.