Modern Engine Technologies and Their Impact on Motor Oils

If we take a look at the passenger car motor oil product range of any reputable oil company and compare it to the product range of the same company from 20 years ago we can barely find any overlap between the two. At the time being mineral oils were the mainstream, semi synthetics were considered premium quality and fully synthetic oils were kind of oddities. Currently, about 80% of the product range consists of 0W30 to 5W40 viscosity synthetic oils, we can also find a couple of 10W30 or 10W40 semi synthetics and maybe a 15W40 mineral oil. Some of the reasons behind this advancement is the growing requirements of the new engine and emission reduction technologies. In the following sections, we are going to introduce some of these technologies and their impact on the motor oils.

Diesel Particulate Filter (DPF)

The job of the DPF is the filtration of the micro particles from the exhaust gas of the diesel engines. This is a physical filter through which the exhaust gas flows through. To maximize the useful life of the filter it is important to ensure that exhaust byproducts do not clog it. The quality standards of the diesel fuel – in most parts of the world – already ensure the fuel’s compatibility with the filter, but as far as motor oils go not all of them are compatible. Some oil always gets burned with the fuel even in those cars which seemingly do not consume any motor oil. Therefore, it is important that the oil used is mid-SAPS or low-SAPS as required by the car manufacturer. Otherwise the DPF gets clogged in a couple 10 thousand miles and its replacement is costly. So, if you have a DPF equipped car, always use a motor oil that meets the quality requirements of the car manufacturer.

Running on Compressed Natural Gas (CNG) or Liquefied Petroleum Gas (LPG)

Even though most LPG or CNG powered passenger cars do fine with traditional motor oils, some of them may require a motor oil with maximum 1% sulfated ash content to avoid pre-ignition. In this case, it is usually correct to choose an oil that we would choose for a DPF equipped car, like an ACEA C2 or C3 quality oil. The car manufacturer’s recommendation is to be followed in this case as well.

Biodiesel

If the car manufacturer permits running on 100% biodiesel they usually recommend a shorter oil drain interval. The reason behind this is that the volatility of the biodiesel entering the oil is very low so it tends to accumulate in the oil effectively diluting it. The reduced viscosity, biodiesel contaminated oil does not provide an adequate oil film thus accelerating the wear of the engine. Furthermore, the polar biodiesel molecules replace the molecules of the anti-wear additives, but they are a lot less able to prevent wear themselves. These only apply to 100% biodiesel fuels. Regular diesel fuel with 5-7% biodiesel content does not suffer from these drawbacks.

Direct injection diesel engines (e.g. TDI, HDI, JTD, DCI, SDI, etc.)

In direct injection diesel engines, the diesel fuel is injected directly into the combustion chamber, which increases the torque and the efficiency of such engines. But this operation is also characterized by higher temperature, which results in accelerated thermal deterioration and breakdown of the motor oil. The chance of the oil being contaminated with fuel is also bigger. Many car manufacturers have their own standards for such engines, but in lack of these many European car makers recommend an ACEA A3/B4 oil for such operations. These oils provide better engine cleanliness than the regular A3/B3 quality oils.

Common rail engines

This technology is an improvement over the direct injection. Instead of the low-pressure fuel pump feeding the unit injectors there is a single high pressure (over 1000 bars) fuel rail feeding individual solenoid valves independent from the load and from the engine RPM. This can optimize engine operation thus increasing engine efficiency. This setup does not demand more from the motor oil than direct injection. An oil that is suitable for that setup is also suitable for this one.

Turbocharger

Turbocharged engines are characterized by high specific power, which means greater heat production. This heat affects the oil as well. For proper lubrication of the turbocharger’s bearings it is important to use an oil with good thermal stability and low volatility. It should also be able to keep the engine clean, which is a bigger challenge at high temperatures. Fully synthetic oils are characterized by exactly these properties so they are usually ideal fits for turbocharged engines.

Exhaust Gas Recirculation (EGR)

The goal of this technology is to reduce the emission of nitrogen oxides (NOx) but reusing part of the exhaust gas increases the production of solid particulates (for example soot) because the fuel burns worse with less oxygen present. The result is increased soot levels and accelerated oil acidification. API CI-4 onwards and ACEA E4, E6, E7 and E9 all have demands for EGR compatibility so oils meeting these specs can withstand the adverse effects of EGR operation for the duration of the oil change interval. If there is a different specification in place for a particular vehicle, the manufacturer’s recommendation should always be followed.