Oils for gasoline engines with GPF

ELF for dowsized engines

20 lutego 2023

Cars with downsizing engines are becoming increasingly popular on the aftermarket. However, not everyone is aware of the requirements that oils for these units must meet. ELF presents the most important ones and explains why they play such an important role.

Basically, every car enthusiast is familiar with the general principles of downsizing. The aim of downsizing is to achieve similar or even better performance from a smaller displacement than before, all while consuming less fuel and weighing less. Such goals can only be realised by over-engineering new engines, and this can take its toll on their durability.

ELF proposes to explore the aspects of downsizing engines in a little more detail. For many readers, these will be surprising. Understanding the subject is important, however, as it will probably prompt you to follow the manufacturers' recommendations on lubricants, as the correct choice of lubricants is fundamental in some respects.

Where did the GPF filters come from?

While the existence of particulate filters in diesels seems perfectly understandable, the use of analogous systems under the name GPF in petrol engines seems almost irrational. In practice, however, it turns out to have a profound justification, and the selection of suitable oils extends the life of these filters by weakening the clogging process.

Downsizing petrol engines has started to produce soot, sometimes even in considerable quantities. This is because under the enormous load of a small direct-injection engine, the fuel and air are not perfectly mixed, and zones of excess fuel are formed in the cylinders. And it is from these that soot is formed in the combustion process, which must be captured somehow. GPF systems, or gasoline particulate filter systems, are used for this purpose.

What does oil have to do with soot?

It turns out a great deal. On the one hand, its composition can reduce the formation of soot particles somewhat. On the other hand, it must have dispersion properties. The point is that soot from the combustion chamber also gets into the oil and contaminates it to some extent. Good oils have suitable dispersant properties that allow quite a large amount of soot to remain suspended and dispersed in oil. In this way, the contaminated oil is able to circulate and not clog up the channels or oil filter, and this could have bad consequences for the entire engine.

Additional protection for the timing chain

The soot in question tends to settle in various areas of the engine, including the timing chain. This is particularly damaging in the pins connecting the chain links, as it causes them to wear out. The minimum clearances on the individual pins, when multiplied by the number of pins, can „lengthen” the chain to an extent that cannot be compensated for by the tensioner. This causes disturbances in the timing phases and risks chain „jumping”. In the worst-case scenario, the lack of synchronisation of the camshafts and crankshaft can lead to hitting the valves by the pistons, and the cost of repairing this event will be enormous. Oil with strong dispersant properties prevents soot accumulation in sensitive areas and thus protects the chain from elongation.

Oil and pre-ignition

Another serious problem that internal combustion engine designers are still struggling with is the phenomenon of LSPI pre-ignition. It can be observed most often in the low-rpm range (1500-2000 rpm) when the engine is heavily loaded and heavily charged with air. Premature ignition is caused, among other things, by unburned fuel and glowing oil particles present in the combustion chamber. LSPI results in the piston skirt hitting the cylinder liner, and this leads to serious engine damage. LSPI-reducing oils are formulated to reduce the formation of these particles, which can glow within the cylinder and additionally extinguish fuel diluted in the oil film on the liners or piston rings.

The choice of the right oil in this type of engines is very important.

Specifications and approvals developed by international organisations and engine builders over the past few years have been created precisely to offset the negative effects of engine downsizing. Some of the most popular are API: SN+, SP; ACEA: C6, ILSAC: GF-6, FORD: M2C-948-B, Renault: RN17, RN 17 FE, BMW: LL 17 FE+, GM: Dexos1 Gen3, OPEL: OV0401547 - G20 and G30, etc. Unfortunately, many of these specifications exclude each other in terms of oil chemistry, viscosity, FE properties, compatibility with timing belt materials, etc. This has necessitated the release of several new products to meet the requirements of the various builders.

Products tailored to meet the needs of these new approval types have appeared in the ELF range. These include
Evolution FULL-TECH APX 0W-20;
Evolution FULL-TECH VSX 0W-20;
Evolution R-TECH ELITE FE 0W-20;
Evolution FULL-TECH FEX 5W-20;
Evolution 900 USX 5W-30.

Downsizing, which at first may have seemed a naturally environmentally friendly solution, in practice forced both engine and oil designers to work hard to achieve their goals. Without solutions to reduce soot emissions or control combustion, downsizing would be pointless. The role played by the right oils in this regard is even surprisingly important. It appears that the wrong choice of oil for modern downsizing units may not only worsen the composition of the exhaust gases (e.g. by increasing the LSPI phenomenon), but also damage the engine itself.

Andrzej Husiatyński, TotalEnergies

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TotalEnergies Marketing Poland has been operating in Poland since 1992 and has an established position in the motor oil market. It offers products from two well-known brands TotalEnergies and Elf. Since 2008, TotalEnergies also offers bitumen products and has a presence in the industrial specialty fluids market. In December 2014, TotalEnergies launched its first gas stations in Poland, thus entering the retail market. In 2021, TotalEnergies opened its first car washes and launched a project to establish an electric vehicle charging network.

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