Two-stroke oil

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Under two-stroke oil is generally understood as a special type of engine oil that is designed so that it is burned in the combustion chamber and consumed. Together with gasoline, it forms the two-stroke mixture .

The two-stroke oil can be fed to the Otto two-stroke engine via separate lubrication , or it is premixed with the petrol in the tank in a certain ratio specified by the vehicle manufacturer.

Modern two-stroke oils are designed to be self-mixing and are simply poured into the tank when refueling according to the manufacturer's instructions.

Some two-stroke engines require different oils, for example the two-stroke diesel engine . The flushing, lubrication and flow conditions in the supposedly simple two-stroke engine are anyway so complex that it is always worthwhile to study the engine manufacturer's instructions carefully. Especially with regard to the specified mixing ratio for mixed lubrication.

variants

Like all engine oils, two-stroke oil is now available in three different variants:

  • Two-stroke oil from petroleum: made from base oils that are obtained directly from petroleum distillates .
  • Semi-synthetic two-stroke oil: made from a mixture of mineral oils and synthetic base oils.
  • Fully synthetic two-stroke oil: made from base oils that are obtained synthetically or not directly from petroleum distillates.

In principle, an engine oil for two-stroke gasoline engines does not differ from an engine oil for four-stroke gasoline engines. The base product only becomes an engine oil that is especially suitable for two-stroke engines when the appropriate additives are added.

Until the 1960s, many drivers of two- stroke vehicles used unalloyed single-grade oil (mostly SAE 30) instead of special two-stroke oils. This was then mixed with the gasoline in mixing cans that were available at every petrol station (or that were carried in the trunk) using a hand pump and a lot of power. Some vehicle models, such as the DKW Munga , even had a mixer built into the tank, with which the mixture could be mixed when refueling and - after longer periods of inactivity - before starting the journey.

Today, however, you can trust that the self-mixing two-stroke oils with additives will better meet the special requirements of the two-stroke gasoline engine. There are even specially adapted, self-mixing two-stroke oils for two-stroke oldtimers with their basically different sealing materials.

tasks

Essentially, a good two-stroke oil should do the following:

  • Protect cylinder liners and moving engine parts such as pistons , piston rings and roller bearings from wear by lubrication (or reduce the latter to a minimum).
  • Protect the piston from the dreaded jamming or seizure in the cylinder by lubrication. For motorcyclists and pilots of light aircraft in particular, piston jams and piston seizures are an immediate danger to life.
  • Prevent piston ring sticking , piston varnish and clogging of the outlet slots through clean, residue-free burn-off.
  • Prevent bridging between the electrodes of a spark plug just as reliably as self-ignition and glow ignition of the hot engine.
  • protect the rolling bearings from corrosion.
  • mix well and evenly with the gasoline.
  • Do not attack the seals, so that the elastomers do not become brittle, shrink or soften.
  • Leave as little smoke and odor nuisance as possible when burned.
  • Leave as few impurities as possible in the exhaust and exhaust system (oil carbon)

In the case of two-stroke oil, which is to be used in boating, there is also the fast biodegradability required in many countries.

If the two-stroke oil is to be used in racing, there is still a particular problem arising from the heat generated. The oil has to lubricate reliably even at temperatures of 150 ° C and more. Special racing oils therefore achieve flash points of 240 ° C. Commercial two-stroke oils cannot do this. Only highly viscous oils specially developed for this purpose are designed for such temperatures. However, this design is often at the expense of low smoke, odor pollution and engine cleanliness.

Norms

American Petroleum Institute together with Co-ordinating European Council for the Development of Performance Tests for Lubricants and Engine Fuels:

  • API TC / CEC TSC-3 is the name of the valid standard after the test procedures for API TA / CEC TSC-1 and API TB / CEC TSC-2 can no longer be carried out due to a lack of test motors.
  • API TD / CEC TSC-4 is a special test standard for two-stroke oils in outboard motors.

Japanese Automotive Standard Organization together with International Organization for Standardization:

  • JASO FA
  • JASO FB ~ ISO EGB
  • JASO FC ~ ISO EGC
  • JASO FD
  • ISO L-EGD makes the highest demands in these test cycles, while JASO FA only ensures a very simple lubricant quality.

National Marine Manufacturers Association: The current standard is NMMA TC-W3, which places particular emphasis on the requirements of water sports.

Thailand Industrial Standards Institute: especially for the Thai market, two-stroke oils must be tested according to TISI 1040. Because of the high density of two-stroke vehicles in Thailand, the main focus of this test standard is on the low-smoke content of the two-stroke oil.

See also

literature

  • Jürgen Stoffregen: Motorcycle technology. Basics and concepts of engine - drive and chassis, 8th edition, Springer Fachmedien, Wiesbaden 2012, ISBN 978-3-8348-1716-7 , pp. 269-273.
  • Fritz Ullman, Wilhelm Foerst (ed.): Encyclopedia of technical chemistry. Volume 15, Urban Verlag, 1964, pp. 243-244.