Two-stroke mixture

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Two-stroke mixture is a colloquial term for the semantically correct term two-stroke mixture, a fuel for two-stroke gasoline engines. This in turn is a mixture of fuel and lubricant ( two-stroke oil ) for crankcase-flushed two-stroke engines with external mixture formation . Two-stroke engines with internal mixture formation ( two-stroke diesel , gasoline engines with direct injection ) consequently cannot be lubricated with a two-stroke mixture , as the combustion air only flows through the crankcase and the fuel is only added to the combustion chamber after it has flowed over. Other methods such as fresh oil lubrication or circulating lubrication, possibly cylinder lubrication, are required here.

Mode of action

In the case of the two-stroke gasoline engine with crankcase flushing, the moving engine parts are lubricated with the mixture lubrication by lubricating oil added to the fuel (possible mixing ratios: 1:15 to 1: 100, depending on the instructions of the engine manufacturer), as is still the case today with many scooters , mopeds , outboard engines , small engines ( Chainsaws , lawn mowers , model making engines), less common with motorcycles . In the case of cars, this was partially the case until the end of the 1980s, the best-known are probably the GDR two-stroke engines such as the Trabant 601 , Wartburg 353 or Barkas B 1000 .

An alternative to mixed lubrication is fresh oil or separate lubrication . Here, the separately carried oil is targeted by a pump either into the intake of the engine or directly to the parts to be lubricated, such as. B. crankshaft bearings promoted.

Both methods have in common that it is a loss of lubrication and the lubricant is lost after passing through the engine.

Availability and manufacture

Gas stations

Dispenser for two-stroke mixture

In the GDR, due to the large number of mixture-lubricated two-stroke vehicles, premixed two-stroke mixes 1:33 and 1:50 were offered across the board (“ carburetor fuel ”, see Article Minol ). With the extinction of the two-stroke engine, the range was increasingly thinned out.

Another option - also in West Germany - was to refuel at a two-stroke pump , moped pump or a moped refueling device . These devices, designed for smaller delivery quantities, were mostly set up mobile on the petrol station premises and consisted of a cylindrical fuel tank made of sheet steel in the lower part and a mixing device mounted above it, in which the mixture was "fresh" prepared during the refueling process. For this purpose, gasoline (still without oil admixture) was pumped up from the container below - usually in half-liter increments - into a glass cylinder provided with calibration marks and provided with oil from a second, smaller container in the previously selected mixing ratio with a hand pump or pneumatic . After the mixing procedure, the mixture was allowed to run freely from the mixing glass into the vehicle tank using a simple dispensing hose. With self-service had before refueling tokens - often also for every one pint - be purchased at the box office and are then deposited into the machine, causing the pump-up or mixing. Since mopeds, scooters and light motorcycles are increasingly equipped with separate lubrication or even with four-stroke engines, such devices are now (as of 2018) only very rarely seen.

Equipment gasoline

A pre-mixed, ready-to-use two-stroke mixture based on alkylate petrol is available especially for use in agriculture , forestry and horticulture . This is designed for use in chainsaws and other motor-driven handheld devices and is usually offered in a 1:50 mixture ratio. Due to its composition, it causes fewer harmful emissions than normal petrol station gasoline with two-stroke oil, which is relevant for those people who are directly exposed to the emissions of such machines. These fuels are offered in the agricultural and forestry supplies trade - also under the name special fuel - in various container sizes.

Mix it yourself

Two-stroke mix can also be mixed by yourself. To do this, the amount of oil required for the amount of fuel must be calculated depending on the desired mixing ratio or taken from a mixing table. The oil is added to the fuel in a suitable container (for example a canister approved for fuel ) and the container is shaken briefly. In the case of longer storage, it must be taken into account that the oil can separate again and sink to the bottom.

Individual evidence

  1. Druzhba-4 petrol chainsaw and its modifications. Technical description and instructions for use. Soviet Union, around 1985, no further details.
  2. Example of a “moped refueling device” , accessed on May 27, 2016
  3. Special fuel instead of regular gasoline - information from UK Saxony , accessed on May 27, 2016
  4. Example of a mixed table , accessed on May 25, 2019.