http://www.e34.de/vin/index.php
Gearolje type
Fra www.statoil.no
API-klassifiseringssystemet angir giroljens kvalitet i følge GL-1, GL-4, GL-5 og GL-6. Her er det IKKE slik at stigende kvalitet angis med stigende tall. Forbokstavene GL (Gear Lubricant) benyttes for å vise at det er en girolje, og tallet forteller om mengden EP (Extreme Pressure)-tilsetning samt bruksområdet.
API GL-1 er en olje uten EP tilsetninger.
API GL-4 inneholder milde EP-tilsetninger og benyttes i en stor grad i manuelle girkasser.
API GL-5 inneholder kraftige EP-tilsetninger og benyttes normalt i hypoide gir og differensialer.
API GL-6 benyttes svært sjelden i Norge, inngår i enkelte fabrikkoppfyllinger.
Fra "Manual Gearbox Design" av Alec Stokes:
Extreme pressure additives
In some gear units, particularly hypoid gears, even the anti-friction action of a compounded oil is not sufficient to provide adequate lubrication. For this reason, lubricants with extreme pressure (EP) additives have been produced. An EP additive goes into action if the high spots on the mating teeth surfaces rub together and set up high frictional temperatures. These high temperatures react on the EP additive which through chemical activity with the adjacent metal creates a solid boundary layer of lubricant which has anti-welding properties and is formed in the exact areas of-the tooth surfaces where welding is most likely to occur. Due to the sliding action occurring between the gear teeth and the subsequent generation of heat, this layer of anti-welding lubricant is continually being ruptured and re-formed.
Extreme pressure additives are carefully made up and produced so that they react with the surrounding metal at temperatures just below the temperatures recorded at the gear tooth surfaces. Such reaction impedes the welding action that can occur between the mating tooth surfaces and therefore the additive is not consumed. It is only the sliding action between the mating tooth surfaces that depletes the additive strength.
Differing EP additives possess various degrees of activity and are produced to combat a full range of problems in a wide variety of applications. One result of the chemical action on the EP additives is that staining occurs on the surfaces of any copper-based metal. The degree of such staining is generally related to the level of EP action within the additive. ‘Full EP’ and ‘active EP’ refer to the higher grade additives used in oil, and ‘mild EP’ oils are those with lower EP effectiveness.
The more common EP agents are based on lead, sulphur, chlorine, or phosphorus, the more popular combination being lead and sulphur. Provided that the bulk oil temperature is maintained below 80°C, this combination will satisfy most of the EP requirements for gear oils, but in applications where the bulk oil temperatures exceed 80"C, this combination has a tendency to produce sludge through interreaction. Due to the more general use of higher tooth loadings and bulk oil temperatures, together with a more positive interest in health hazards within industry in the past few years, the use of lead has given way to phosphorus. The combination of sulphur and phosphorus has proved capable of dealing with these higher demands. Although they are not so effective against corrosion, this can be corrected by using corrosion inhibitors.
Konklusjon:
Det er ikke sikkert at GL-5 er bedre enn GL-4. Enkelte girkasser tar skade av GL-5 olje, spesielt de som har synkroniseringsringer av messing (kobber-basert).
