Motul MOTYLGEAR 80W-140

Worth knowing

The value of 40 mm²/s at 100 °C does not fit the band that the February 2019 edition of SAE J306 sets for grade 140: 24.0 to 32.5 mm²/s. By that table it falls into grade 190, 32.5 to 41.0 mm²/s. The data sheet claims grade 140 is kept after the 20-hour KRL test under the July 1998 edition, when this grade still covered 24 to under 41 mm²/s. So the “140” here and, for example, in Motul GEAR COMPETITION 75W-140 with its 24.7 mm²/s stand for very different thicknesses. A table of these limits is in the article on GL-4, GL-5 and gear oil viscosity.

By codes, MOTYLGEAR 75W-90 does not differ from it: both state API GL-4, GL-5 and MIL-L-2105D. The difference is in the figures: 18.1 against 40 mm²/s at 100 °C, 114.1 against 289.7 mm²/s at 40 °C, pour point -51 °C against -27 °C. Replacing a prescribed xxW-90 oil with 80W-140 under very heavy loads, shocks or high temperature is recommended by the Motul data sheet, so by the oil maker, not the gearbox maker; this list has no carmaker codes.