Forward dating mot
Forward dating mot
If you wish to think about this in a different way, imagine the oil is rated at 80W20000, & THINK about what that means.Thus, at most any temperature you will be riding at, even after a full warm-up, the oil is thicker, a lot thicker.
For example, using 80W145: The oil at any normal operating temperature will ALWAYS be thicker than if the oil was any lighter grade, including 80W90. #2: This shows how a typical transmission, in this case a drum type cam similar to a Classic K bike, might shift. #4: Some information how a transmission works; /2 transmissions, testing, details. Link #1: From the BMW Factory School on the 5 speed gearbox and both early and late clutches.I have no objection to it being used in the driveshaft (of those models using oil there).In fairness, I will also note here that one experienced transmission rebuilder, Tom Cutter, my words here, believes synthetic gear oil in your Airhead is not good, leading to unspecified WEAR.There is no question in my mind, that HIGH QUALITY SYNTHETIC GL5-rated oils will, or can, PROLONG the life of your transmission (& rear drive).
That does not mean that they should always be used.
BMW did not restrict use of petroleum and synthetic oils, stating only to use a GL5 oil, & that it be a Brand Name (BMW-speak for "quality ").
While straight grades are listed in the Owner's Handbook, the only listed multigrade oil is 80W90.
I recommended that you do use them unless: you live in an area where the temperature that you start the bike at will be ~100F or more (that also means the un-started engine temperature generally), and that you will be riding fast &/or with heavy loading, or pulling a sidecar or trailer ...in very hot weather ... There is an exception; some transmissions will stiffen-up gear changing when the oil is hot.
There are oils available that replace the "90" with 120 or even 145.
While there can be other causes that a change to a thicker oil will not help, in this instance you CAN try the thicker oil, such as 85W140 or similar.