Rotax Aircraft Engines
Rotax four stroke aircraft engines have proven themselves as reliable pieces of machinery. They can be bought as experimental (UL) or certified (A and F) engine and there are four main models (injected too) to date. The original engine is the 80 hp 912, from which the 100 hp 912S was developed and Rotax also has a 115 hp turbocharged 914 engine. In 2015 Rotax announced the 135 hp fuel injected turbocharged 915iS.
Recent engine oil has characteristics that slows the return of oil into the oil tank. The level can therefore fall below the minimum on the dipstick. For this a new dipstick is developed with a higher maximum level. Some older Rotax engines with the new dipstick will throw out the extra oil.
Bombardier Rotax Service Bulletin
SB-912-040-914-026, Oil Level Dipstick
Excerpt from the document:
It has been discovered, in some cases, that the new characteristics of some modern oils can result in a slower return of oil from the crankcase to the tank under certain conditions. This could possibly cause the oil tank level to fall to a level below the minimum. In order to help prevent this problem it is necessary to raise the minimum oil level in the tank. This is achieved by using a new dipstick with new level marks.
Introduction of a new oil dipstick for ROTAX® engine type 912 (Series) and 914 (Series). Compliance at the next oil change or within the next 100 hours of operation, but at the latest by July 1st 2003, the replacement of the oil dipstick must be conducted.
To continue reading see the pdf below: