Out of curiosity I googled the flow rate of the 912 oil pump, 16 litres per minute at 5500rpm. Seems like a lot.
I then asked Ai this hydraulic question about suction hose size.
I can see why rotax wants the oil hot before high rpm operation.
Overview
For a hydraulic suction line operating at a 16 LPM flow rate and a length of 0.8 meters, you require a hose with a minimum Inner Diameter (ID) of 3/4 inch (19.05 mm), also known as a Dash -12 size.
Sizing Analysis & Criteria
In hydraulic systems, keeping fluid velocity low in the suction line is critical to prevent pump cavitation. Industry engineering standards recommend a suction line fluid velocity between 0.6 m/s and 1.2 m/s. [1]
The fluid velocities for standard hose sizes at 16 LPM are calculated as follows:
Hose Size (Dash)
Inner Diameter
Fluid Velocity
Recommendation
Dash -8
1/2" (12.7 mm)
2.11 m/s
Too Small (Causes high friction & risk of cavitation)
Dash -10
5/8" (15.9 mm)
1.34 m/s
Borderline (Slightly exceeds recommended velocity)
Dash -12
3/4" (19.05 mm)
0.94 m/s
Ideal Fit (Perfectly within the 0.6–1.2 m/s target)
Dash -16
1" (25.4 mm)
0.53 m/s
Oversized (Safe, but unnecessary for a short 0.8m run)