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rotax 4-stroke - oil system
912UL, 912A, 912F, 912ULS, 912S, 914UL and 914F Engines
We supply Skydrive Aerolube 10W40 for Rotax 912/914 series engines, buy here
OR
Shell Sport+4 or Motorcycle oil of a registered brand with gear additives. If using aircraft engine oil, it must be a blended oil. Must have API classification “SG” or higher. Do not use friction modifier additives. Heavy duty motorcycle oils, usually semi or fully synthetic, are most suitable. If the engine is run on AVGAS, more frequent oil change will be required. See the maintenance requirements for the engine. Refer to Rotax Service Information SI-912-016 / SI-914-019.
Motorcycle oils are recommended because they contain an additive to help lubricate gearbox components.
All information provided here is correct at the time of publishing to the best of our knowledge, but Rotax recommendations may change at any time without our knowledge. It is the engine owners responsibility to ensure that the engine is fit for flight at all times. The information is provided here free of charge and with no obligation from us to the consumer. To ensure that you have the correct and most up to date information, you should refer to the current Installation, Operators and Maintenance manuals for your engine. The information provided here may not be valid for aircraft outside the UK. Click here for ConAir SportsTerms& Conditions, including website usage policy.
EVERY 100 hours or annually for engines run on unleaded fuel.
If you find yourself using Avgas for more than 30% of the time an oil change should be performed at least every 50 hours, ideally every 25 hours. Oil change is necessary to try to flush out some of the lead contamination that ends up in the oil as a by product of the combustion process of leaded fuels.
In order to check the oil level, you MUST “gurgle” the oil, otherwise the oil level reading WILL NOT be correct. “Gurgle” as follows:
Ensure Mags are off, then turn propeller slowly, in the normal direction of rotation. The lower the oil tank is relative to the height of the crankshaft, the quicker the gurgle will occur. Pause at top dead centre to allow as much of the compression as possible to seep past the piston rings, which will help to return the oil to the tank. As the blow by gasses enter the crankcase, they push the oil out the banjo on the underside of the engine and back to the tank. When all of the oil has been evacuated, a rush of air enters the oil tank and produces the gurgling noise.
Carry out the oil level check IMMEDIATELY after the engine has been gurgled.
The oil dipstick goes into a tube in the oil tank - allow the oil to rise up the tube for a few second before removing the dipstick to check the oil level.
Oil pressure sensors may indicate incorrectly as a result of any of the following:
- Broken wires - Poor earthing
- Corroded contacts - Incorrect battery voltage
- Damaged sensors - Sender / gauge mis-match
Resistance of VDO sender is about 10 ohms at 0 bar, and around 100 ohms at 5 bar.
Rotax have introduced a solid state pressure sensor with an integral wire - more info will follow.
Rotax have changed to a Honeywell solid state oil pressure sender which does not work as a direct replacement for the old type VDO sender. To convert you will need to check if your gauge is compatible / configurable to the new sender:
ANALOGUE gauges - most analogue gauges suitable for the earlier sender will not be compatible and a new version will have to be fitted.
FLYDAT : Flydat with a round hole and a silver reset button - yes is compatible but will need a conversion kit
Flydat with a square hole and a silver reset button - yes compatible for direct replacement (in some cases a software
update may be required)
Flydat with a round hole only on thee front - not compatible
If you have another make of Electronic gauge you will need to refer to the instrument manufacturer.
It is essential to cut open the oil filter at every filter change as examination of the debris inside the filter gives a valuable information and may indicate component failure within the engine.
Tools required:
Economy Oil filter wrench - click here
or
Professional oil filter wrench - click here
Economy Oil filter cutter -click here
or
Professional Oil filter cutter - click here
Maintaining proper oil temperature is critical in today's sophisticated engines. Installation of an auxiliary oil cooler helps keep the oil temperature down. However, installation of a remote oil thermostat, in addition to an oil cooler, will help warm the oil up to operating temperatures faster. This speeds up warm up time on cold days and reduces fuel consumption. Installing a suitable oil thermostat should increase your oil temperature to a level where moisture is evaporated out of the oil and this should reduce engine internal corrosion. For details of oil thermostats that we can supply click here.
Exercise caution during installation of an oil thermostat to avoid trapping air in the oil cooler. Installation of an oil thermostat will constitute a Modification.
The matting shown on the left here is ok. The matting shown below demonstrates that there is a serious problem with the engine.
When buying oil hose for the Rotax 912/914 series engines, it is important to consider that the oil hose is under “suction” from the oil tank to the oil pump. In order to ensure that the oil hose you choose will not kink or collapse under these conditions, choose a hose that is rated for “negative pressure” or “vacuum” operation and a temperature rating of at least 150ºC. Do not bend the hose to a radius smaller than 75mm.
You must use straight or gently curved fitting to connect oil hoses. Angled fittings may cause oil restrictions. Do not use industrial fittings or banjos on the suction side - use oil fittings that do not restrict the oil flow.
1 - warm up the engine
2- return the residual oil in the crankcase to the tank - this is done by removing the filler cap and then turn propeller slowly, in the normal direction of rotation. The lower the oil tank is relative to the height of the crankshaft, the quicker the gurgle will occur. Pause at top dead centre to allow as much of the compression as possible to seep past the piston rings, which will help to return the oil to the tank. As the blow by gasses enter the crankcase, they push the oil out the banjo on the underside of the engine and back to the tank. When all of the oil has been evacuated, a rush of air enters the crankcase and produces the gurgling noise.
3 - Check (and record) the oil level.
4 - Remove plug from tank and drain the oil. Re-install and wire lock the drain plug.
5 - Refill the oil tank.
6 - Remove and replace the oil filter - don’t forget to seat the gasket and then tighten through 270º.
7 - Turn the engine by hand until the oil pressure is seen on the oil pressure gauge (remove spark plugs to make this easier).
8 - Check the security of the oil filter and mark with torque seal.
9 - Run engine and check oil filter security, oil level and check for signs of leaks.
DO NOT drain the oil cooler.
DO NOT blow out the oil hoses.
DO NOT remove the crankcase oil ports on the bottom of the engine.
No, you do not need to purge the oil system after a routing oil change. Yo do need to purge the oil system if you disconnect an oil hose or dismantle the oil tank. See Rotax SI-912-018 or the Installation Manual for instructions on purging the oil system.
Fluctuations of oil pressure within the normal operating range are not a problem, however, should fluctuations be a concern, an improved oil pressure relief valve, which reduces fluctuations, is available, click here.
On Rotax 912 / 912S engines, the oil pressure should be a minimum of 0.8 bar. Pressures up to 7 bar are perfectly acceptable - the normal range is 2.0 to 5.0 bar.
It is perfectly normal for the oil pressure to drop as the engine rpm increases - this occurs when the oil pressure relief valve opens. However if it continues to drop with rpm you may have a restriction in the oil system that should be investigated.
If the oil pressure is low, firstly check the gauge for accuracy. Secondly, it is possible to alter the relief pressure of the valve by adding a shim in the plug screw.
A word of caution - take care not to increase the pressure too far as severe damage can be done if the oil pressure is too high when the oil is cold.
Low oil pressure and high oil temperature simultaneously could be an indication of a low voltage problem or bad earth.
Click here to download a booklet from Shell Aviation called “The Answer Book”.
It is possible for a small amount of oil to get trapped in the gearbox - if the level is slightly low (but above minimum) after and engine run, do not be alarmed. Allowing the engine to stand for 10 minutes and then gurgling it should give an accurate oil indication.