skip to Main Content

Airplane Light Sport Aircraft ROTAX Engine 912: Engine Oil

Wondering about Airplane Light Sport Aircraft ROTAX Engine 912 engine oil? We’ve got the answers for you here.

Oil Types

Generally use modern synthetic, semi synthetic or mineral/petroleum base (dinosaur) oil depending on fuel used
– Do not use aircraft oil because engine is modern, generally use automotive, and one step better, four stroke motorcycle oil with additives for integral gear box. Avoid motorcycle oils with friction modifiers.
– Rotax service instruction SI-912-016 provides updates
– Best is Mobil 1 MX4T motorcycle oil (also called Mobil 1 racing 4T) when using auto gas most of the time (70% or more auto-gas use)
– SHELL AeroShell Sport Plus 4 should be used if AVGAS is used 30% or more of the time
– Minimize AVGAS with Mobile 1

Oil Filters

Should use ROTAX filter because it is designed specifically with bypass pressure high enough for higher 912 oil pressures and is designed specifically for aircraft environment.
– S-LSA must use ROTAX oil filter

Oil Temperatures

– Have 120 F oil temperature before you go to takeoff power to make sure oil goes through filter rather than bypassing filter (with ROTAX filter)
– After market filter may bypass oil filter at much higher temperatures and is not recommended
– Ideally, oil temperature should reach 190 degrees sometime during flight to assure oil temperature in tank is at least 212 f (100C) to boil out moisture from oil.
– Oil temperature is measured at coolest point in engine after oil tank/reservoir and oil cooler
– preferred operating oil temperature reading at is from 190 to 230 F
– Maximum operating oil temperature reading is 266 F
Oil Weight
– Higher oil weight/thicker oil is preferred for hotter climates (such as 15/50W), however 10/40W can also be used. 10/40 weight universally used for normal/colder climates. See ROTAX Operators manual for specific oil weights for outside temperature ranges.

Oil Pressure

IMPORTANT – watch gauge especially during startup for pressure within 5 seconds
– running with no oil pressure will destroy engine.
– Monitor engine oil pressure for engine startup, especially for initial startup or after changing oil. If you do not see acceptable oil pressure reading (typically 29 to 73 PSI) within 5 seconds, shut down engine immediately. Do not assume gauge is bad. Use additional/separate mechanical oil pressure gauge if necessary to resolve “no oil pressure” problem on engine.

Rotating Propeller for Checking or Changing Oil

Rotating the propeller pumps residual oil from the engine into the oil tank so the oil tank is completely full. This would be required for two situations:
o You are getting ready to change the oil and you want to make sure all the oil is in the tank before you drain it, or
o You checked the oil and it reads low on the dipstick. Before adding oil, you rotate the propeller to get the oil up to the calibrated level for an accurate oil level check. Do not add oil before rotating propeller or you could over fill tank.
– Facing propeller, always turn prop to top left/counterclockwise. Never turn propeller clockwise or you draw air into the engine valve train which is bad for the engine.
– Important process before accurate oil check or oil change is to ”burp oil system”
  o Take oil cap off and put where you will never forget to put it back on
  o Pressurize with propeller/engine compression stroke and listen for gurgle out of oil tank (burp). Some installations can take 20 rotations of the propeller to achieve the burp. Be patient.
– Having burped tank, oil is returned to tank for accurate measurement and changing.
– Use/update to square handle dip stick
– When checking oil, oil level should fall within the flat portion of the dipstick.
– Assure cap is properly secured to avoid oil loss during flight

Oil Change Tips and Important Tank Issues

• Use “hold back wrench” on oil tank for fittings disconnection/connection.
• When removing the oil lines from tank hold them up to
   o not drain oil out and make a mess
   o not let air get into oil lines
• oil tank air vent at top near cap
• tank markings – oil OUT of oil tank, fitting oil IN to oil tank
• oil tank has additional fitting on top of tank near cap used for 914 turbo oil input port
• Disassembly of tank, over center ring off, remove top, screen, and bottom plate
• Oil tank OUT pickup, note tube from bottom of tank
• Oil tank IN fitting at angle around outside of tank keeps sediment and large air bubbles returned from engine outside of screen.
• Separator plate at bottom of tank is to isolate sediment at bottom outside of screen from pickup tube
• Screen also separates and breaks up air bubbles returning from engine
• Clean out bottom of oil tank when disassembling tank for oil change
• To assemble oil tank – base plate feet on bottom, screen fits on outside of separator plate with feet down, “O” ring in good condition on, cover on, and clamp ring on. Make sure and properly catch lips of the can and cover with the over center clamp. Dip stick and cap on.
• Note oil tank markings: IN is oil into tank from bottom of engine. Connect the engine supply to the fitting marked OUT on the oil tank (this line goes to the oil cooler and than from the engine oil cooler to the engine pump). Connecting these lines incorrectly will not supply oil to the engine and likely lead to serious engine damage.

Oil Filter Inspection

• Cut case with special tool like tubing cutter, remove the filtering element by cutting along sides, spread filter element out to inspect for minerals or metal. Bypass valve can be seen easily with oil filter cut open.

Back To Top