Yanmar AF-15 to AF-18 engine oil and fluids: which ones and how much?
The right engine oil and fluids for the Yanmar AF-15, AF-16, AF-17 and AF-18 are cheap insurance against costly repairs. In this article you'll find all the fill quantities from the original manual, which modern oil to use today, and how to change the engine oil, transmission oil, front axle oil and coolant step by step.
Suitable for the entire series: Yanmar Forte AF-15, AF-16, AF-17 and AF-18. The quantities apply to all versions; only the turf version differs slightly (engine oil 2.3 l, transmission 19.5 l, cooling system 3.0 l).
Yanmar AF-15 to AF-18 fill quantities
| Component | Quantity | Type |
|---|---|---|
| Engine oil | 2.4 litres (turf: 2.3 l) | Diesel engine oil, e.g. 15W40 |
| Transmission / hydraulic oil | 20 litres (turf: 19.5 l) | UTTO/STOU transmission oil GL-4 (original: Yanmar TF500) |
| Front axle oil (4WD) | 2.0 litres | Same transmission oil (TF500 type) |
| Coolant | 3.6 l radiator + 0.4 l expansion tank | Water + ethylene glycol antifreeze (LLC) |
| Fuel | 20 litres | Diesel oil; below −10 °C winter diesel |
| Lubrication points | — | Multipurpose grease no. 2 |
Yanmar AF series engine oil: which one should you use today?
The manual from the 1990s specifies a diesel engine oil of API class CC (back then "Yanmar Super Oil"). That class no longer exists on the shelves; a modern 15W40 diesel oil amply meets and exceeds that requirement and is the standard choice for these engines in our climate. Change the engine oil every 100 hours (the first time already after 50 hours) and replace the oil filter every 300 hours. Always check the level before starting or with a cold engine, with the tractor on level ground. The sump holds 2.4 litres: with a 5-litre jerrycan you can do two oil changes.
Changing the oil is simple: remove the drain plug at the bottom of the sump while the engine is lukewarm, let it drain, put the plug back and fill via the filler cap up to the top mark on the dipstick. Then start the engine briefly, wait until the oil pressure light goes out and check the level again.
Yanmar AF series transmission oil: one oil for gearbox, hydraulics and power steering
Important to know: on this series, the transmission oil doesn't just lubricate the gearbox, it's also the hydraulic oil for the lift and power steering. So never use a regular gearbox oil (GL-5), but a UTTO or STOU transmission oil suitable for wet brakes and hydraulics — the modern equivalent of the original Yanmar TF500. The gearbox holds as much as 20 litres and has four drain plugs: at the bottom of the transmission housing, under the 4WD drive housing, and left and right under the rear axle housings. Drain when the transmission is warm, replace the line filter at the same time (every 300 hours), and top up via the opening on top of the hydraulic housing. Check the level with the dipstick between the footboards.
The front axle (4WD) has its own oil supply of 2.0 litres with three drain plugs (centre and left/right at the bottom) and three filler openings. Use the same transmission oil and change it every 300 hours. Note: do not screw in the dipstick at the top right of the front axle when checking the level.
Yanmar AF series coolant and antifreeze
The cooling system holds 4 litres (3.6 l radiator + 0.4 l expansion tank). Change the coolant every year — antifreeze loses its anti-corrosion properties after a year. From the factory, the fluid is mixed to −25 °C (approx. 45% antifreeze). The mixing table from the manual:
| Protection down to | −5 °C | −10 °C | −15 °C | −20 °C | −25 °C | −30 °C |
|---|---|---|---|---|---|---|
| Antifreeze proportion | 18% | 27% | 34% | 39% | 45% | 51% |
When changing the coolant, flush the radiator with clean water until no more dirt or rust comes out, and let the engine idle for 5 minutes after filling to mix the fluid. If the level in the expansion tank drops slightly on its own, top up only with clean water.
Yanmar AF series fuel and bleeding
Fill with regular diesel oil; use winter diesel at temperatures below −10 °C. After the tank has run dry or the fuel filter has been replaced, the system needs to be bled — and with this series that's surprisingly easy: fill the tank, set the fuel tap to "O" (open), check that the filter housing fills up, set the throttle lever to maximum and run the starter motor. The system then bleeds itself. Preferably never let the tank run completely empty; at 20 litres the reservoir isn't large, so refuelling before a long working day prevents hassle.
