I don't know much but simple things like,
Oil change every 5k km as Diesel engine have larger oil capacity as compared to petrol. ( 2c have 5-5.5L).
Extra bucks for oil but on other hand it requires 10w-40 or 15w-40 which is cheaper.
Plus oil + air filter.
Fuel filter change at 10-15k km. Extra bucks
Keep eye on diesel pump every now and then. I think there is some period after which it's timing is checked and corrected, which 99% mechanic can't handle. Bad pump means engine is going to die soon.
Just like Petrol engine valve clearance on diesel is I think very different due to same reason no proper mechanic or machines. Even mechanic here can't properly set valve clearance on petrol let alone diesel.
Diesel don't have spark plugs but glow plugs which I think is not easily understandable by many people. But they don't go wrong so early.
Some don't like the sound of diesel engine. Also nowadays it's expensive then petrol.
But in the end it's a personal choice.
I myself like diesel bcz of better response and drive. Way more torque then petrol engine. Rather fun to drive.