Advantages of petrol engines for model aircraft:
- Petrol has a greater energy density than methanol so you only have to burn about 1/2 as much for the same power output, If it is a fours stroke petrol engine it is even noticeably more efficent again..The net effect of this is that you have to carry less fuel on board.
- Petrol is cheaper than methanol/nitro/oil mix, so running costs are down.
- The oil ratio is much much less that with methanol, petrol / oil ratios can be 40: 1 of higher, so much less mess on your air frame. I run 20:1 because a lot of my engines are foustrokes and they need higher oil content for some very good reasions. Two two stroke also dont mind 20:1 so thats what they get also. Never fouled a plug and very little oil mess after many flights, easly cleaned with Prepsol ( Prepsol is a wide boiling range, low aromatics, and hydrocarbon solvent Prepsol has high solvency for greases, oils and silicones making it ideal for cleaning surfaces prior to painting.)
- Electronic ignition means more reliable running.
- More elaborate carburetors that compensate for barometric pressure, less tuning required.
- No rust problems with bearings like you get with methanol
Disadvantages
- More volatile fuel, higher fire risk.
- Usually larger engines, but both OS and Saito make small petrol engines that are fantastic.