Paul emailed me last night and asked the following question:

Hi John,

Sorry to bother you i put engine oil in my two stroke tank on my aprilia I didn’t start the bike and drained tank straight away and filled back up with 2 stroke. Will this cause any problems?

Thanks

Paul

The engine draws oil from the tank using a small pump located at the top of the engine on one side. Since you’ve not started the bike up, no oil should have been drawn through it and you did well to drain it straight away.

The oil pump is designed to pump only two-stroke oil, which is of a different viscosity to gearbox oil. If you had started the engine up, the heaver gearbox oil could have overloaded the pump and caused no oil to reach the cylinder.

Engine oil is used to lubricate the gearbox internals, reduce corrosion, improve sealing and cool the engine. As there is no pump to move the oil around, and only the lowest parts of the gearbox being bathed in oil, a higher viscosity oil is required to ensure lubrication throughout the gear train.