To check the oil on the Yamaha you have to have a warm engine so I normally do it when I stop for petrol. This morning I left Montevideo and after about 20km I decided to pull over to check it. When I got off the bike most of the oil was in a puddle on the ground under the sump. I hoped it might just've been that the sump plug had come loose but unfortunately it wasn't that simple. I started the engine and saw that the oil was dripping from somewhere higher up. Fortunately I'd bought a litre of spare oil in Buenos Aires (I don't normally carry that much) so I put that in and decided to limp back into Montevideo. I came to a petrol station after 16km so I put in another litre of oil and got directions to a bike shop about a mile away. Within about 20 minutes the culprit had been identified - a leaky seal behind the front sprocket. They managed to track down a replacement and within a couple of hours I was on my way again. If I hadn't have stopped to check my oil I probably wouldn't have known anything was wrong until the engine seized.
I'm glad to report the workshop, like all the others I've found myself in on this trip, conformed to the international blueprint for garages - one guy doing a bit of work and 3 or 4 others who stand around drinking tea.