For those of you regular readers out there in radio-land, matatus are mini-buses that roam the streets of Nairobi. Usually their drivers are among the most rude and selfish humans you can encounter on this planet. It is customary to stay in the middle of the lane when your passengers are loading and unloading. (Thus, traffic gets further snarled and drivers, such as myself, get further frustrated.)
But one thing is sure - they need good oil. Their engines face extreme stress dealing with stop-and-go traffic, dusty conditions, and probably long intervals between maintenance.