I suddenly mixed the engine oil into a diesel tank that are use for diesel generator set for?

Engine oil is just fine in a diesel. I used to drive Mercedes Benz diesels in limo service. When the mechanic changed the oil he would always put the old oil in the fuel tank, only checking that the tank was at least three quarters full of fuel. Sometimes it would clog the filter, but we just put more fuel in the tank and it cleared right up.