I believe they are different densities and the unleaded will sit on top of
the diesel like salad dressing. I might be better to drain off the tank
before the diesel runs out and you start to get unleaded into your engine.
As the level of diesel gets lower the sloshing about will cause some of it
to be drawn into the engine and it will start chugging.



I might well be wrong but the unleaded doesn't burn until the compressed and
hot diesel ignites thus causing a kick when the unleaded ignites. Another
possibly wrong fact is that putting diesel in an unleaded car is worse as
the diesel sinks to the bottom guts sucked into the engine and fails to
ignite thus filling up the cylinders.



Cheers

Jonathan