Fuels today have all kinds of cleaners added already. Never heard of adding diesel in the gas tank. It IS common to pour a tiny amount of diesel into the spark plug holes of an engine that is tight from sitting for many years. Diesel fuel is oil and it will dissolve the rust between the cylinder walls and piston rings.
Diesel fuel also burns much hotter than gasoline, (not a good thing in a gas engine), and it requires higher temperatures to ignite. Stick with a good quality gasoline and no other additives will be necessary. I'm approaching 385,000 miles on my '88 Grand Caravan and have never added a single chemical to the gas, oil, transmission fluid, or power steering fluid.