Diesel's specific gravity is 0.82 to 0.95. Gasoline's specific gravity is 0.71–0.77. Basing from the SG, diesel stays at the bottom. Gas on top. Correct me if i'm wrong but the two are miscible.

Octane rating is lowered so there is a possibility of knocking.
Volatility is also lowered. Fuel will not vaporize easily.

Diesel in a Gas engine is actually not bad when done in a small ratio but straight Diesel will not burn properly in a Gas engine. but it still depends on the ratio of diesel to gas. ilan liters ba gasoline pinakarga mo tsaka carbureted ba or fuel injected tsikot mo?