I just read a story on using diesel oil for gas engines in a car mag. The learned professor of slippery stuff said diesel oil has much greater amounts of detergent and other anti-fouling agents to counteract the foul things in diesel fuel. He said you could keep your gas engine very very clean by running desiel oil which, except for the aforesaid cleaners, is the same as gas engine oil. He especially recommended it for cars that see low miles.
However, if the gas engine is carboned up then beware, using desiel oil will likely cause it to spew great chunks of gunk that was happily residing on the interior of the engine.