spraying oil together with the fuel will increase the compression, the problem is that the oil will not burn completely, and that will generate carbon deposits and "possibly" at some point the failure of a spark plug. In older diesel engines, it was common to put a little light motor oil in the fuel. An improvement in performance was noticeable, due to the increase in compression, but it generated many carbon deposits on pistons and valves. The riskiest made kerosene together with the diesel and the increase in performance was even more notable….but piston breakages were more common (due to higher temperatures and out-of-control detonations)