22 unit 5 story walk up apartment building

I'm currently running a an old steel boiler with about 70 steel tubes x3"".... Running on a carlin 801 burner blasting about 18gph ..... Oil is out of this word these days , I owned this property for 11 years and never have we burned so much oil I'm convinced thes an additive or something in heating oil as of recent that causes it burn much more quickly .... I've had computer testing done this year and we are burning about 84% eff which I'm told is pretty good , now I know the old days of oil at 1.5 ,2.5 are gone but dam I'm thinking of moving to gas conversion .....anyone have an idea of a good equivalent dual fired burner I could slap on this boiler ?..... Thanks JD