Even a cheapskate landlord should be willing to spring for installing a smart economizer control like an
Intellicon 3250 or
Intellicon LCH, or
Beckett Heat Manager, which auto-adjusts the high temp based "learned" responses from burn cycles to anticipate the end of a call for heat. They also heat-purge the boiler down to the (user programmed) low temp before firing the burner on a new call for heat. The net result is that the average temp of the boiler drops, which means the standby losses to the boiler room plummet. The average distribution plumbing temp & losses drop too, but during peak-cold periods everybody still gets to stay warm.
The heat-purge-before firing aspect means that when the loads are low it will "exercise" the thermal mass of the boiler over some delta-T to keep it from short-cycling (something that outdoor reset strategies are prone to doing), but the average temp of the system still remains low for low-loss.
The net fuel savings will be far more than chiseling away hand-tweaking the high temp until the tenants complain. During cooler weather it auto-adjusts up, during warmer weather it backs off, but even during cooler weather the standby losses go way down even if the peak temps are banging on 220F, since it "parks" the system at the end of a call for heat at a temp below the peak temp it reached when firing.
The programmed low-temp limit can be set as low as 130F for most gas fired boilers, but holding the line at 140F is prudent for oil fired systems to avoid damaging condensation in the flues or the boiler's heat exchanger.
20psi is on the high side for a 1-story application- most run at 12-15psi. There is no advantage to running it any higher than necessary.