Running oil-fired radiators most efficiently.

Right, yes, I'm back in the USA, but I'm having a hard time finding anyone who can give me good advice on this here.

We are renting an 'old' house here in Maryland (c. 1934). I think the radiators were installed in the 50s. Unfortunately, they are oil-fired and oil is NOT cheap. I've had radiators in the UK but gas fired. My mother has never had radiators so is clueless.

We went through 150 gallons in less than a month. That cost us over $300!! 

It's a big house with high ceilings and an open plan living/dining/sun room. We are sealing most of the windows with the plastic-y stuff and foam taping the doors. We can't shut the system down completely as the furnace also heats the water supply for the kitchen, bath etc. So we can't rely on space heaters entirely.

Here's my question, if we turn as many radiators down as possible, or turn the thermostat way down at night and use space heaters, will that really conserve our oil usage when the system is continually heating water?

Is there anything else useful I should know about using these things?

TIA!

I used to turn them off alltogether at night and put a extra blanket on the bed in cold weather.  I have them timed to specifically to come on 30mins or so before my alarm and off again at the time I go to work...again timed to come on 30mins before I came home.  The weekends were a problem more - I manually turned them off and on again accordingly.

Turning off radiators in certain rooms that are not in use and shutting the doors..also good draught excluders.

You have to be really anal about it...but it pays off in the end. 

Oil is expensive no matter what you do I think. My parents rarely use their oil furnace anymore, and have switched to a woodstove/efficient space heater.  It's a little colder where they are than Maryland, but I've used oil before, and it's not cheap, even using minimal heating.

My parents used to put slate toppers on the radiators to help with heat distribution.  I am assuming you have those big cast iron things.  If there's a lot of houses in the area with these radiators, you might find people who sell finished ones (wood along the sides) at flea markets or whatever.  I would not have unfinished ones with kids or pets.  I think they make them out of other stones, and at least according to this blog, it appears there might be mass produced somewhere by someone.

If you live in an area that gets dry in the winter, a pot of water either on the stove or set on the radiators not only helps with dryness, but makes it feel warmer. Making sure your storms are closed, and if you don't have storms, covering them with plastic sheeting or with thick thermal curtains will help. It's really surprising just how much storm windows help, and if you're not used to them, you might not realise it.  Plastic sheeting looks ugly, but it helps somewhat if you don't have storm windows.