Boiler insulation

Probably a dumb question, but do people ever add additional insulation to their boilers? I know people wrap hot water heaters. My basement gets pretty cold in the winter.

My small Dunkirk Empire II cast iron oil boiler appears to have a few inches of fiberglass batt inside the sheet metal housing. I'm wondering if I could save fuel by adding additional layers of insulation to the outside of the housing. Rigid foams are probably a bad idea because of flamibilty and smoke generation, but compressed fiberglass or mineral wool with a non-combustible extrerior finished surface might be a possibility.

I don't see any air intake louvers on the housing. Is there a risk starving the boiler of air?

Is this a stupid idea?

What about just bunging up any holes on the housing? I feel heat loss at these locations.

Any thoughts on this?

There are safe and simple and effective ways to save on your heating bills, this is not one of them.