I have some off-brand thing that I bought from TSC several years back, cover is made to look like diamond plate...kerosene/diesal...I just run kerosene in it...have had several of them over the years, and rarely have issues with them, they usually last me till they start to rust out...
biggest thing is to take the cover off at the beginning of the season and blow out any dust/ mouse droppings/smal furry animals, and clean and regap or replace the plug...take a quick look at the fuel hoses and spark plug wire, along with the electricl cord, and your good to go for the winter
when your done using it for the year, repeat the cleaning process to get the carbon deposits and misc dust and stuff out of it, fill the fuel tank (add stabil if you want, I never have, and never had any issues with it), and loosely cover it with a garbage bag or other plastic, and put it away till the next winter.
another thing that seems to help them alot is to get them off the floor about 12-18 inches, so the heat isnt wasted trying to warm up a frozen slab of concrete (once the slab gets cold, its staying that way till spring, unless you can keep a constant heat on it for several days)...I built a small cart for mine, that keeps it protected when being used and stored, keeps it up off the floor, and has an outlet and light switch hooked right to the cart. the heater plugs into the outlet, and the switch turns it on and off, and allows me to run another cord off of the cart at the same time