"I assume the small bottle supplied with the kit is to keep things safer in the event of a rear collision vs. a standard "gas grille" cylinder? Does anyone know whether there are any internal differences between the two bottles?"
I did a lot of research on cylinders, and found no differences between the 25 and 5 lb ones. However, the 5 lb cylinder should be stronger due to smaller diameter, assuming same wall thickness.
"My pressure is now about 70 PSI about the coldest of the day, and my target is 80 PSI, I went for a refill to up the pressure again, it only took half a gallon ($1)."
Do you have 5lb tank? They have a capacity of about a gallon, and with the new style QCC tank they only fill 80%. So I wonder if needing to add a half gallon of gas meant you were almost empty? I read somewhere that as the tank level drops, the btu's drop off, apparently even at the same pressure. Not sure why, had something to do with surface area and more air in the tank I think.
OK, just found the PDF article I printed off awhile ago, sorry no link on it, it is put out by Insurance Management Associates, Inc. Here it is: "...the lower the level of liquid propane in a cylinder or tank, the fewer BTU's of heat the heater will put out. That's because the volume of air space in the tank increases as the liquid recedes and the surface of the liquid can no longer generate enough pressure to escape the container. When that happens it is called gas-out, and can be dangerous because air and moisture may be drawn through the regulator and into the tank causing corrosion..."
Bottom line, you should refill your tank a lot earlier than you think.
Joe
