Propane and propane accessories

Well, heater stopped working last week after sitting all summer. After taking the gas valve out, it was full of black goo. I had to order a valve and replace the generator a bi-metal strip. In ordering the valve I found the the propane dealers didn't know much about their products. One dealer said propane comes from the ground and the refinery puts it in tanks. When I questioned what the refinery does he really didn't know. Then it was the question about the difference between LP Gas and Propane, as far as they were concerned they were the same. Looking up the heater I found that the LP Gas model was more expensive. Dealing with a supplier of heater products they couldn't tell me what the difference was between the valves just that it was a different serial number. I use propane but a LP Gas unit was installed here. He won't sell me a propane valve or even look it up but he will replace the LP Gas valve. I looked up the difference between the gases and it's a big difference. Propane a distillate from crude oil. So it butane which is added to propane to make up LP Gas. The ratio is 60% propane and 40% butane to make up LP Gas. Natural gas is totally different as far as the chemical make up. Natural gas has a lot of goodies in it to make it what it is; methane , which make up most of the gas, 70 to 90%, then ethane, butane, propane, carbon dioxide, nitrogen, helium and hydrogen sulfide. What gets me is how so called professionals don't know their products and why they work like they do. I could see the LP Gas need a product that is more resistant to alkaline gas. It just amazes me that these people like the ones at Suburban Propane here in Placerville just think gas comes right from the ground and it put in tanks. They were the original people that put the heater in in 1985. Why they would use a LP Gas unit instead of a Propane Gas unit, I can only surmise they sold it because it was listed at $100 dollars more then the Propane and Natural Gas units.