Isuzu Repair: auto hoses, auto parts store, pressure fuel

Question
My repair shop noted my hoses(Radiator, Gas line, others should be changed. My car is an 2001 with 89,000 miles. Stated part of the cause of the deterioation of the hoses was reformulated gas addatives.  How can I tell, say a radiator loweer/upper hose is in need of changing. How can I test them. They look O.K & do not appear to have cracks. What is the gas line make of? It seems to have a rubber outer housing. Any advise is appreciated as he wants $400/$600 to do all the hoses.  Thanks

Answer
Well Bill. All rubber hoses are supposed to be changed every three to four years. The best way to tell if they are bad if there is any swelling or split ends. Or the hose will be collapsed in certain places. The rubber hosing on the gas line is a special high-pressure fuel injection hose yuo should be able to buy at any auto parts store. Although it is kind of expensive if you buy alot of it. There is no way to just look at a hose and say if it is okay or not. You have to feel and test them under your engine and the pressure it puts on them when running. Any more questions I am here okay Bill?