We purchased a PDC-4-2500 compressor from PDC Machines in 2006, and we have put 2000 hours of usage in it with minimal maintenance (I.e filters, oil changes). We replaced a Hamworthy Compressor which needed service every 100-200 hours; during one-year span we spent $ 30,000 on maintenance. The other thing I would like to point out is the customer service aspect of PDC Machines, when we have questions, we wait no more than 24 hours to get our answers with most answered immediately. In 35 years in the compressed gas business I have never felt as satisfied as I am with my PDC Machines unit.