Some modern vehicles may be sludge monsters-apparently the vehicles are designed to run so hot to increase fuel mileage that conventional, and even synthetic oil, breaks down and sludge forms in the engines. There has been a considerable amount of discussion about sludge forming vehicles on the internet-some cars, vans, and perhaps trucks and SUVs seem to be prone to this sludge formation. Is it possible to extend oil changes on vehicles like these, perhaps using a motor oil like Schaeffer's Oil and a product like Auto-RX? Or, if a person is driving a sludge monster, are 3000 mile oil changes better?