Short drives and infrequent oil changes are two factors that lead to formation of sludge in an engine. This gelling of the oil can cause premature engine failure. Oil change intervals depend on the type of driving done. If most of the driving is open highway with little stop and go the interval could be 5000-7500 miles. But if the driving done is short trips and or stop and go, the oil should be changed every 5000 Kms or 5 months whichever comes first. Some vehicles use a monitoring program that lets the computer say when to change the oil. Every oil change includes a multi-point inspection, top up of fluids levels and set tire pressures.