Since July 1999 some Volkswagen vehicles have qualified for extended service intervals (ESI). They are only possible in conjunction with the use of appropriate fully synthetic long-life engine oils. Depending on the engine and model variant, service - and thus oil change - intervals can be extended to as much as 30,000 kilometres or a maximum of two years for petrol engines and 50,000 kilometres or a maximum of two years for some diesel engines. The PR number "QG1" on the vehicle data sticker indicates whether a vehicle qualifies for extended service intervals.