Keeping a GTI reliable is mostly about not stretching the service intervals. VW's long-life schedule is easy on paper and hard on the car.
Oil. VW's long-life interval (up to about 10k miles or a year) is too long for a turbo GTI driven hard. I change the oil every 5,000 miles or so, with the correct spec: VW 502 00 full-synthetic for the petrol turbo engines (check your engine's exact spec). Short intervals keep sludge at bay and protect the chain tensioner.
DSG. Fluid and filter at about 40k miles. Do it on time.
The other intervals I keep:
- Spark plugs: about 40 to 60k miles, sooner if the car is chipped. Set the correct gap, or they kill coils.
- Brake fluid: every 2 years.
- Cooling: I treat the plastic water pump and thermostat as a wear item.
- Carbon clean: about 60 to 80k miles on direct-injection engines.
- Haldex fluid applies to the R and 4Motion cars, not the front-drive GTI: about 40k.
So halve VW's oil interval, service the DSG on time, and a GTI is cheap to own.