I am on my second mk5 GTI , picked it up in August. Reliability wise they are ok. On my first one, I sold it 6 years ago with 80,000 miles on it . While I owned it , it needed a new thermostat and new instrument cluster as the key kept losing its signal with the immobilizer, and the immobilizer would become active. I had the keys replaced and recoded twice and the problem resurfaced. I eventually had to replace the instrument cluster at a cost of around 700 pounds.
My second mk5 I purchased in August with 6 previous owners and 114,000 miles on the clock with partial service history. When I got it the thermostat was faulty as it was heating to 70 degrees and not the usual 90, same problem as in the previous GTI. Other than that it has been pretty reliable with the 5000 miles I have put on it. I'm getting about 400 miles to a tank with mixed driving, 40 mile round trip to work with 80% motorway too. This was about the same in my last mk5 GTI and pretty much identical to the mk7 GTI PP I had too.
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