At 26,000 km, the service interval for the F - TYPE is nearly double the 15,000 km interval for the 911 Turbo. (motoring.com.au)
Five - star safety and 36 - month / unlimited kilometre warranties were common, with 12 - month / 15, 000 km service intervals for the Audi and 12 - month / 25, 000 km intervals for the Merc. (motoring.com.au)
After that I would just use distilled water and change it couple of times in 10, 50, and 100 km intervals, until you see, that it does not contain any oil. (mechanics.stackexchange.com)