[ainarssems]

I am using Quantum Longlife III 5W30 but changing it annually anyway which is 10-12k on A6 and 3-4k on S8. There are no problems resetting service remainder with VCDS and You can put whatever mileage/period you want till next service. I set it for 15k km and 360 days whichever come first.

I got the Longlife oil for £22.50 for a 5l can so it is not that expensive and can be had cheaper if you buy it in drums. And at least I know I am driving with the oil specified and used by manufacturer.

The problem with longlife oil driving little distances is that while engine is cold some of the fuel does not evaporate but end up on cylinder walls and is drawn down by piston rings and end up in oil diluting it. This is more applicable to diesel engines as diesel then evaporates from oil very slowly once engine is warm but affects petrol engines to some degree as well even if petrol evaporates better. Diesels with DPF are even more affected as in DPF regeneration cycle some of the diesel end up on cylinder walls even on warm engine.