Apologies to the OP for hijacking this thread, but in answer to the above my brother is a Process Operator for a major UK oil refinery, and he knows a fair bit about petrol and diesel, and what goes into refining it from crude oil. It is true that the base stock is the same for 95RON, 98RON and diesel regardless of where you buy your fuel from, and all conforms to the relevant BS standards, but the end product consists of far more than just the base stock.

Each fuel company adds their own additves to the fuel after is has left the refinery, and it's these additives that enhance engine performance, clean and decarbonise injectors etc.

Supermarket fuel is often a couple of pence per litre cheaper than branded fuel. You can either conclude that Mr Asda and Mr Morrison are feeling generous and like to do the consumer a favour by saving him a couple of quid, or that the branded product is superior and therefore costs more. I know which one I believe and which one Skidpan believes.

Additives may be added before the fuel leaves the storage depot, but not before it leaves the refinery. Also do racing cars use supermarket fuel? Probably not. You say your cars haven't suffered any loss of performance having run on supermarket fuel, but more likely you just haven't noticed it. One tank may not be that noticeble, but over time it could be very noticable.

My old car, a 2003 Skoda Octavia 1.9TDi ASV engine most certainly did lose that bit of edge when running on Morrisons fuel. Over time I noticed that it just didn't perform quite as well as it used to, but I didn't know what it was at the time. I plugged in VCDS and checked the performance of the MAF actual value against the ECM expected value and nothing untoward showed up. I did the same with the turbo boost pressure and EGR duty cycle, and pump timing base setting. No faults or inconsistencies were found and so I couldn't establish what it was. In the end I decided to use the local Texaco station rather than Morrisons, and within a couple of hundred miles its performance was back to as it used to be, leaving me in no doubt that branded fuel was better. A work colleague with a V8 Range Rover told me he experienced exactly the same, and was also in no doubt. Nothing major, just that little bit of extra zip.

I don't. For me, science trumps philosophy.

For me the proof is in the pudding.

I've driven lorries for a lifetime, these days with Gucci oils our 5 year lease lorries are sometimes needing engine rebuilds by 1m k's,

(our 62 plate German lorries came off the road for bottom end work at 12 months when they found ''apparent contamination'' in the oil, in truth probably another VW group non recall),

the rather better serviced Cummins of 70/80's vintage i drove would cover 1m miles easily and showed no appreciable wear.

Also on those overmaintained:-) engines in all those miles a turbo failure was simply unheard of, fast forward to today and they're stupidly regular.

Not as any of this matters, i'll do it my way and you'll do it yours, i suspect either of us could suffer massive engine failure through no fault of our own at any time...probably you first...:-)))))

One could argue its in a makers interests for vehicles not to last indefinately, some probably learned their lesson with the superb late 80's and 90's designs, they won't make that mistake again.

I do love how everyone goes on about 'modern' synthetic/longlife oils, and how wonderful they must be.

Funnily enough, it seems to be the same people who HATE 'branded' premium fuels, insisting that they're no better than cheapo supermarket stuff.

There is a slight discrepancy there. In one respect, they're denying any advances (fuel), but in the other respect, they're claiming wonderful technological advances (oil)

As I said, I worked at a major refinery location for a number of years (12 years, actually), and I worked in oil R&D during all that time. I don't any more, as, eventually, I grew to hate the commute. There was also talk about the R&D work being moved, and I certainly wasn't going to re-locate.

So, my (knowledgeable) viewpoint is this, as previously stated : Change your oil and filter every 10k miles / annually, whichever comes first. In addition, ensure the old oil is removed via the sump, NOT through siphoning from the dipstick.

If John F or anyone else would like to refute that, then feel free. But let's see your background too, to actually see if you know what you're talking about, or if it's just some random spouting off.

In addition I have had 3 Audi's previous to this car but the youngest had 56k when I purchased it. I ran them all on long service and didn't have a single fault on any of them. My 'N' plate A4 1.8T managed 156,000m with nothing untoward apart from an exhaust manifold change.

My 56 plate A4 2.0tdi avant got to 120,000m and I'd changed nothing apart from filaments that wasn't in the service schedule.

... why would audi risk having to replace an engine and turn down £159 quid for an interim service if you guys are all correct?

You don't have to fork out that much for just an oil change, which is all you are after. If that is what they charge, take it to an independent and make sure he uses the recommended materials to preserve the warranty. There are plenty of indies who specialise in VAG.