cliffcoggin

You'd have thought so from the point of view of a practical mechanic, but the "master technicians" that Audi employ can only plug in their computers and read the screens, and if the computer says "no" you are out of luck yet still face a large bill.

Nonsense. You asked a vague question about oil additives. "I'd appreciate any advice out there about oil treatments" were your precise words. That's not a technical question, nor is it framed in the precise terms one would expect from a supposed engineer. And when the replies failed to match your hopes of a magic solution you resorted to accusations of unhelpfulness and ignorance. An old adage comes to mind here: "You can lead a horse to water but you can't make it drink." For an alternative argument consider the matter in a logical manner. If the snake oils you are investigating really worked, do you think Audi would have spent hundreds of thousands of pounds on an engineered solution if a few bottles of thixotropic viscosity modifiers such as polyisobutylene were sufficient?

Jason. I have merged your two identical topics. Please do not create duplicates. You won't get any extra attention by doing so.

Have you progressed this matter Martin?

I repeat "nothing you can do by way of additives or treatments will help". Sorry you find that unhelpful. Would you prefer me to have advised you to spend silly amounts of money on useless materials? It's your money to waste as you want, but don't expect me to condone it.

In that case we need to find a way to diagnose the fault, which is going to be nearly impossible just on written descriptions. Perhaps the best way forward is to get a diagnosis on a different machine. Code readers differ greatly in their abilities.

One possibility is a failing battery. I suggest you get it professionally tested. Do not rely on a simple voltage reading to indicate the state of health of the battery, nor should you rely on its starting ability. If the battery proves to be in good condition we need to investigate other possibilities.

Diesel? You didn't mention diesel until now so I wrongly assumed the fuel was petrol. Diesel does not suffer from pre-ignition so your problem lies elsewhere. Incidentally diesel, being a longer molecule, is measured by decane rating. As far as I know only one grade of diesel is available here, except for the anti-waxing additives in the winter.

For a little while some of the TFSI engines were notorious for extremely high oil consumption. As far as I recall they required re-designed piston rings from Audi to solve the problem. If yours is one of those affected engines then nothing you can do by way of additives or treatments will help. Doubtless that is why the previous owner sold the car. Sorry, but I believe you have bought a lemon.

It's the same problem that you remember from the old days from your description: pinking or pre-ignition. It's the result of too weak a fuel mixture or a spark that's too far advanced or fuel of too low an octane rating. If you are using the right grade of fuel there is a problem with the engine that needs diagnosis.

A worn prop shaft bearing should be easy enough to detect by any mechanic, so it does seem more likely to be the gearbox.

It's a common problem on Audis, and probably other brands for all I know, that the Adblue crystallises in its tank, pump, and lines leading to the lot having to be renewed.

Thanks for the confirmation.

That sounds plausible. What is the other end of the hose connected to?

No. The noise is always worse when turning because the balls have to move further in their tracks.

Where have you looked?

Why? A wise man once opined to me that what man has made, man can repair.

I am not disagreeing.

Pinking, or pre-ignition, is not dependant on engine speed, instead it depends on engine load hence it happens when accelerating. A fuel mixture that is too weak or a spark that is too advanced will cause pinking. Modern engines normally detect that pinking and automatically adjust the ECU output accordingly. That's not to say your engine is definitely pinking because we can not hear the sound, but it is a possibility.

If you are not concerned by the appearance and it does not let in the rain, then all's well.

68000 miles is perhaps a little earlier than expected for an alternator to expire, but not unreasonably so. Get the garage to test the battery when you change the alternator as it may have been damaged by continual discharge. However look at another recent topic on this forum regarding "brake servo restricted" for further enlightenment.

All I hear Hamza is tyre noise. I hear nothing unusual, which is a common problem when recordings are played back. You have become mentally attuned to the sound your car makes. Note that some tyres are much noisier than others, and affected more by the road surface. What happens if you refit the winter tyres and drive along the same stretch of road? Does the noise change or disappear?

Any news to report Ian?

Mark. I see you looked at this forum yesterday, so have you made any progress on the matter?

The warranty would become void as soon as you modify the car.