I have a tapping sound under the valve cover on the left side. It only makes a noise when under light throttle through most of the rpm range. Basically when keeping speed. Push it hard and it goes away.

Something may prevent the valve lifters from pressurizing properly. The lifters could be dirty (How clean is your engine internally?) or oil pressure may be a bit low. Consider changing oil viscosity. For example, if you are using a 5W-30, try a 5W-40 and see if that helps.

Of course, you should make sure oil pressure is within specs. You may also want to make sure the oil check valves in the heads function properely. Another possibility is a defective oil filter bypass or anti-drainback valve.

Its pretty consistant through rpm and temp. Only difference is the throttle %.

<center><img src="http://pictureposter.audiworld.com/87187/oil_specs.jpg"></center><p>They make no reference to 0w40 anywhere.
You can use 20w50 in the summer.

There was lots of valve train clatter at hot idle coming from my 12v when I used M1 0W-40. I did not hear any unusual noise above idle RPM, though. Different oils have different noise dampening qualities. The noise is likely harmless, but can be rather annoying.

Audi did not spec a 0W-40 for the 12v, because there were no 0W-40 oils back when that engine was developed. Your engine is supposed to use VW 500.00 or VW 502.00 oil. While M1 0W-40 meets VW 502.00, it is not even recommended by Mobil for the 12v. Go to the Mobil site and use their oil finder to see for yourself, if you don't believe me.

You say you don't know the conditions inside the engine. Well, you certainly know if the engine is cold or at operating temperature when the noise occurs. Your car comes equipped with an oil temperature gauge. ;-) Knowing when the noise occurs, would really help in trying to find the cause.

and if you don't want to waste the current oil by doing an early oil change, simply add some M1 15W-50 next time you top the oil off. Even half a quart can make a difference. That should thicken up the M1 0W-40 and might reduce the noise. You can mix M1 0W-40 and M1 15W-50 without any problems. It's worth a shot.

for my '96 A6 Avant 2.8L 12V. I've been using that oil in it for some time w/o any noticeable change in lifter noise. I made the switch from using Castrol 20W-50 dino oil tyring to solve a "tick" or a "rattle" that make its presence known somethimes on cold start-up. It never does make this noise when warm or if the car is driven daily. BTW, the car has slightly less than 61K miles.

In the 12v it's less than ideal and leads almost always to higher oil consumption than other oils.

I would also use M1 0W-40 only if I were to do oil change intervals upward of 7,5k miles. This oil is designed to thin out, then thicken up over fairly long oil change intervals. If you change the oil frequently, you are basically running a 0W-30 from soon after the oil change until the next oil change. Whether you mind that, is of course up to you to decide.

If I were you, I'd keep my eyes peeled for the new M1 5W-40, which is designed for gas engines. It does carry the proper VW 502.00 spec. I have not yet seen this oil on the shelf, though.

I'm currently running Pennzoil Platinum 5W-40, and the 12v likes it very much. It also meets VW 502.00. Before I switched to the PP 5W-40, I was running M1 5W-40 T&amp;SUV with excellent results. I posted the UOAs on this board. I expect lower oil consumption with PP compared to M1 5W-40 T&amp;SUV and I also don't need the M1's high TBN.

PS: Mobil's recommendations on their website are based solely on the car manufacturer's approvals and as appropriate listed viscosities. Mobil simply cover their corporate ass that way. This does not mean that some of their other oils are necessarily unsuitable for use in any particular engine! ;-)