Hi all, I'm new to the forum and I hope you all can help me make an informed decision.

I am looking for a low cost commuter vehicle and I came across a 2003 Audi A4 3.0 Quattro with 170k miles being sold by a tow company for $1000 so I went to look at it tonight.

The vehicle was towed this summer and has sat on the lot since. The interior and exterior are in fantastic shape; its the motor that I'm worried about.

We jumped the engine and I found that the engine had a terrible knock coming from the left (Driver's side head). I've never diagnosed engine knock before, but it sure sounded to me like a cam knocking as it rotated.

Once I heard the knock I checked the engine oil level: it was bone dry at the dip stick and the oil cap. The radiator reservoir was all but empty as well, but showed no signs of oil mixture, which I hope means that the head gasket is in good shape.

I added 3 qts of 5w30 to see if it would help with the knock - and it did, more than I expected, in fact. With a full belly it might actually not knock so bad at all.

While I was listening to the decreased knock I observed white smoke coming out of exhaust pipe. It smelled like burnt oil to me, though I usually associate white smoke with burning coolant.

This has left me with a number of questions:

- Why were the oil reservoir and radiator reservoir effectively empty? Owner negligence or leak?
- Is there a connection between the empty oil and the knock? Can't be coincidence.
- What was the cause of the smoke?

and most importantly:

- is it worth buying and diagnosing / fixing?

What is the diagnostic workflow on a vehicle, Audi specifically, experiencing these symptoms?

I've read white smoke can be caused by anything from a stuck injector to a defective turbo oil seal (is there a turbo on the 3.0?) to busted intake mani gaskets, head gaskets, or even cracked heads / blocks.

I've read that engine knock can be caused by anything from using low octane fuel, air/fuel mixture issues, or a chipped camshaft.

Being the Audi pros that you are, what would you do in my shoes? How hard is it to work on these things myself? (I've done engine swaps, head jobs, and other engine work myself, but I have heard horror stories about Audis).

TIA