timindp

ok, well my A8 has 123,000 and it is starting to burn oil. I smell it when getting off the freeway and coming to a stop. Also, when I start the car in the mornings, I do see blue smoke from the exhaust. Is it time to throw in the towel on this car or is it really worth fixing?

MP4.2+6.0

Can be as simple as the PCV related system that is erroneously sucking oil in excessively. Relatively inexpensive. Need to diagnose.

Could be valve stem seals (maybe just a specific one rather than all). Very hard to do in car w/out removing head, but just barely still do-able w/ the right tools. Expensive/labor intensive (seals themselves are like a dollar--it's all the labor, likely head removal etc.) BTDT on my 2000 C5 4.2.

Or, the very bad scenario--worn rings generally, or maybe a specific one broken. Pretty much a motor pull and rebuild at that point.

First few things you can do are:

Try the "decel test. Go down a long grade, or at least down a long straight freeway ramp. Shift down several gears. If you see a cloud of blue smoke in the rear view mirror, it's likely rings or perhaps bad intake stem seals generally and you pretty much know there's a big issue. If not, try other things:

pull plugs and see if one or more is oil fouled or obviously "wet" with oil. If you are seeing blue smoke, likely so. That can allow you to narrow down which cylinders it is. Obviously the full misfiring engine would tell you a plug is fouled too, which happens w/ serious oil burning issues.

When plugs are pulled, do a compression and (related) leakdown test. That will get at bad rings, assuming no bent or mis-seated valve.

Besides this, you can of course go for the easy partial fix for now. What oil are you using? If a 0W or 5W anything (0-30, 0-40, 5-30, 5-40, etc.) Give up that immediately. Go to a "high mileage" oil (likely at least a 10-40) or if in moderate climates a even a 15-50 or 20-50 . That should reduce the burning. If you are in below freezing weather (or during the winter), probably don't do higher than the "10's" for cold start if possible. Here in CA, in the pre-fuel savings days even dealers 20+ years ago would often just use a 20W 50 all the time. Certainly with oil burning and if not fixing the issue, you would want to go to a higher viscosity oil in general. That alone can cut the oil burn and smoke rate meaningfully.

Net, at least do the decel test and plan to switch to a higher viscosity oil. Neither costs anything really, at least as part of oil change cycles.

timindp

Thanks for the input. I use synthetic 10-40 oil. It starting doing this when I got up to the mountains in Mammoth. The weather was cold, colder than here in Southern Cal. I will look at the spark plugs and possibly try a higher # on the oil on my next change. I just replaced the PCV valve, so I am thinking more along the lines of the seals or valves.

mishar

+1 on what MP4.2+6.0 said.

I would also suggest that you measure how much oil you have to add per 1000 miles. It can be insignificant. In that case you can drive her for quite some time before doing anything. May be just check for an oil leak. It can cause smell more likely than oil burn.

Bangerla

If you are smelling the burning oil when you get off of the freeway, I would be more inclined to think you have an oil leak somewhere. My 99' A8 had an oil leak, and you would smell it when stopped, since the smell would get sucked in through the hvac. When moving you wouldnt smell it. Check under the car, and see if there are any oil spots on the exhaust. Could be that the pcv valve that was replaced has a hose loose?

MP4.2+6.0

Yes, it could be an oil leak too as part of the smell, but (blue) smoking on start up says engine internals most likely to me. The coast down test while shifting down will help sort that out.

MP4.2+6.0

is just a winter fun run, think about 15W50 or 20W 50. You can get synthetics in either. Or even still in 10W 40, the high mileage labeled oil additive packs should help w/ oil burning some.

If you are between changes, frankly some of the MotorMedic/STP type oil thickeners can help pending an oil change next time you need to add oil. No doubt D3 A8 sacrilege, but as my A6 4.2 has edged up to its 14th year now, all's fair to keep it running for cheap--as in, BTDT. I'm in SF Bay Area, so we likely see similar real world driving conditions and temps.