A8CT

My D3 with 175k does need a drop of oil between changes and that's been the case over the 80k miles I've owned it. Changes are around 6k using M1 0w40. Recently my wife was driving it and the low oil level light came on. Sure enough it was down a QT. I was due for a change anyway, did that and now about 2,500 miles later it's down again but hasn't tripped the light. Possibly related, I replaced the oil cap about six months ago because the original one was impossible to remove w/o pliers. Once you made the turn to lock it there was no going back by hand.

When I noticed the drop today, there was an area of oil visible under the cap on the valve cover and I saw that before. I don't know if the cap is now leaking a little or this is an indication of a PVC issue and oil is getting forced past the seal. While running, I do feel some downward pressure on the cap if I remove it. My PVC is OEM and less than a year old and does not make any noise (the "Y" suction valve underneath that is also new). Since the consumption is fairly sudden, I think this might be where the problem lies. I did the valve covers within the past six months and the inside of the engine is spotless, zero sludge.

I came across an Audi oil cap that's vented and designed to relieve some pressure. Has anyone tried to see if it fits the 4.2? It's listed for the 1.8, 2.0, 3.2, etc. but not specifically the 4.2. It looks the same in the pictures.

Aside from the PCV, where else have you guys found vacuum issues like this?


Bob

richard-tx

Do NOT put a vented cap on that engine. It will screw up a ton of things. If the PCV valve isn't honking, it will in short order and that is just one thing that will be wrong.

Aceler8

I'm in a very very similar situation...

My car has 174k and needs a little oil between 10k changes, but recently (last week) i did a change and used 1 gallon of Rotella.

Twice in the last week, the 'check oil level' warning has chimed. I filled it first time and last night again. Starting to worry. Will check it in more detail this weekend and report back.

oh yeah, i recently did gasket change and PCV valve change in last 20k miles.

richard-tx

The capacity of the 4.2 engine is about 7.5 quarts or a little under 2 gallons. Are you using 502 00 spec oil?

MP4.2+6.0

FWIW, a head scatcher. Potentially big internal issues, so worth trying simpler stuff. I would replace the oil cap again w/ a dealer one. If suction valve/pump was not OE (I think you were referring to replacing this?), same. Probably dealer sourced previously though? If it was dealer, I would take it out and inspect. Similarly, may need to double back on PCV valve. At least pull to inspect. Of course pul belly pan too if not off already recently in case its a mechanical leak.

After, plug pull and maybe compression check. Looking for a plug that has oil on it. Scenarios then are bad valve stem seals or a piston/block issue. You can try diagnosing stem seals the old fashioned way--shift down on a long descent (or alt least long freeway offramp) to bring engine RPM well up (3 or 4K for starters) and see if it pulls oil out the exhaust. Blue smoke the classic giveaway. Audis used to eat stem seal in the olden days (like 30 plus years ago), but hardly heard of these days.

Having been though this for literally three years on my 2000 A6 4.2, it was quite the wild goose chase and frustration. On mine, I ended up at the worst case scenario--damaged block all the way at bottom of scraper ring area. At that point I put in the wrecking yard piston I had sourced (in case it had been rings/piston), bent and crimped the oil sprayer under it some, buttoned it up and basically ran straight 40 weight. And yes, it smoked. A lot when hot and as it got worse.

Aceler8

i usually don't get that much out using a siphon, but i think you are correct. I only added 1 gallon.

thanks....

MP4.2+6.0

Hmmmm..there are one, make that two clues, maybe three...

• Rotella? How's that 18 wheeler D3 mod going??
• A gallon of the 7.5 qts., and with a suction pump? Sounds like sort of like set up for more wear x 2 to me if done over a variety of changes like that. Won't ask about the filter I guess.
• Meantime, I'll guess maybe belly pan hasn't been off either given suction pump reference? And if not, look for physical leaks underneath w/ pan off--along with a whole oil slick along the tranny and then floor pan perhaps.

Less tongue in cheek, besides VCDS I continue to believe removing belly pan every 10K and really getting under there are probably the two best basic diagnostics around. With my C5 4.2, I had to do it underneath to deal w/ filter. Same w/ (easy) D3 W12 and now D4 4.0T A8/S8.

richard-tx

Get a Mity-Vac and get all of that old oil out of there. My Mity-Vac sucks all the oil out of the pan. I pulled the plug once to be sure and got a couple of drips. The Audi dealer uses a similar machine to suck the oil out.

You can't do quality work with marginal tools.

Tstealth32

Rotella T-6 exceeds the standards we need. I use it, but I'm also out of warranty. Bobtheoilguy has several reports that it works very well in BMWs, Audi's, and VW. And it's cheaper.

richard-tx

If it doesn't say VAG 502 00 then it isn't good enough. There is a reason why VAG says to use 502 spec oil. Use anything else and you are on your own. Don't come back complaining about the terrible cost to repair the engine or how the Audi engineering sucks. The choice of oil was a poor one.

The cost of oil is minimal compared to fuel costs. Premium is about $3 a gallon. LiquMoly 5-30 502 spec oil is $35 for 5 liters. Since you need two, the total cost is $70. 20 gallons of gas cost $60. So your oil costs are minimal over 6000 miles. Your gas consumption is something over 300 gallons (20 mpg) for 6000 miles. So for the cost saving of what, 5-10 gallons of gas you are willing to risk the engine life? Using cheap non-spec oil makes no sense at all. You could save more than that simply by driving less aggressively.