[s-cars] Burning Oil

[Fred Munro]

Hi Cody;

On the AAN you've got four main routes to oil burning:

1. oil getting past the oil control ring on the piston
2. oil getting past the valve seals
3. turbo lube/cooling oil leaking past the turbo shaft seals
4. excessive crankcase blow-by (bad piston compression rings)

In response to your question, the piston is fitted with compression rings
(top set) and an oil control ring (bottom ring). The oil control ring is
designed to scrape excess oil off the cylinder wall on the piston down
stroke but leave enough to lube the piston. If the ring wears or loses
tension it leaves too much oil on the cylinder walls and this gets pushed
into the combustion chamber on the upstroke and burned. Some engines have
two oil rings per piston - I don't know offhand what the AAN has and I'm too
lazy to go get the Bentley :o)

Case 1 burns oil all the time.

Case 2 burns more oil under deceleration - you typically get a puff of smoke
when you lift the throttle to change gears.

Case 3 leaks oil all the time but burns more at high RPM when the higher air
flow pushes the oil laying in the intake hoses into the engine.

Case 4 burns more oil under high load.

It is very unusual for the I5 to burn oil. The only I5s I know of that had
an oil burning problem were the NA 20v engines used in the Audi 90.

HTH

Fred Munro
'94 S4

-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com]On Behalf Of Cody Payne
Sent: December 29, 2003 1:51 PM
To: Robert Myers
Cc: s-car-list at audifans.com
Subject: RE: [s-cars] Burning Oil


Hey Rob,
    I had this issue "before" the turbo change so not sure it is turbo
related.  Going to keep an eye on the oil consumption... (RedLine
10W-30) When I removed my x-over pipe for my RS2 EM install I didnt see
much oil in the tubing nor the Samco hoses

If it is in the engine "how" does oil get past the piston rings besides
leaky valves stem gaskets?  Can oil defy gravity and be "pushed" up past
the rings of the pistons in to the compression chamber?  Thoughts on B&G
RF-7 (not sure it works w/ Synthetic oil) or STP Smoke Treatment? (Not
that my car is noticeably smoking)

Thx

cp

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