Oil and Coolant Consumption
 

2006 CS has about 22K on the odometer. I purchased it with 10.7K on the clock. I drive it daily (about 75 miles/day). I have not tracked this car yet but I do not baby it. At about 18K I noticed the oil level dropping a little more rapidly than I'd like. I also noticed coolant level was low. Coolant took about one quart to bring to the min level.

I just did my 3rd oil change (0-40 M1) a couple weeks ago and it has dropped one quart in 450 miles. Coolant level is also below min level again.

I always cut oil filter open and inspect. To date the filters have not shown anything.

Also, at around 18K I've noticed the exhaust tip was really sooty.

There is no smoke at start-up or upon hard acceleration.

Do you think an AOS could be the cause at 22K? Or do you suspect something more serious?

thanks

Not sure if you want keyboard mechanic speculation or serious diagnosis.
I'll go with diagnosis:
There is a simple test for a failing AOS. You test the vacuum at the oil filler cap with a manometer of your hand.Lots in Search.Your local Indie would do that in a few minutes.
Sooty exhaust- is it unburnt fuel or oil ? CEL ?Tailpipe test for HC?
If there is oil consumption ,is it leaking or using /If it is using you need to give a specific rate of use for a useful opinion.If the AOS is failing ,that would cause it.So start with that and be aware of the problems with replacement AOS units .

IIRC, the Owner's Manual states the oil consumption limit as 1 liter per 1000 km (or 1 qt per 586 miles). Thus, the oil consumption of 1 qt per 450 miles is definitely high and over the factory limit.

With use that high, I would investigate to find where its going...

Well both oil AND coolant are low...
If it were just oil or just coolant, lots of possibilities. Coolant gets high, then oil in coolant, oil cooler?

Oil could be AOS, coolant is either leaking in the trunk or leaking through cracked cyl head or head gasket.

Not enough info:)

I would suggest three tests:

1. Get the AOS vacuum level tested.
2. Pressure test the cooling system.
3. Run a leak down on the engine.