My 2005 MCS coupe burns between 1/2 and one quart of oil every 1000 miles. It's always used some, enough that I noticed it and kept it in the back of my mind, but it's probably getting a little worse lately.

Otherwise it runs fine. 65,000 miles. Gets 30+ mpg on the highway, 26-28 around town. No obvious performance issues. No leaks. No obvious black exhaust. I followed all the precautions when it was new and never got over 4000 rpm until whatever the suggested mileage was.

Anybody have any ideas? What's the worst that could happen if I do nothing except keep topping it off every 1000 miles?

 

You sure there is no blue smoke from the exhaust? Have a buddy watch from another car as you hammer it.

 

Check the coolant too, could be a cracked heat exchanger, though I suspect you would have already overheated if so was the case. If the exchanger is cracked the coolant will look like peanut butter.

 

Unscrew the PCV check valve and make sure it operates smoothly by pushing against it with an allen key. Fixed mine today that was jammed open and causing a high vacuum in the engine and sucking a large amount of air through at idle let alone over run. Once sorted the valve moved freely and the vacuum was much less.

 

I bbq my bearings because of this.
2000$ damage.

Have your oil level above normal!!!

 

No, not completely sure. I've always had black gunk build-up on the chrome exhaust pipe tips. Maybe that's a sign of this.

The coolant in the overflow reservoir is dark green, getting about to the point where it needs to be replaced/flushed, but it's not like peanut butter.

I'll have to take a look. Would this really cause excessive oil use?

 

Yes..... when you lift off your engine can become as low as -11psi and will suck up a huge amount of oil especially after you have been flooring it at high revs when the oil mist inside the engine is thick.

Black on the exhaust isnt really a sign as mostly its carbon and half burn fuel.

Just have to check the options as its got to be going somewhere. Hopefully not the Oil rings but then a blocked breather can also cause that too.