2009 C4S approx 32k miles.
Bought used (not CPO) last December
I can no longer deny the fact that the car has very high oil consumption.
On the average I need to put in 1/2 quart every 300 miles.
Any suggestions?

 

Does it smoke at all on startup?
Does one side of your exhaust soot up but not the other?

If no to the above then try a thicker oil, maybe 10W-50 and get your bores inspected.

 

That much oil, has to be going somewhere. Need to have it checked out. My 06 with 46k miles, burns about 3/4 qt in 5k mi.

 

That sounds excessive. My 06 needs less than a quart between 5k oil changes. I've heard the dfi engines burn more but that can't be right.

 

That seems highly unusual. I have a "top off" every thousand+ miles (guessing) with regular spirited driving and start and stop city driving which will all impact consumption.

You should have it checked out.

Dave

 

How long have you owned it? Has it done it since day 1? That sounds way to high, something has to be wrong, hope it is something small and easy to fix.

 

It does not sound high.....It is high.

Most manufacturers claim that 1 qt/1000 miles should be considered normal. Yours is at 1 qt/1k miles.

I wonder if you even could pass smog.....assuming that your state has smog requirements.




EDIT:
I just noticed you're in SF. Did you pass smog?

 

I'm assuming you're measuring the levels correctly? Do you get a max reading after you add the half quart? Maybe you're overfilling? Are you seeing one bar low after 100 miles or does your reading just go from full to 2 bars down at 300 miles?

 

I basically add 1/2 quart every time I reach 1/2 in the oil meter
But then again it never goes the all the way up to full

I have no oil drips on the garage floor, the exhaust pipes are black during my daily commute driving (lots of stop and go) and have a nice brown color after a track day. The car does not smoke on startup and does not smoke at idle
The dealer did the smog in LA where I bough the car.
Can anyone suggest a better way to track oil consumption than the one I am using now?

 

There have been reports of high oil consumption. However I'd want to know if the e-measurement is working correctly. You say you add 1/2 quart when 1/2 quart down but don't get a full reading - that would worry me. I'd also suggest a complete drain and fill - at least you'll know you started with the correct amount and then start keeping track again. Good luck.

 

That is exactly what I would do, I am not expert, but I do know overfilling is NOT good.

Wish you luck!!!!!!

 

My '09' used oil, a quart/2000? However, my '11' GTS doesn't use any. I believe some of the '09' models used more oil than others.

 

my 07 C4S w/47k doesn't burn any either. I agree with a complete oil change and verify the electronics are correct.

 

The best way to track oil consumption is to ensure you measure the amount of oil in the engine accurately and consistently. The amount/level can vary due to the car being on a slope, the engine being cold, warm, or hot when the measurement is taken.

And measure the oil over time. The classic case of oil consumption misdiagnosis is to drive the car around for a while then hit the road hard and heavy.

The hard usage ups the oil temp and keeps it high for a while, much longer than it has been for maybe thousands of miles and months of driving.

Then the owner notices the oil level has dropped from probably its full level it was before the hard usage.

The owner adds oil and extrapolates the oil consumption based on this one topping up.

Of course the real problem is the engine was using oil all along but unburned gasoline and water kept the oil level up. Then when the engine got used hard and was kept on the boil (so to speak) for a long time (so to speak) this boiled away the unburned gasoline and water.

The result is the oil level dropped dramatically.

All engines use oil. Some obviously use more or less than others. In some cases of "zero" oil consumption there is the very real possibility the build up of unburned gas and water is keeping the level artificially high.

As an aside, early in my Boxster ownership experience I had my Boxster's oil analyzed, this during a mid-western winter. After less than 5K miles of service the water content was 7%. That's a bit over 1/2 quart of water in 9 quarts of oil. These engines are cold blooded and in cool and cold weather will accumulate water in their oil like Lindsay Lohan accumulates court appearances. This analysis made me aware of this water accumulation and prompted me to follow a 5K mile oil/filter service schedule to avoid running oil that had a big build up of water in it.

If the amount of oil your engine is using is real there's not much you can do about it unless there is some warranty and you can document the oil consumption is worse than the owners manual allows for and thus get this dealt with under warranty.

I note while the oil use is high it is still within the guidelines of what is given in the owners manual.

Last, but not least, not to get your hopes up, but I suspect that in cases of high oil consumption yet the engines do not show the symptoms arising from oil consumption due to ring/piston/cylinder issues, or valve stem/guide and seal issues, or even the new models' rumored Achilles Heel the infamous bore scoring (You can't believe how in some regions this bore scoring scare has some owners so scared they are considering do all sorts of crazy things) the real culprit is the AOS.

Now this is just a theory of mine and I wouldn't advise you to run right out and have the AOS replaced.

My best advice is to if you are concerned about oil consumption take the time to accurately determine if this is real or just an abnormal event.

Consider changing the oil more often. As the miles add up as the oil gets more contaminated it is more fluid and thus better able to make it out of the engine via the rings, valve guides, etc.

This more heavily contaminated oil also loses some of its lubrication capabilities so you're doing the engine a favor regardless if the consumption is affected.

Do not overfill the engine with oil. You might consider running the oil level a tad lower than at the max line but don't go overboard and run the oil way low. If you elect to run the level a bit lower of course you need to keep a closer eye on the level to avoid the level going too low.

Avoid using the car in such away that promotes oil consumption. Prolonged idling and sustained high rpms both work to up the oil consumption.

Try a different oil. Always my advice is to stick with a recommended oil but say you're using 0w-40 try 5w-40 or even 5w-50 (not a typo for 15w-50!) provided the ambient temperatures in your area do not make a 5w-XX oil a suboptimal viscosity choice.

Last but not least, and this time I really mean last, relax.

The engine is not exhibiting any untoward behavior, starts fine, runs fine, doesn't smoke or otherwise act up.

So maybe the engine uses a bit of oil. Do not let reports of other owners with tales of much less oil consumption spoil your enjoyment of a very fine automobile.

 

@Macster:

Wow, thank you *very* much for this elaborate and insightful response! I will follow your advise and will also stop panicking until I really have a better idea what's going on and what the real oil consumption is

Many thanks!