Has anyone had a problem with excessive oil consumption?

indicates failing main and big end bearings
the clearance is excessive and under heavy loads the oil is passed onto the cylinder walls and the oil ring cannot control it
one fix may be to go to a 30w-50 oil

In the great plan of things simply claiming excessive oil consumption is not enough. You think you know what you mean but how much is excessive?

Car manufacturers insist before taking any warranty action for excessive oil consumption a test must be carried out to decide whether the consumption is excessive and whether repair will be economic. Even though your car isn't under warranty the principle generally will be the same.

An oil consumption test is carried out after a few basic checks and means topping up the oil exactly and then driving 750 miles of mixed town and country driving that doesn't include any sustained high speeds or heavy congested traffic. The oil is then checked and topped up exactly and if the quantity is less than 1 litre it is considered acceptable due to any improvement being uneconomic to achieve.

How many miles is your car covering per litre?

Of course if the engine is producing smoke things are somewhat different...

You had the codes read out at a local parts place? Most will do it free.
Oil has to be going some place. If it's not on the road, then I would certainly expect smoke. The performance may have nothing to do with the oil consumption, you should not assume they're connected. I had similar oil loss, turned out to be a leak in the oil filter, only leaked when on the road, not in my garage.

Yes that is normal, Subaru failed to tell customers of the oil consumption, if you go to your Subaru dealer they will fill oil to level & tell you to come back in 1200 miles time, they use 1quart every 1200 miles

Check or replace your PCV valve.

definitely an oil consumption problem. How many miles? Could be worn rings and or valve guides. The oil light on when hot indicates low level or possible or weak oil pump. Check compression for possible head gasket or cracked head. I wouldn't drive it untill diagnosed.

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Wherever the engine stops there will be at least a couple of valves held open and overnight the force of the valve springs can force the oil from some of the hydraulic tappets (if fitted). Some engine designs can take as much as 20 miles to cease tapping...

Some timing chain tensioners are oil damped.

If noise disappears when you top up the engine oil the clear solution is to top up more often - the engine oil level should never be allowed to fall more than 1 litre below the maximum level and it should never be overfilled.

Locating and curing the cause of excess oil consumption can be expensive and complex and the process involves a certain amount of guessing and eliminating so sometimes it is better, quicker and cheaper just to have the engine overhauled.

The general rule is it isn't economic to repair excess oil consumption unless it exceeds 750 miles per litre of mixed driving that doesn't include any sustained high speeds unless there is smoke when the engine must have attention or be scrapped.

Before testing the oil consumption the engine breather should be checked and the oil topped up accurately.

If there are no visible crankcase emissions caused by excess piston ring/bore wear, the most likely cause of excess oil consumption is the valve stem oil seals - unless the engine is so gunged inside the oil being pumped to the top of the engine can't drain back fast enough...

excessive oil consumption and smoking is usually due to worn rings and/or valve guides in the engine. If you observe blue smoke coming out of the tailpipe, it signals a worn out engine.

If no external leaks, that's what it is. Maybe try to change the oil with a high mileage oil when changing the oil and filter.

I'm afraid, that these conditions don't get better with time.

A replacement motor, or overhaul of the present one is recommended if you cannot pass emissions tests in your area if required by law.

Normal oil consumption for a car is about 1 quart per 3,000miles. If you can calculate how much of a quart low you are per oil change you will be able to tell whether your oil consumption is excessive or not.

2006 C4S Tip, 26,000 miles Now in Porsche dealership having the engine stripped. They are suggesting that one of the pistons is starting to fail. Their diagnostic equipment shows no fault codes but further testing has shown that one bank is having to work harder than the other side. Their prognosis is a new engine. Do not let your warranty expire!!! Also see here: http://www.pistonheads.com/gassing/topic.asp?h=0&f=48&t=731645&mid=154532&i=0&nmt=OPC - Does this sound odd to you?&mid=154532