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A cylinder leak down test would be a good idea, especially if you've already got all the stuff to do one, and should confirm some causes of oil consumption. A quick search for how to stop engine oil consumption found some advice from http://www.aa1car.com/library/oil_consumption.htm

A quick search for how to stop engine oil consumption found some advice from http://www.aa1car.com/library/oil_consumption.htm

 

A cylinder leak down test would be a good idea, especially if you've already got all the stuff to do one, and should confirm some causes of oil consumption. A quick search for how to stop engine oil consumption found some advice from http://www.aa1car.com/library/oil_consumption.htm

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A quick search for how to stop engine oil consumption found some advice from http://www.aa1car.com/library/oil_consumption.htm:

OR, are you using the correct (viscosity) oil? There may be a thicker "summer" oil you could be using.

There is probably, or a wall full of oil additives in an auto parts store to try too (most of which may just "thicken up" the"High Mileage" oil anyway).

Or just trying a slightly thicker oil, even if it's not mentioned in the owner's manual (that may be a bad idea, that may have worked better with much older engines). (These are mentioned in the above "Engine Oil Consumption" linked page too)

There is probably a wall full of oil additives in an auto parts store to try too (most of which may just "thicken up" the oil anyway).


And please check your oil more often! Leaving just 1.5 quarts in a 5 quart engine sounds like it could be doing damage, that's probably what the "rattling" you're hearing actually is. The oil dipstick should indicate when it's about 1 quart low, use it!

A quick search for how to stop engine oil consumption found some advice from http://www.aa1car.com/library/oil_consumption.htm:

OR, are you using the correct (viscosity) oil? There may be a thicker "summer" oil you could be using.

There is probably a wall full of oil additives in an auto parts store to try too (most of which may just "thicken up" the oil anyway).

Or just trying a slightly thicker oil, even if it's not mentioned in the owner's manual (that may be a bad idea, that may have worked better with much older engines).

A quick search for how to stop engine oil consumption found some advice from http://www.aa1car.com/library/oil_consumption.htm

OR, are you using the correct (viscosity) oil? There may be a thicker "summer" oil you could be using, or a "High Mileage" oil.

Or just trying a slightly thicker oil, even if it's not mentioned in the owner's manual (that may be a bad idea, that may have worked better with much older engines). (These are mentioned in the above "Engine Oil Consumption" linked page too)

There is probably a wall full of oil additives in an auto parts store to try too (most of which may just "thicken up" the oil anyway).


And please check your oil more often! Leaving just 1.5 quarts in a 5 quart engine sounds like it could be doing damage, that's probably what the "rattling" you're hearing actually is. The oil dipstick should indicate when it's about 1 quart low, use it!

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Not a desired answer, but with no leaks (to ground or into coolant) it's possible that your engine is just using/burning what some manufacturers would consider a normal amount of oil:

How much is too much?

Audi, BMW, and Subaru stick firmly to the statement that oil consumption is a normal part of a car’s operation. Subaru considers a quart burned every 1,000 to 1,200 miles to be acceptable. Certain Audi and BMW cars’ standards state that a quart burned every 600 to 700 miles is reasonable.

If a driver has to add a quart of oil once per month, that can mean adding up to 7 to 9 quarts of oil between oil changes. Those costs due to excessive oil consumption can add up because automakers more frequently require synthetic oils that can cost upwards of $9 per quart—in addition to the expense of the routine oil changes.

From Consumer Reports "Excessive oil consumption isn't normal - Automakers say adding oil between scheduled changes is acceptable. It's not. Published: June 30, 2015 06:00 AM
Also interesting news video here

And that's for new engines, yours is about 9 years old.

A quick search for how to stop engine oil consumption found some advice from http://www.aa1car.com/library/oil_consumption.htm:

CAUSES OF HIGH OIL CONSUMPTION

Oil consumption depends primarily on two things: the valve guides and piston rings. If the valve guides are worn, or if there's too much clearance between the valve stems and guides, or if the valve guide seals are worn, cracked, missing, broken or improperly installed, the engine will suck oil down the guides and into the cylinders. The engine may still have good compression, but will use a lot of oil.
engine valve deposits
Heavy carbon deposits on the valves are caused by worn valve guides and seals.

Worn valve guides can usually be restored a number of different ways. One popular method machine shops use is to ream out the guides and install thin bronze or cast iron guide liners. Knurling is another procedure that can reduce valve guide clearances. With aluminum heads, the original guides can be driven out and replaced with new ones. With cast iron heads, the guides can be reamed out to accept new valves with oversized stems.

If the oil burning is due to worn or broken rings, or wear in the cylinders, the engine will have low compression. The only cure here is to bore or hone the cylinders and replace the worn or broken piston rings


Correct oil?

OR, are you using the correct (viscosity) oil? There may be a thicker "summer" oil you could be using.

There is probably a wall full of oil additives in an auto parts store to try too (most of which may just "thicken up" the oil anyway).

Or just trying a slightly thicker oil, even if it's not mentioned in the owner's manual (that may be a bad idea, that may have worked better with much older engines).