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Old 08-06-2016, 02:58 PM   #1
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Increased oil consumption

My car has always burned oil for the 40k miles I've owned it. Usually around 1 quart per 5k miles. However around 5k miles ago this has increased to 2-3 quarts and seems I'm topping it off way too much. My AOS did bomb about 1k miles ago which I replaced but I am still going through oil.

I've researched and the vast majority of Boxsters do not burn oil. So this definitely isn't normal. Has anybody experienced big oil consumption increases due to something else other than the AOS?
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Old 08-06-2016, 03:56 PM   #2
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How many miles on the engine?
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Old 08-06-2016, 04:04 PM   #3
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And any idea how many miles were put on it with the AOS bad?
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Old 08-06-2016, 04:17 PM   #4
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How many miles on the engine?
85k

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And any idea how many miles were put on it with the AOS bad?
From when I heard a whining noise that I thought was a belt/pulley issue - about 7 miles. Which ended up being an air whistle. Then 20 feet once it smoke bombed - shutoff was immediate. But it was doing increase consumption before the AOS went bad too.
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Old 08-06-2016, 05:31 PM   #5
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Does it smoke excessively? That's a lot of oil to be burning in 5K. Try a compression
test, maybe you have some stuck/broken rings? You can check each plug and see if they are wet. Have to ask the obvious, no puddles underneath?
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Old 08-06-2016, 11:41 PM   #6
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According to some experts (Raby / Hartech in the UK), bore wear is the biggest culprit for oil usage, though to be honest, its the bigger capacity engine cars that suffer most. By what I've read, either the bores go oval over time or scoring occurs and high oil usage is the result.

Some of the later 3.6 & 3.8 litre engines suffer scoring of the Locasil coating & pistons which looks like seizure marks along the bores and is accompanied by a tapping noise @ idle which is the piston "rocking" @ TDC.
I guess the only way to identify your oil usage is either a leak down test or a borascope - assuming that you don't have a big oil leak which would be very obvious.
Have a look at Porsche Engine Repair and Service Specialists and see Engine Guide for some interesting - if long & detailed info.
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Old 08-08-2016, 05:49 PM   #7
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Did you change oil brands or weights recently?
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Old 08-08-2016, 07:52 PM   #8
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No smoke and no drips.

Interesting about the tapping noise. My car does do that sometimes (not consistently) but I've listened to everything and it sounds like it's from the rear of the transmission. Can't really figure out what the cause is though.

Always Mobil1 but I do switch between 15w50 and 0w40 for summer/winter respectively. But been doing that for 40k miles and the previous owner always ran 15w50.
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Old 08-09-2016, 07:51 AM   #9
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HaHa Winter in Houston!!! You are changing needlessly in that environment.

AOS OK? that would be my main point of checking if you have no leaks.

Some (many) manufactures don't think you have a problem until you hit 1000 per Qt.

***BMW tells owners it's normal for some of its engines to burn a quart of oil in less than a thousand miles. In a tip sheet to fleet-vehicle operators, GM says normal consumption "can be in the range of one quart within 2,000 miles on a properly driven and maintained vehicle."***
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Old 08-09-2016, 06:27 PM   #10
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I just ran the numbers and I've put in 1.5-2 quarts in 1400 miles. Ugh. Somethings wrong.

AOS is new (1400 miles ago). I've read about new ones can have problems. I'll measure my crank pressure tomorrow through the oil fill.
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Old 08-09-2016, 07:50 PM   #11
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I just ran the numbers and I've put in 1.5-2 quarts in 1400 miles. Ugh. Somethings wrong.
That is a lot of oil use and will create other problems down the road with dirty injectors and clogged cat's.

I would suggest cylinder compression and leak down tests.
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Old 08-10-2016, 04:18 AM   #12
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That is a LOT of oil use.

I did some quick and dirty math and that = about 1/5 (.035 OZ) teaspoon per mile. Seems like a really small amount probably impossible to see while driving, unless someone is following and really looking for it. If this was a 911, I would say you need a valve job as the guides are gone. On a Box I have no idea if this would be the typical repair.
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Old 08-16-2016, 06:14 PM   #13
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Has anybody ever had the crankcase vent valve go bad? I've been researching and it's an extension of the AOS. My intake seems to be oily despite me cleaning it before I put the new AOS on. My crankcase pressure is fine though (5 inches). Still going to do compression/leak down tests though.
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