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Topic Review (Newest First)

  • 08-08-2007, 09:51 PM

    Re: oil consumption

    I have a 1988 535is with 260 000 klm ,160 000 m it uses about 1qt per 5000 ,i use only synthetic oil.
  • 05-23-2007, 02:44 PM

    Re: opps.. stupid enter key

    Blow-by from combustion pressures past worn piston compression rings pressurizes the crankcase, forcing oil vapors back up through the cylinder head and over to the intake plenum via the breather tube. The crankshaft does a pretty good job of creating an oil cloud that can get carried upwards. There's a drain hose from the plenum back to the sump for most of it. I usually see a bit of oil on the bellows from the AFM to the plenum. I've also seen it on most of my other fuel injected cars.

    Our cars don't have a PCV system in the normal sense. The crankcase just vents to the near-atmospheric pressure plenum upstream of the throttles. There isn't a PCV valve in the system. Traditional PCV systems vent to the intake manifold downstream of the throttles where a vacuum exists.

    As for clearances, theres no doubt that things open up over time. But our '88 has burned/leaked/? oil at about 1,500 miles per quart since we bought it at 12,000 miles. It's somewhere around 178,000 miles now. I'd like to think that Mobil 1 has something to do with it.
  • 05-23-2007, 01:00 PM
    Bruce in Canada

    opps.. stupid enter key

    The oil in in the crankcase and is pumped to the cylinder head to libricate the valve train.

    Oil can leak past the valve stem seals and burn in the combustion chamber and go out the tail pipe.
    Oil can leak past the piston rings and also enter the combustion chamber and burn.

    but I dont think that the oil can get into the combustion chamber and then somehow go up stream in to the air intake.

    I think that the PCV system can introduce oil air into the plenum/manifold. so the question is how is the air getting so oil?
    I dont have a good answer, but if the crankase vapours are too oily, then maybe the type or grade of oil is wrong? some cars have an oil separator in the PCV valve, but ours does not.

    Maybe someone knows why the intake can get oily on some cars.. I am fairly sure it is not from Blow BY...
  • 05-23-2007, 12:54 PM
    Bruce in Canada

    not sure where the blow by is?

  • 05-22-2007, 11:23 PM

    Older cars, high miles.., loose clearences

    I think we are just suffering from old car / high mileage syndrome. My car has 270k with a new head and still burns a quart every 1500 miles. The plenum is the tell tale sign... full of oil from blow by.

    We all just have to live with it until we rebuild the engine.

  • 05-18-2007, 11:55 AM
    lkfoster in canada

    same here

    For the most part I've used a quart every 1,500 miles forever. Sometimes it's a lot fewer miles, but I haven't sorted out why.

    I had an oil return tube leak too. It must have been there for quite awhile, but it never dripped onto the ground so I didn't know it was there.
  • 05-17-2007, 06:42 PM

    Re: oil consumption -- update

    I did some snooping around and found 3 places I am leaking
    1) rear oil return tube (near the exhaust rear of block to head)
    2) tensioner
    3) striped and now missing bolt on rear of oil pan. pretty minor

    the exhaust side of the block is fairly well coated with oil, so I am hoping that taking care of these items will significantly reduce my consumption.

  • 05-15-2007, 01:32 AM

    Re: oil consumption

    Sounds a bit high but if you have a leak there's no way to tell for sure. I burn about a quart every 1200 miles.

  • 05-14-2007, 10:20 AM

    seems high to me

    I find that my M5 needs to sit for A long time for the oil to settle in the oil pan. more than the time to fill up with gas.
    I would check it in the morning, before starting. That is the only way I get good reading.

    I would really make sure that your OIL LEVEL sensor in the oil pan is working. It is way to expensiv an engine to run low on oil

    That sensor should be set to a level that will protect the engine. Not a big deal if it comes on.. just top up right away.
  • 05-13-2007, 07:57 PM

    oil consumption

    So I am monitoring my oil consumption and yesterday on a 120 mile trip I lost approximately .5 quart. I drove fairly conservatively...highway driving. No hard accelerations, but I did cruise at 90 - 100 mph as conditions would allow. I have a small oil leak, but my exhaust looks clean after the car warms up. I have no real tell tale oil burning evidence coming out of the tail pipe. Generally the car runs nicely (except the sutter on de acceleration that still persists ... err).
    Does anyone have any clues on this? It seems more than acceptable to me. I am hoping to do a 1000 mile trip next weekend and don't want to pack 10 extra quarts for the trip (but obviously will). I am running mobile 1, which some say sneaks past seals and such more than dino. Could this be it, or am I looking at more? Recall...I just put on a new head, but I am now wondering if the valve seals could be suspect because the head did still for a while before installation (though I lubed the hell out of it before my very gentle cranking session).


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