Just recently i blew a head gasket, so i had plenty of water in my oil. I drained the oil, and put in new. All was good untill yesterday i noticed my pressure was alittle lower than normal, and my oil light would come on around corners (im guessing from the oil shifting from side to side in the pan). I checked the oil and i couldnt even see the oil level due to the creamy matter covering my dip stick, after wiping it off, i stuck her back in and the level looked really low, not even a quarter of an inch on the dip stick. My pa suggested putting marvel mystery oil in for a little bit then changing it again to remove the water. Any suggestions why my oil might be low? At idle the pressure is about 12 psi . I dont see any spots where i park, at home or at work.

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Drive it like its stolen, and be glad im not YOUR son...

Marvel Mystery Oil, being an oil, won't really clean out water. Also remember that it's probable you didn't actually get "water" in the crankcase so much as you got coolant, which is water plus Ethylene Glycol. That combines with oil to make a very tough gunky mixture to clean out of the crankcase. This is pretty much the only situation in which one of those Butyl Cellosolve "engine flush" compounds, used very carefully, can be beneficial.

Nevertheless, they can't just be dumped into the crankcase without risking severe engine damage. The safest way to proceed is to drain the oil, replace the filter, install four quarts of new lightweight oil and one quart of flush, run the engine at a moderately fast idle speed (1000 rpm) until it reaches operating temperature, drain the mixture, then flush out the flush stuff with a new filter, four quarts of new lightweight oil and a quart of Marvel or Rislone run in the engine at 1000 rpm for 10 minutes or so. Then change oil and filter again, using five quarts of your regular grade of engine oil.

You'll need to keep a careful eye on things -- if you continue to lose oil and/or show foam and gunk on the dipstick, you've still got a coolant/oil leak path that'll need to be fixed.