Disappearing Oil Leak

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Jan 23, 2003
My family inherited a rather mistreated 90K Toyota Tercel. It had lots of dark sludge in the oil filler cap and black sediment speckles on the dip stick. It also had an annoying oil leak from the area of the crankshaft to flywheel seal.

I gave it Mobile 1 10W 30 for a few thousand miles then Mobile 1 5W 30. Curiously the oil leaked stopped completely after the change to 5W 30. This seams counter intuitive. Does anyone think that there is a connection or is it a coincidence?
Perhaps the synthetic oil cleaned up enough of the internals to break loose some crud that migrated to the leak and plugged it up, like platelets in a wound.
That's a common effect. I've seen several high mileage vehicles develop leaks after switching to synthetic oil, then slow and stop within a few thousand miles when the seals swell.

i wish i can use synthetic in my 91..yet with a synthetic blend it leaks..but with normal oil it doesnt...heheh guess its dino from now on...
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