Synthetic and oil level reading

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Jan Fure - 11 Jul 2005 19:06 GMT

Since I filled my 1991, 750iL with Mobil 1, 0W-40, the low oil level
alarm has started going off when the (overnight) dipstick level is 1/4
of the way down from the high mark.

I have heard that synthetic oil "clings to the surfaces", and thus
takes longer time draining to the oil pan compared to conventional oil,
and this seems like a confirmation of that. It probably takes 6 hours
to get a repeatable oil level reading, prior to that, the level slowly
increases.

Has anybody else seen this, and if it is true that synthetic oil drains
down slower, would the optimal oil level be higher than for
conventional oil, or would the risk of overpressure exist during
startup?

Jan Fure

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Scott - 11 Jul 2005 23:36 GMT

I have never heard that synthetic "clings to surfaces" and takes longer
to drain but I do know that synthetic oil will sneak past worn gaskets
or valves much faster than conventional oil, which is why I didn't
change to synthetic on my 150k 525i. In my experience, synthetic flows
quite rapidly especially in cold weather.

- Scott

> Since I filled my 1991, 750iL with Mobil 1, 0W-40, the low oil level
> alarm has started going off when the (overnight) dipstick level is 1/4
[quoted text clipped - 12 lines]
>
> Jan Fure

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Malt_Hound - 24 Jul 2005 14:38 GMT

> I have never heard that synthetic "clings to surfaces" and takes longer
> to drain but I do know that synthetic oil will sneak past worn gaskets
[quoted text clipped - 3 lines]
>
> - Scott

This is an urban legend, IMO. A synthetic maintains viscosity closer to
its rated value(s) over the lifetime of the oil. There is no reason to
believe it will leak past gaskets more than a thinned out dino juice.

The only *possible* reason for this oft quoted legend would be that the
superior cleaning properties of the synthetic may actually disolve some
of the gook that has built up inside a higher mileage engine previously
subjected to only cheap oil. That gook could be sealing your dried out
and leaky gaskets, but I have never experienced this phenomenon and I've
switched several high mileage cars (over 100k miles) over to full
synthetic with no leaks or increased consumption.

-Fred W

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Huw - 13 Jul 2005 21:38 GMT

> Since I filled my 1991, 750iL with Mobil 1, 0W-40, the low oil level
> alarm has started going off when the (overnight) dipstick level is 1/4
[quoted text clipped - 10 lines]
> conventional oil, or would the risk of overpressure exist during
> startup?

I think you read too much science fiction.

Huw

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