again, all kinds of theories can be produced to explain this apparent
problem, but what is needed is actual measurement with a pressure gauge
under various conditions. quite possibly the oil pressure situation is ok,
or at least marginal. in any case, if it does turn out that there is a
significant problem, and assuming the present oil filter isn't defective,
the fix will be mechanical - not switching brands of oil, or changing to a
black oil filter.

if the tolerances were a bit loose, oil pressure marginal, i could imagine
a flickering oil light under maximum strain; and my fix would be to just
drive with a light enough foot to avoid the dreaded flickering light.

dlk

On Wed, 7 Jan 2004 23:41:47 -0800, Ben S <phlogiston@ISPWEST.COM> wrote:

>well recent events (see my "blown head gasket?" thread) and the "oil
>light discovery" thread have gotten me thinking about oil pressure.
>
>to recap what happened to me: i have put over 20k miles on my van in the
>last 4 months, and many of those miles involved strenuous hill climbing.
> recently, i moved up to south lake tahoe and decided to switch to a
>lower viscocity oil because of the colder weather.  i did the oil change
>down in davis where it's warm and was driving back up the mountain that
>night when my oil pressure light came on.  i stopped and ended up
>getting the van towed.  after i mistakenly diagnosed my problem and was
>corrected by you guys, i drained out the 10w-40 that i had just tried
>for the first time and replaced it with 20w-50, which is what i had
>always used in the past with no problems.  since that change, i have
>driven over a few passes with no issues; but yesterday on my way up to
>kirkwood, as i was climbing a particularly steep hill (meaning i was in
>3rd gear at about 4k rpm for several minutes), the oil pressure light
>came on again!  so i let off the gas and the light went off.  after a
>few seconds, i tried to speed up again, and again the light came on.  so
>i slowed way down and cruised up the rest of the hill really slowly in
>second gear and didn't see the light again.  now for the record, i have
>a fram gold oil filter in there right now, and i have heard all the
>stories about non-german filters causing problems.  however, just before
>my recent oil change, i made several trips over these exact same
>mountain passes, driving just as hard, with castrol 20w-50 oil, and
>never had a problem AND i was using a napa filter then, too.
>
>so although i know that i need to start using a real german filter (i
>just ordered a 4pack from cafe volks), i think there might be some sort
>of slowly deteriorating condition here--it seems like some subtle
>problem must be getting worse.  what causes the oil pressure to get low
>enough to trigger the light?  assuming that the oil was getting too hot
>and thin from all the climbing, why did the pressure go up so quickly
>when i let off the gas?  the oil certainly can't cool down that quickly,
>and i would expect that a decrease in engine speed would decrease the
>oil pressure.  and wouldn't my coolant temp gauge have registered some
>kind of increase if the oil was getting too hot to maintain pressure?
> but that temp guage was pegged right in the middle like it always is
>once the engine warms up.  i don't think this problem is caused by a low
>oil level--i've been keeping a close eye on that.  but could it be
>caused by a fault in the pick-up tube?  or a failing oil pump?  what can
>slowly degenerate and cause the oil pressure to drop under a hard load?
> has anyone else had problems running 10w-40 oil?  my manual says that
>is safe for up to something like 75 deg F ambient temp, and it sure was
>a lot colder than that when i had this problem.
>
>thanks in advance for any help...
>
>Ben.