300D oil concerns

Couple things about oil in my recently acquired '83 300D: Seems to get black pretty quick (1K miles?), and my pressure is a little erratic--good at relatively high engine speeds, down
around '1' at idle (1 what, by the way?). Lately it seems even lower at slow speeds, but the oil level seems okay. Do oil pumps give out? Could the sensor/gauge be unreliable?
Thanks in advance,
Barye Phillips
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300D oil concerns
NORMAL 1bar=14psi <i think> jittery pointer a idle is the norm also as long as it goes to 3 when your rolling your fine. change every 3,000 miles and you will be ok. keep an INLINE fuel filter in your glove box. TRUST ME ON THIS ONE!
case
Group: alt.auto.mercedes Date: Tue, Nov 4, 2003, 2:14am (EST+5) From: snipped-for-privacy@worldnet.att.net (BaryePhillips) Couple things about oil in my recently acquired '83 300D: Seems to get black pretty quick (1K miles?), and my pressure is a little erratic--good at relatively high engine speeds, down around '1' at idle (1 what, by the way?). Lately it seems even lower at slow speeds, but the oil level seems okay. Do oil pumps give out? Could the sensor/gauge be unreliable? Thanks in advance, Barye Phillips
the case, minus a few cans!
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Diesels' lube oil is black about 10 minutes after it's changed - Normal.
As to the engine's oil pressure, the gauge will "peg" when the engine's speed is over say, 1,200 rpm and fall to 1 BAR to 1.75 BAR at idle. Use SAE 10 - 30, 20-40 or 20-50 weight. Don't use 0 or 5 weight oil - too light.
Inside the oil filter canister are two rubber "O" rings which harden and should be replaced - but shops "forget" this task. Hardened "O" rings allow some oil to leak past the filter; this causes the oil pressure gauge to vibrate.
There is no sensor, the gauge is an oil pressure gauge and will drip oil onto your shoe if it ever leaks!
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The reason your oil turns black right away is because when you change the oil not all of it gets drained-- there is still old oil left in the oil cooler that turns the new oil black right away. The best oil to use is CD-4, easily found in 15w-40 weight. This oil is specifically formulated for 4-stroke diesels and is what the truck diesels use. You oil gauge reading sound normal.
--Geoff
Barye Phillips wrote:

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it is possible that some old oil remains after a change, but this is not the primary reason that diesel lube oil turns black: that is because it becomes quickly contaminated with particulate by-product of combustion.

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Yes, that is why the oil eventually turns black, but what I think we are talking about is why it turns black immediately after changing it. Trapped or residual oil that is already black mixing with the new oil turns it dark immediately.
--Geoff
atwifa wrote:

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Well, suppose one would change the oil on it's Diesel weekly, you'de think eventually it stays clear looking like in the bottle, no still not, it's the combustion by product which is good and bad. Bad it turns the oil black, good because obviously and I should know, diesel engine don't have nearly as much internal carbon built up than a compatible gas engine. Obvious unburned diesel in the oil keeps carbon from building up. Cheers. Autobahn Auto
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