clean oil

johns

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does anyone know to get your clean oil to stay clean (for a while anyway)i have changed the oil and even used an engine flush about 4 times but as soon as i check the oil it is instantly black i have ran the engine for about 10 minutes between flushes
 

pvb

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It\'s meant to be black...

Oil helps to remove the impurities in your engine, and will hold the smallest ones in suspension. So it goes black. Who cares? Change it at the recommended intervals, and forget about it the rest of the time.
 

jfkal

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Re: It\'s meant to be black...

Yes and no. It will turn black certainly over time. However going black immediately might indicate substantial blowby where combustion gases would contaminate the oil very rapidly.
 

aztec

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keep changing it. i change the engine oil (but not always the filter) every 3000 miles, sierra 1800 cvh. now done 160,000 miles on origional engine, and uses no oil, and engine never been apart. iv'e looked after the car since 16,000 miles, and the oil is always clean.

same with the boat, change the oil.. cos it's easy, and if i had to take it apart on board, i don't have to worry too much about the oily mess.

good luck, steve.
 

charles_reed

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I am assuming yours is a marine diesel engine.
The problem of most marine installations is that you have to extract the oil through the dipstick hole.
It is very seldom that you can remove all the old oil, so any new oil put in quite quickly discolours.
Even using flushing oil is unlikely to totally remove combustion deposits and it needs very little of those to discolour diesel engine oil, which in any case has high detergent qualities and quickly picks up any impurities.
Even when used in a non-combustion situation (such as a prop-bearing) it changes colour as soon as it has been in contact with the bearing.
 

seaesta

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Steve

You are very right. i used to run a fleet of 50 ton dump trucks in an opencast mine. Some of the fleet were Cat 773s which were famous for having crap engines. I introduced engine oil changes at twice the recommended frequency and the engines were more reliable and long lasting than the supposedly superior 773b's on standard oil change frequency.
I changed the oil at double frequency on my diesel 405 and it went 154,ooo with no problem or serious sign of wear. It is certainly a mistake to believe in 12,000 mile oil changes. I am now an oil change nut
The boat engine oil gets changes every verse end and so far it is running O.K (1965 engine)
Martin
 

celtic

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my "engine guy" pulls out his hair when people mention flushing oil--he says that in using flushing oil the problem is that it dilutes the new oil put in. Oil change as often as you wish but don't use flushing oil
 

vyv_cox

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Very true

Modern ashless dispersant oils have a better flushing effect than any flushing oil, which is usually only the base oil with no additives. Flushing oils are an outdated concept totally unnecessary if good quality detergent oils are used.
 

dickh

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I agree with regular oil changes as per manufacturers guidelines - one of my Citroen BX diesel did 194,000 miles before it was part exchanged, and the engine was still running well. The oil and filter was always changed at the correct mileage - 6000 miles if I remember. My current car, Peugeot HDi diesel has 12000 mile oil changes with Semi Synthetic oil and I will stick with this. Car manufacturers test oils for this sort of mileage and I'm sure they are being conservative.
No experience of Cat engines so cannot comment on your oil changes, but certainly increased oil change frequency will do no harm at all.

dickh
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VMALLOWS

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Re: Very true

My BUKH specifies a straight SAE 20 or 30 CC/CD oil. This is totaly unknown at mass market outlets (Halfords, WallMart, etc) and exhorbitantly priced at BUKH dealers (c. £20/5l). In my (old, diesel) car I of course use 15/40 CE at about £5.99

Fortunately, my local indepenent spares shop can get straight 30 CC to order at £9.99.

I know there are some very knowledgable chemist types out there. Is my hypotheses that using a multigrade (ie 15/40) would be damaging in the Bukh correct........because it would never heat up sufficiently and would always be too thin.? I also believe I may have destroyed a Briggs/Stratton lawnmower engine
because the multigrade oil was too THICK when hot (valve stems siezed).
 

PeterGibbs

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Re: more important than discoloured oil

From a number of years' experience of a Bukh 20 I can say that regular marine diesel multigrade mineral oil is fine. It will discolour quickly as particles are absorbed into it - not to worry. If filters are changed as required - each season or 100 hours whichever is sooner- all should be well.

With this engine the greater concern is black butter, not discolouration. This occurs when water passes the circlip on the water pump housing and infiltrates the engine proper. This can happen faster than you imagine. Then black butter - oil and water mixture - will accumulate under the rocker cover. Shortly the springs will rust and you are into significant expense. SO check under the rocker cover routinely; just about every Bukh owner will experience this event sooner or later. No worry, just purge the butter from all parts of the engine. Change the oil entirely, and filters, immediately, and all should be well.

Peter Gibbs.
 

VMALLOWS

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Re: more important than discoloured oil

Peter,

Pleased to hear you've had no problems with multigrade oil.

Not sure if you really mean water pump 'circlip'. The two seals certainly do wear out, though in my experience the outer (water side) one goes first and then you can spot the drips from the drain hole (assuming its not blocked) before any water finds its way into the engine. The seals are standard and much cheaper from an industrial seals/bearings supplier. The biggest problem is that many people fit them the wrong way around! (my originals were!). (the 'hollow' part of the seal must face the side FROM which the fluid would leak....thus on the water pump both 'flat' sides face towards the centre of pump.
 

david_bagshaw

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How regularly has the oil been changed in the past ?

Sounds as if there could be a lot of "solid dirt" stuck to the sides, which is now being washed off.

David
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seaesta

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Dickh

There are a few reasons for changing oil. One is the chemical changes as the oil neutralisies acid which arises from burning the sulphur found in most marine diesel. This neutralisiation produces sulphated ash which is not good to have around. In practice the oil will have suffieicent TBN (neutralising capacity) to cope between regular oil changes.
However I have seen graphs produced by Shell showing deterioration of performance of engine oil in preventing wear as the oil is used. Performance is better with new oil.
For me the main issue is particulates - especially abrasive ones. The oil "filters" we use have a nominal rating on 60 micron (thats the size of bits of crap that get through) and must of the abrasive wear is a result of particles smaller than 60 micron grinding away in the engine as it works. So these small abrasive bits go round and round the engine and the more often you remove them (by changing the oil) the less wear they cause.

Martin
 

PeterGibbs

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Re: more important than discoloured oil

Replying to your query. On the shaft that drive the water impeller there is a circlip, about midway in, positioned between the two rubber seals, which are to be installed as you say. The clip should also be sited in line with the holes through which water will be ejected if it passes the first, outer, rubber seal. As you say, these holes are designed for this purpose and some drips are normal. The clip should spin off these drips and prevent water moving further towards the engine, so passing the inner seal and fouling the oil in the engine.

When drips through the holes become noticeable, have a look at the clip; if it is rusted this is a sign of significant water passing the outer rubber seal. I found the clip needed replacing every second season, and I replaced the two seals at the same time. As you know, it is not a big job on the Bukh to maintain the water pump - just vital that it is on the regular check list. Having had black butter twice through not watching as closely as required, and then having to purge the engine of all oil and butter etc, it is worth the effort to stay on top of the water pump.

That said, I recall there is little else with this engine that requires such close attention - perhaps the exhaust elbow comes next. It will crack with time owing to the passage of hot gasses and exhaust water. Do have a spare to hand to replace when this happens; providing the 4 retaining nuts are serviceable it is easily done in an afternoon. Binding a leaking elbow up will only work for a short while, and pouring water into the engine compartment is not a viable alternative to action!

Good luck,

Peter Gibbs
 
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