litmus paper test - modern diesel oils

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Sun 24 Jun 2012 17:38
litmus paper test - modern diesel oils - oldroverboy
Apart from the obvious way od doing regular oil changes and trusting that the garage have used the correct oil, is there any simple litmus paper type test for checking for diesel contamination in engine oil?

Edited by OldRoverboy on 24/06/2012 at 17:38

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Sun 24 Jun 2012 17:39
litmus paper test - modern diesel oils - oldroverboy
Apart from the obvious way od doing regular oil changes and trusting that the garage have used the correct oil, is there any simple litmus paper type test for checking for diesel contamination in engine oil?

Thats meant to be "of doing regular oil changes" but won't let me edit!

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Sun 24 Jun 2012 18:07
litmus paper test - modern diesel oils - RT

Regularly send oil samples away for oil analysis - US petrolheads do this regularly and the market is big enough that it's cheap there - it's expensive here, about the same price as an oil change !

Fit an oil condition sensor delphi.com/shared/pdf/ppd/sensors/et_oilcond.pdf not cheap I imagine !

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Sun 24 Jun 2012 18:27
litmus paper test - modern diesel oils - unthrottled

...or simply do your own using a piece of unwaxed white card. Let a drop of oil from the end of the dipstick fall onto a piece of card. Keep the piece of card suspended by the edges so that the part with the oil spot does not touch a surface. Leave the card in a horizontal position for twenty minutes or so.

Healthy oil should appear be translucent when held up to the light.

If it is opaque-and has a jagged edge then the oil is severely oxidised. This could be due to excessive heat, or due to the presence if glycol (antifreeze) which oxidises oil very quickly and is far more deleterious to oil than water.

Fuel dilution is manifested by light coloured halos around the main oil spot.

For diesel engines, you are mainly concerned by the ability of the oil to hold soot in suspension. If you see clumps of soot particles forming, then the oil is saturated with soot.

Use a card with a drop of new engine oil for comparison.

I keep regular checks and date them to monitor the deteriation of the oil. The results are interesting. After a long motorway journey (>200 miles) the oil always shows additional oxidation and the fuel dilution decreases markedly. During winter, with a diet of short journeys, the fuel dilution increases significantly.

It's a very old field test that is starting to be revisited.

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Sun 24 Jun 2012 21:43
litmus paper test - modern diesel oils - gordonbennet

Thanks for that Unthrottled, very interesting, i shall have a little play around with card testing.

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Sun 24 Jun 2012 22:17
litmus paper test - modern diesel oils - unthrottled

I was quite surprised-and it made me realise how useful oil/water coolers actually are. They speed up the warming of oil as well as limiting high temperatures.

I don't have an oil cooler. Oil temperature lags behind coolant temperature and can take 20 minutes to reach operating temperature. From then on, oil temp is basically dependant on engine speed. So for journeys less than about 10 miles (most of mine) the oil never gets hot and any fuel present won't boil out .

But with short gearing, if I cruise at 80, the tach is almost at 4000RPM. 100 miles of this and the oil is probably well over 100C, and it is going to oxidise.

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Sun 24 Jun 2012 22:35
litmus paper test - modern diesel oils - gordonbennet

Unthrottled, any suggestions why 'black death' could be showing its ugly mug again.

I know that combustion blow by around internally fitted injectors with seal leaks can cause similar carbon (or rather soot) build up in Diesels, but i have seen petrol engines in recent years (MB V12's as it happens) bench stripped with valve gear sludge build up reminiscent of 80's Fords.

Is it a symptom of neglected servicing, poor oil or even good oil left in too long, overheating, or a combination of things?, your views would be appreciated.

Edited by gordonbennet on 24/06/2012 at 22:38

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Sun 24 Jun 2012 23:49
litmus paper test - modern diesel oils - nortones2

Re unthrottled high oil temps at 80. Why? At 80 the engine is at say 35 bhp output. Barely enough to keep it warm:) Unleess you drive a V8 barn-door Range Rover?

Edited by nortones2 on 24/06/2012 at 23:50

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Mon 25 Jun 2012 00:48
litmus paper test - modern diesel oils - unthrottled

@nortones

Short gearing and no oil cooler. The oil is mainly heated by the viscous shearing of the pistons moving up and down, only the ttop of the engine is cooled by water. So the heating of the oil is dependant on engine speed. Even though I'm using 35-40 hp, it's still 4000 RPM.

@Gordon

re: sludge-I don't know. Oxidised oil does get very viscous. As I understand it, only certain engines were affected, and no one found a convincing pattern to explain the behaviour.

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Mon 25 Jun 2012 07:55
litmus paper test - modern diesel oils - oldroverboy
Thank You, unthrottled, tried it yesterday afternoon, and according to your words oil seems to be ok.
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Mon 25 Jun 2012 18:46
litmus paper test - modern diesel oils - Duncan112

We used to do a range of tests on lub oil on board ship,http://www.marineinsight.com/tech/proceduresmaintenance/how-to-test-lube-oil-lubricating-oil-onboard-ship/ tests 2, 3 4 & 6 can be easily replicated in the home, the flowstick might need a bit of construction, I would suggest two parallel groves routed in plexiglass or similar with two equal larger reservoirs at one end put a measured volume of used oil in one reservoir and new oil in the other and tilt, watch the oil go down the groove, if one drop is say 30% slower then it's time for a change

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Mon 25 Jun 2012 21:58
litmus paper test - modern diesel oils - MikeTorque

A simply test is to put a drop of fresh oil and a drop of engine oil onto an odorless waterproof object, then place the object under slow running warm water and note the difference. The more broken down the oil the easier it will wash off the object. The fresh oil should last longest. Then examine the oil smear left for each sample, the newer oil should feel smoother and slightly thicker than the older oil.

Also if you have a sensitive enough nose you will be able to tell the difference in smell between the two by putting a drop of each oil onto an odorless object as the test material. The older oil will smell of a little diesel (if the oil contains any) whereas the newer oil won't. NB: Don't do this if you have any known lung or breathing condition as it may trigger a reaction.

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Mon 25 Jun 2012 22:13
litmus paper test - modern diesel oils - unthrottled

This tests surface tension. Another version uses an old jam jar filled with water and allow a drop of oil to fall onto the surface. It should form a distinct blob and not disperse. i didn't recommend this because even one drop of oil makes a surprising amount of mess and you can't use the jar for anything else!

With a little practice, over-aged oil is easily distinguishable from acceptable oil. The dipstick merely tells you that there is a brown substance in the sump.

If cranking speed becomes slow and the engine braking is very aggressive when cold, then, assuming the battery is OK, that is an indicator of oil that needs replacing NOW. Of course, this effect is very gradual so you tend not to notice it.

with regards to the crackle test for water-I don't find it very reliable. I press the dipstick against the hot exhaust manifold. Since the oil smokes, the temperature is above 180C, yet I often don't hear crackling-even when there is mayo on the top of the filler cap and I know there is water in the oil.

Edited by unthrottled on 25/06/2012 at 22:18

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