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Old 28th October 2016, 19:38   #11
SD1too
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Quote:
Originally Posted by COLVERT View Post
On the oil containers here in France I have seen the words --Low Ash-- on the labels of some of them.
Thanks John. I've not seen that in the UK though, so I'm hoping that Tiff will explain.
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Originally Posted by BigRuss View Post
Low ash oils are essential if you've got a car with a Particulate filter (DPF)
Why is that Russ?

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Old 28th October 2016, 20:47   #12
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Remember when everyone used CASTROL GTX no matter what car...?
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Old 28th October 2016, 20:56   #13
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Remember when everyone used CASTROL GTX no matter what car...?
I finally opted for a Castrol 5w30, it was cheaper than the halfords Peugeot special.

Car is a 2005 1.6 hdi but only 30k on the clock. Purchased from Jersey with 10k 8 years ago, it now pootles around the Isle of Wight. My wife did go nearly 40 mph the other day! It often just sits on the drive for days on end. I change the oil every 8-10 k, and it is running well. Hopefully it will continue to do so.

She loves it and it keeps her away from my CDT!

Thanks for all the comments.

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Old 28th October 2016, 21:18   #14
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Quote:
Originally Posted by Tiff View Post
If it's a 1.6 hdi, be very careful which oil you use,it has to be low ash oil as these have a real issue with carbon build up and eventually turbo failure. Volvo use this engine too but specify their own grade and haven't seen this issue on those yet.
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Originally Posted by SD1too View Post
Tiff; how does the consumer establish from the carton whether a particular engine oil is "low ash"?
Several oils are marketed as low ash or low saps. If it isn't - well then it isn't.
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Low ash oils are essential if you've got a car with a Particulate filter (DPF)
As our cars don't have one there's no need to worry if it's low ash or not.
As above - my Megane (M9R engine) low ash oil for it's DPF. I got 10l of fully synth from eurocarparts (Triple WX) for £39 which isn't too bad.
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Old 28th October 2016, 22:00   #15
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Why is that Russ?

Simon
Sulphated ash is a by product of diesel combustion, by using a low ash oil it helps reduce the amount produced that could otherwise block the DPF

There's different Saps ratings of oil (Sulphated Ash. Phosphorous. Sulphur ) the lower the better for a DPF.

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Old 28th October 2016, 23:08   #16
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Sulphated ash is a by product of diesel combustion, by using a low ash oil it helps reduce the amount produced that could otherwise block the DPF ..
Thanks Russ, but I am struggling to understand how engine oil can have an effect upon diesel combustion. After all, the two should never come into contact.

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Old 28th October 2016, 23:27   #17
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It only takes a few parts per million of engine oil usually from between liner and piston, valve stems or from the breather system to dramatilcally increase the amount of ash produced during combustion.

By using a low SAPS oil it's developed to reduce this but it can't get rid of it totally.

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Old 28th October 2016, 23:30   #18
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Extract from Machinery Lubrication publication:
Quote:
Sulfated Ash
The term sulfated ash relates to the amount of metallic elements in engine oils, which are mostly derived from the engine oil's detergent and antiwear additive chemistry. These additive packages contain multiple components based on metals such as calcium, magnesium, zinc, etc. Because a 100 percent seal between the piston rings can never be achieved, a certain amount of engine oil will enter the combustion burn.

As the engine oil enters the combustion chamber and burns, its residue forms an ash-like material. This ash-like material contributes to deposits in the crown land above the piston ring as well as to deposits in the ring grooves. These deposits can lead to rubbing wear on the cylinder liner and cause the piston rings to not operate freely. Ultimately, as the cylinder liner-to-ring interface is compromised high oil consumption can occur. In addition to these deposits, inorganic compounds from the lubricating oil's additives can become oxidized during combustion and generate metal oxide particles. These particles can be carried downstream with the exhaust and collect on the diesel particulate filter. These ash particles cannot be removed by filter regeneration because they are not combustible. As the ash particles accumulate, they result in filter blockage that increases back pressure to the engine, increasing fuel consumption and decreasing power. Ash particle buildup also necessitates more frequent cleaning of the particulate filters by mechanical means such as compressed air or water-pulse methods.
An engine oil's sulfated ash content also directly relates to an engine oil's acid neutralization capabilities (BN), because most of an engine oil's BN comes from the metal-containing detergent additives. Generally, the higher an engine oil's BN, the higher its ash content and the greater its ability to prevent acidic corrosion in the engine. Fortunately, with the mandated use of ultra low sulfur diesel fuel in on-highway applications, corrosion from fuel sulfur will require less of a need for BN control and thus a lower ash content.

In the analysis of oils, fats and waxes, the 'ash' value is obtained by combusting a weighed sample in a furnace at around 800C. The resulting solid (the ash) is sometimes treated with sulphuric acid and recombusted to convert the metal oxides (the ash) into sulphates, hence sulphated ash. Either way, the result is expressed as a percent by weight.

Last edited by T-Cut; 28th October 2016 at 23:36..
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Old 29th October 2016, 07:55   #19
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It only takes a few parts per million of engine oil usually from between liner and piston, valve stems or from the breather system to dramatilcally increase the amount of ash produced during combustion.
Thanks Russ, but that increase surely cannot be significant otherwise every engine in the world, diesel and petrol alike, would suffer, according to the explanation posted by T-Cut, from cylinder bore wear and high oil consumption.

Presumeably we are expected to assume that engine oil marketed specifically for diesels is "low ash", but I have not seen this specifically quoted by the manufacturer on packaging. That begs the question: what about oil marketed for petrol engines, what is its ash content? That's never declared either as far as I can see. All we get from the industry is the sort of wooly nonsense published by the ACEA!

So, I keenly await a post from anyone who can find oil packaging which declares scientifically its ash content.

Thanks for your useful replies Russ and T-Cut.

Simon
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Old 29th October 2016, 08:11   #20
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Struggling to follow all the technical stuff, but back to the original issue , why is 5w30 for a ford diesel £11 cheaper than same grade for a Peugeot? All the same ash issues, oil passing the piston rings, etc. must apply to both makes of engines. Sounds like a scam to rip off some customers!

The Castrol fully synthetic I have used seems to claim to be good for all diesels, if different makes of engine need slightly different oil, why don't Castrol supply different oils as Halfords do? Took the 307 out for a blast around the Isle of Wight after the oil change. Did over 40 mph down the military road! Ran very sweetly, no smoke as I raced through the gears.

The 307 is no CDT though!
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