Can I have too much or too little ash in my oil?

Nov 16, 2002
Sounds like they're still moving toward even lower SA levels.

From SonofJoe:
"A number of Europe's so-called 'high ash' oils started out as being formulated as 'medium ash' oils but were deliberately forced into the high ash camp by ACEA in 2010.

Prior to 2010, you might typically throw together an SL/CF/A3/B3/MB228.1/VW505 oil with 1000 ppm of Phos (so about 1% ZDDP) & 8 TBN (eg 2% 400 TBN Mg Sulphonate). The sulphated ash level might be just shy of 0.8%. There were no formal specific limits on Phos or TBN but there was always massive commercial pressure to minimise DI treat rates & this typically was how things fell out. Yes, the specs said in theory you could go up to 1.6% sulphated ash but nobody in their right mind ever went that far because the law of diminishing returns comes into play.

In 2010, ACEA in its infinite wisdom (sarcasm alert!!) decided that some clear blue water needed to be put between normal oils & the newly emerging low SAPS oils. This they did by slapping a 10 min TBN spec on the older oils. This was easy to implement. You just threw in an extra 2 TBNs worth of over based detergent (in practice a bit more because commercial blenders need a safety margin above the minimum). It was an act of pure spite, a deliberate & unnecessarily costly poisoning of the well to 'encourage' the shift to Low SAPS oils.

Such is life I suppose.."

"A lot of folks misunderstand the logic for putting over-based metallic detergents in oil (the stuff that largely gives an oil its TBN & the bulk of its Ash). It has almost nothing to do with 'cleaning' or high sulphur fuels. The first 5 TBN is usually there for rust prevention as defined by the Ball Rust Test. This might get raised to about 8 TBN to neutralise the complex carboxylic acids that form when base oils oxidise as they get exposed to hot, reactive blow-by gas. Typically 8 TBN is way too much for oil in normal service but it would definitely all get used up in the severe industry oxidation tests like the Sequence IIIG.

There's no harm in buying oils with 10+ TBN but TBH, there's not a lot of benefit to be gained either. The fact is that modern base oils (Groups II/III/IV/V) are massively more resistant to oxidation than old fashioned Group Is. If they're not breaking down, then there's nothing for the detergent to neutralise, so any excess just sits in the oil, doing naff all, until it's time to throw the oil away."

"Unfortunately it isn’t a straightforward answer, because the “ideal” level of ash is also going to be dependent on valve geometry and materials. But yes, in the ballpark of 0.5% is where the industry is moving."

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Blow by is acidic. I could be wrong cause I am forgetting most every other thing, but call it a guess and if I am correct call me Mr. wonderful and if I am wrong ,, say there is no fool like an old fool. Nitric acid . Low ash will probably be for the high exhaust soot DI engines particulate filters. Some will say the ash helps lube the valve seats .
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If I'm not mistaken, SonofJoe was in favor of the higher SA oils over the mid/low SAP oils we see today.
If I'm not mistaken, SonofJoe was in favor of the higher SA oils over the mid/low SAP oils we see today.
I hope I don’t cause any issues by asking this question, but what happened to SonofJoe? His posts are very insightful.
"One other thing... Most folks would consider an engine oil to be shot when the TBN reaches 2 - 3. This isn't actually the case. An oil can function quite happily with a TBN of zero. The thing you have to remember is that oil formulators don't tend to focus directly on stuff like TBN depletion, acid formation or oil oxidation. What they're really concerned with is the onset of exponential viscosity increase. For many of the lengthy, industry standard engine based oxidation tests, it's both impractical and uneconomic to just use over based detergent to control oxidation. Given how fast it can deplete, you might need an oil with a starting TBN of around 20 to keep the TBN above 2 at the end of the test! For this reason, modern oils contain a cocktail of various Antioxidant chemistries, each of which plays a role in keeping the oil from 'breaking' long after the TBN reserve has been exhausted. Just to be clear, there's nothing wrong per se with changing out your oil when the TBN hits 2 - 3 but if you do a UOA, and find the oil's TBN is zero, it's not something to freak out about."