High ash oils and deposits

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263
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DFW, TX
Does anybody have any test data on high ash oils and their correlation to engine deposits? I have seen a bunch of responses here that recommend a 15w40 HDMO for older engines which burn oil. Is this really a good recommendation?
 
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London, AR
Chris A, Good question. I have a 95 PSD with a Cat. Conv. and it definetly takes 15W40 CI/SL oil. So to me if an oil has both ratings I don't see a problem with using it in an auto engine. I personally have never seen this tested and in writing. I do read alot of people say not to do it because of the ash content, but no documented facts. An API rated CI/SL 15W40 should not be a problem. I have seen some 350 cu. in. GM engines that the lifters would go nuts on a cold morning using this weight oil. That is the only drawback I personally see. Also the Phor. content of the HD oils are being lowered which is another plus. JMO
 

MolaKule

Staff member
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Iowegia - USA
I have some test data which I will share. What's the alternative though? Using a 15W40 HD is simply a stopgap measure until the engine is rebuilt. You would certainly want to replace plugs and use an upper chamber cleaner until the rebuild can come about.
 
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308
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SF/Bay Area, CA
Historically, high ash has been a concern relative to combustion chamber deposits in heavy duty diesel engines. For years, the magic number was to have a 1.0% ash content. That has evolved over the relatively recent past where ash content was not as strong a driver as TBN due to extension in drain intervals. Thus, most heavy duty diesel engine oils are now typically 1.3% ash and the associated TBN is higher as well. I honestly would not worry about the ash level of the commercially available 15W-40 oils in your vehicle relative to whether or not you'll see increased deposits. For perspective though, the ACEA standards for light duty diesel engines, for instance, allow for between 1.3 and 1.8% ash (see table 2b). PS - If you're really into it, here's a paper you can order from the SAE. There are other SAE papers that are more specific to the comments above but I don't see them as available online. [ April 03, 2003, 05:10 PM: Message edited by: 68redlines73 ]
 

Chris A

Thread starter
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263
Location
DFW, TX
quote:
Originally posted by MolaKule: I have some test data which I will share. What's the alternative though? Using a 15W40 HD is simply a stopgap measure until the engine is rebuilt. You would certainly want to replace plugs and use an upper chamber cleaner until the rebuild can come about.
I think the alternative is a High Mileage oil. It is thick like the HDMOs and has good NOAK #'s. It's a little more expensive ($2 per qt), but worth the extra piece of mind for me.% As a side note, I found some specs on M1 which show that it has an ash% of 1.2%-1.3% depending on grade. Most HDMO that I've found are in the 1.3 - 1.5% range. I know that they meet SL specs, but that alone is not enough for me to use it in a PCMO application.
 
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