What qualities are most important for extended drain?

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33,975
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Southern NJ
I'm not clear on what exactly makes an oil a good "extended" drain oil? TBN plays a big part but what do specs. such as HT/HS and DB 229.3 have to do with it? If you take Amsoil, M1 and Schaeffers, all can go many miles but what makes one more suitable for extended drains then another? I believe all of Amsoil's oils pass the DB 229.3 test, while only 0w-40 M1 does in the Mobil line.
 

Patman

Staff member
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21,989
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Oakville, Ontario
I don't think you can see in most technical specs as to the qualities needed to make a good long drain oil, other than TBN, but even then it's misleading, since Schaeffer Oil has lower TBN than most extended drain oils, but yet it shows to retain it's TBN well. The only real way to see which oils are suitable for extended drains are to run them in your engine and do UOAs. Then you see which oils hold their viscosity well, hold their TBN well, and those which don't oxidize too quickly also. It helps to have the guidance of someone like Terry Dyson too, he can read oil analysis reports better than anyone, and can offer up the best advice as to the right interval with your engine/oil combo.
 
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5,785
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Dixie
buster, I'd say a high resistance to degradation from oxidation and nitration, which leads to oil thickening and depletion of the detergent/dispersant additives. This causes the TBN to drop and eventually limits the service life of the oil. I also like to see decent shear stability, although with a long drain interval you can count on the oil to slowly thicken after any initial shearing occurs. Along with this you need a robust amount of antiwear additives, which also act to limit oxidation and oil thickening. You also want an oil that is resistant to fuel dilution, although I'm not sure what attributes help in this respect. The best way to start this process is with a high quality, blended PAO and/or Ester basestock. These seem to have the best overall range of desirable properties, including resistance to moisture, additive solubility, seal compatibility and extreme temp properties. There are a number of approaches that work with regards to additive chemistry. If you look at Amsoil, Redline and Mobil 1/Delvac 1, there is quite a variation in chemistry. Yet all these oils seem to consistently hold up very well. The variables that cause oil to degrade are heat, oxidation, blowby chemicals and moisture. In diesel engines the buildup of soot is also a major factor ....From the standpoint of chemical engineering, it's a hard problem to solve. TooSlick Dixie Synthetics
 
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418
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OR
"Ester basestock is resistant to moisture"??? I thought Ester basestock had high hyrgroscopic properties. (ie moisture absorption)
quote:
Originally posted by TooSlick: buster, I'd say a high resistance to degradation from oxidation and nitration, which leads to oil thickening and depletion of the detergent/dispersant additives. This causes the TBN to drop and eventually limits the service life of the oil. I also like to see decent shear stability, although with a long drain interval you can count on the oil to slowly thicken after any initial shearing occurs. Along with this you need a robust amount of antiwear additives, which also act to limit oxidation and oil thickening. You also want an oil that is resistant to fuel dilution, although I'm not sure what attributes help in this respect. The best way to start this process is with a high quality, blended PAO and/or Ester basestock. These seem to have the best overall range of desirable properties, including resistance to moisture, additive solubility, seal compatibility and extreme temp properties. There are a number of approaches that work with regards to additive chemistry. If you look at Amsoil, Redline and Mobil 1/Delvac 1, there is quite a variation in chemistry. Yet all these oils seem to consistently hold up very well. The variables that cause oil to degrade are heat, oxidation, blowby chemicals and moisture. In diesel engines the buildup of soot is also a major factor ....From the standpoint of chemical engineering, it's a hard problem to solve. TooSlick Dixie Synthetics
 
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