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Re: OK, but I have no clue about phosphorus Posted by sam96CS [Email] (#852) [Profile/Gallery] (more from sam96CS) on Thu, 26 Feb 2015 09:20:10 In Reply to: OK, but I have no clue about phosphorus, Noel, Thu, 26 Feb 2015 07:01:16 Members do not see ads below this line. - Help Keep This Site Online - Signup |
How much is needed varies because different engines stress oil in different ways. This is the reason why the safest approach is to comply with the oil specifications that applied when the engine was made.
Saab says your '96 9K needs SH oil (approx. 0.12% phosphorus). I don't know about your 9-3 engines. Saab recommends for the '03 9-5 API SJ oil (approx. 0.1% phosphorus) or the more demanding ACEA A3/B3 standard. Actually the '03 9-5 owners manual says "API SJ or higher". The manual mentions API SL which "fulfils even higher requirements" than SJ, but does not officially recommend it. SL has approx. 0.1% phosphorus.
An adequate amount of phosphorus isn't enough. The oil has to survive high temperature and shearing forces, and to date decent HTHS performance is positively correlated with viscosity. In the Mobil 1 Oil Product Guide linked by JerseySaab every Mobil 1 oils that meets the ACEA A3/B3 standard is a 10W-30 or higher.
Oils that meet ACEA A3/B3 standard generally have 3 things in common. They are fully synthetic, relatively high in viscosity and have about 0.1% phosphorus.
You're in compliance with Saab's requirements for your B234 and B235 engines with Mobil 1 10W040 HM, and that is the reason why you aren't having oil related problems. You're right that one doesn't have to be a chemist or engineer to get this right.
My point is that there are ways to assume unnecessary risks. Those who assume that newer API standards are backward compatible with obsolete API standards or that thin "energy conserving" oils give good enough protection are disregarding Saab's recommendations. Nothing wrong with taking a risk if desired, but this risk has very little upside relative to the potential downside.
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