I've gone back and copied some of the information on the change in engine oil specifications which went into effect in 2007.....
the newest gasoline engine oil service classification is api: “sm.” one of the primary reasons why the epa wanted to introduce this requirement was the concern that for engines which burned a little oil, the zddp (zincdialkylditiophosphate), was poisoning catalytic converters. The major automotive manufacturers at first stated that there was no bona fide data to confirm this theory, and even today, it is still debatable. The government calls for catalytic converters to have a minimum useful life of 120,000 miles, most catalytic converters have far surpassed that mileage in use without having an abnormal amount of failures due to the so-called “poisoning.” zddp is the major anti-wear additive in engine oil, it has been used for decades, it is relatively inexpensive, yet very effective. With the lowering of zddp in some oils, almost nothing in some other oils due to “additive drop-out conditions” (primarily in semi-synthetic and some synthetic oils), a devastating effect has occurred. The first casualties of low-to-no zddp took place in high-performance gasoline and methanol fueled engines. One case which I know of “flattened” three camshafts within a two-month period in a race car situation. Excessive valve train wear has also been experienced with this oil.
Independent engine builders recognized the problem almost immediately and started recommending to the industries they serve to use a “high-quality” oil with zinc in it for anti-wear protection. Most all of the majors, including those who produce private label engine oil for companies, such as for auto parts stores have changed their formulations to meet sm. You will see it on the shelves at the stores, and from the oil jobbers.
Diesel service rating “cj-4”
the newest diesel engine oil service classification is api: “cj-4,” sometimes just referred to as “cj.” the major cause of change for this rating was to meet the 2007 low-emission diesel engines specifications. The concern once again was due to exhaust emissions. It had been determined that on engines using a dpf (diesel particulate filter), it would be plugged up by the heavy metals in the additive package of the engine oils which were graded up to ci-4 plus. The newer diesel emissions systems can reach temperatures as high as 1,600º f. Heavy metal additives destroy the system. Therefore any engine oil prior to cj-4 which is not formulated for these engines should not be used. According to the new specs for cj-4, the oil must contain lower levels of zddp, calcium and phosphorous, it must also not have a tbn any higher than 9. Tbn is a measure of the oil’s alkaline reserve, which is used for fighting off the damaging effects of acid. Diesel oils which are formulated for “low-emission engines” when used in pre-2007 engines has been reported as having premature bearing wear in as little as 10,000 miles. Furthermore, if any type of oil additive is used to help the friction modification of these oils, including molybdenum disulfide , they will also poison the system in diesel applications.
I cannot tell you that it would be ok to run the 306sl engine oil in an engine which requires sm, however I can tell you that I have several customers who do so and in doing so are not taking warranty requirements into consideration. They prefer the 306 because of the higher additive levels than even the 303 has, and have the mindset that it would be cheaper to replace a catalytic converter than to replace an engine. Not to say that either one would occur. Having an engine which burns oil is just one reason for a catalytic converter to fail, and there are literally millions of cats out there in which the engine was using pre-sm oil with an excess of 120,000 miles on them (which is one of the epa's main concerns).
So, with that in mind, the choice is up to you......
Dick
