Here is the definition of Energy(Now Resource) Conserving Oils from the API:
Quote:
2.3.2.5.2 Resource Conserving in Conjunction with API Service Category SN
API Service SN engine oils designated as Resource Conserving are formulated to help improve fuel economy and protect vehicle emission system components in passenger cars, sport utility vehicles, vans, and light-duty trucks powered by gasoline engines. These oils have demonstrated a fuel economy improvement (FEI) in the Sequence VID test at the percentages listed in Table 1 when compared with a baseline oil (BL) used in the Sequence VID test. Additionally, these oils have demonstrated in the tests listed in Table 1 that they provide greater emission system and turbocharger protection and help protect engines when operating on ethanol-containing fuels up to E85.
Many previous S-categories made reference to “Energy Conserving,” but this reflected an emphasis on fuel-economy performance alone. Resource Conserving in conjunction with API SN focuses on fuel economy, emission system and turbocharger protection, and compatibility with ethanol-containing fuel up to E85.
Basically what that means is based on your grade of oil there must be a Fuel Economy Improvement over whatever the Baseline Oil was; the oil must retain 79% of its phosphorus level (typically derived from ZDDP); retain no water; and not produce more than 30mg of high temperature deposits. Any oil that does not meet these requirements can no longer be considered a "RESOURCE CONSERVING OIL". The replacement of ZDDP with other additives has more to do with the reduction in PPM of phosphorus required by emission system standards.
What does that mean from a additive package standpoint? Typically 10-14% of an additive package is ZDDP; it is reduced to 5% if they are using a low SAPS standard. If you are removing ZDDP that means both wear protection and anti-oxidant levels are effected because that is what ZDDP does.
Oil companies are now using things like molybdenum disulfide and borated sulfonates and other FM/EP/AW additives(notice the presence of sulfur in both of these) to pick up the slack from ZDDP and they do a pretty good job most of the time. Where we run into more trouble is in oil oxidization. So oil companies are figuring out other ways to deal with that too. Phosphorus retention is also a concern and so using additional additives to help the phosphorus from depleting is also becoming a common practice.
In general older oils which do not meet these new standards (and generally have higher levels of ZDDP) are still fine for MOST new engines - however there are many exceptions especially in performance vehicles. Motorcycle oils which have very high ZDDP will work however you may run into problems depending on what vehicle, gas/diesel, what kind of emission system you are running etc etc etc.
So yes you can use high ZDDP oils in gasoline engines like motorcycle oils or certain race oils and so called "performance" oils that all have higher levels of ZDDP. On the flip side the newer FM react differently with metal surfaces including clutch plates than ZDDP does, which is why sometimes you can have issues with wet clutches. Motorcycle oil additive packages also use different levels of dispersants, rust/corrosion inhibitors, and other additive ingredients than engine oils designed for gasoline engines. (That said I know several motorcycle drag racers that use various additive package supplements that include all kinds of friction modifiers with great success).
on a personal note, I think it is funny that ZDDP has become synonymous with things like better wear protection in oil the same way MOLY has done so with grease. There are lots of other options in the industry, these ones are used most generally because they are the most "cost effective" (AKA they make oil companies more money)
