This is a pretty interesting subject since oil has changed so much from when most all 2 cycle oil was intended for outboards since that was the biggest market. I found this discussion on another board and thought it would be appropriate. Sorry for the long post but there's a lot of new information when it comes to oils and the oils themselves are evolving (witness the new Mercury Rejuvenate that just came out).

The older oils had American Petroleum Institute (API) rating of "TC". The Boating Industry Association (BIA) rating of "TC-W", or the National Marine Manufacturers Association (NMMA) rating of "TC-W II." and these oils were originally developed for outboard engines, however, motorcyclists that used these oils found that their air cooled engines ran the best on the oldest API TC oils. These API TC formulas contained a higher level of bright stock 150, a high density petroleum base stock with a consistency similar to honey, that gave the best protection against piston seizure and bearing failure. To prevent carbon buildup in the piston ring grooves, these TC oils used metal based detergents that were very effective in air cooled motorcycle engines but caused problems in outboard engines when operated at long periods of time at one throttle setting. A whisker-like bridge could form across the sparkplug gap to permanently foul a cylinder under these conditions while the motorcyclist operating his engine at a constantly changing throttle setting never encountered this problem.

When the BIA developed the TC-W rating, they excluded the use of these metal-based detergents in favor of organic detergents to eliminate this problem in outboard engines. These TC-W oils (two-cycle, water cooled) also contained lighter base oils without the bright stock 150. The thought being that since outboards ran cooler they didn't need the thicker base stock. For engines operating in the 4,000 rpm to 5,000 rpm range, the absence of the bright stock 150 had no affect on piston and bearing life. However, off-road motorcyclists testing these new TC-W oils were disappointed with the bearing life of their engines operating at 10,000 - 11,000 rpm and quickly returned to using the TC oils.

The need for a clean two-stroke outboard oil was recognized when piston ring groove carbonization was seen as a primary cause for engine failure and a new formula designated TC-W II was developed. While this oil was significantly better for outboard use and was phosphate free, it still was not the optimum two-stroke oil for engines operating above 8,000 rpm. The phosphate free mandate was from a concern raised by environmentalists that realized that outboard engine use could permanently pollute fresh waterways. Recently, efforts to develop an even cleaner outboard oil have produced the latest NMMA TC-W3 and this oil, although containing no bright stock 150, has produced better levels of lubricity and cleanliness in piston ring groove areas, however, it is still not nearly as good as an oil for high rpm applications.

The BIA evolved into the National Marine Manufacturers Association (NMMA) which works closely with the outboard manufacturers. the NMMA mandated that all oils would contain non-metallic detergent additives, no phosphorus or phosphates, if they were to have the approval of the NMMA and the outboard engine manufacturers agreed to recommend only the NMMA approved oils. This is a big problem for higher revving engines. Ring sticking, port depoists and low temperature oil flow have been problems with TC-W3 oils.

Also, many marine dealers were concerned about the flammability and flash point of out board oils. Since larger engines were now consuming huge amounts of oil they had to stock several hundred cases of oil per season. This amount of oil stored in one location had alerted the fire marshals and insurance companies attention and a solution to this risk was addressed by the NMMA. Higher flash point oil with a flash point over 200 deg. F was what they needed to achieve a category 3B fluid rating, just enough to avoid the hazardous storage and shipping restrictions they were facing with all other two cycle oils. Oil manufacturers were forced to use TC-W3 additives or blends with high flash solvents if they were allowed to keep the NMMA license. The high flash solvents caused all sorts of unburned oil problems in engines.The combination of non-metallic/non-phosphate detergents and high flash solvents in the new TC-W 3 oils later caused some severe ring sticking in many engines and Yamaha actually required owners to use a 'ring-free' fuel additive to maintain their warranty, a symptom of being forced by the NMMA to recommend the new oils.

In Japan, engine manufacturers have developed a series of strenuous engine tests that can identify poor quality oils if they don’t measure up in performance. This became the JASO classification system. (Japanese automobile standards organization).

The tests include a detergency test, lubricity test, initial torque test, exhaust smoke test and exhaust blocking test.

JASO FA - Original spec established regulating lubricity, detergency, initial torque, exhaust smoke and exhaust system blocking.
JASO FB - Increased lubricity, detergency, exhaust smoke and exhaust system blocking requirements over FA.
JASO FC - Lubricity and initial torque requirements same as FB, however far higher detergency, exhaust smoke and exhaust system blocking requirements over FB.
JASO FD - Same as FC with far higher detergency requirement

In Europe, European two-cycle engine manufacturers were simultaneously working on two-cycle oil tests. They found that European two-stroke high performance engines needed an oil with a better detergency and higher temperature performance than the best JASO "FC" oils. In April, 1997, they published their ISO global standards for two-stroke oils with two quality level categories: ISO-L-EGB and ISO-L-EGC. The ISO-L-EGB aligns closely with JASO "FB" and the ISO-L-EGC aligns closely with JASO "FC". Then, they developed the "GD" detergency test to run hotter and longer (3 hours vs. 1 hour) than the JASO test. It didn’t take long for oil manufacturers to develop oil formulations that pass this new quality test, and most of them involve using synthetic base oils.

The problem with some synthetic basestocks (ester especially, which Amsoil, Klotz, and Redline use), is that they are hygroscopic (they absorb water)...which creates corrosion issues. Some combat this with additional additives, with varying success. Rust films on iron liners and crank wheels during a 2 week storage period have been common unless engines were fogged after shutdown.

Oils like Klotz R-50, Amsoil Dominator, and Redline Racing should only be used in racing situations (long WOT runs and frequent engine tear downs). Redline and Klotz specifically state this in their product descriptions. Racing oils have very high flash points and more anti-wear additives, so they can cause deposit and sludge issues, more smoke, and more pollutants released into the water. The harder you run them the less deposits they build up, but they are by no means clean burning. I'd also highly recommend fogging with a conventional oil after each use to address the corrosion issue.

Bottom line is that a JASO FD oil is really good stuff. It has a lot better lubricity and keeps the engine a lot cleaner than TC-W3 oils. It's a lot better at high RPM (something we need badly). You shouldn't need to use a high oil ratio with these oils, but if you do use more oil they aren't going to carbon up nearly as much as the older oils or a TC-W3 oil. FD rated oils are recommended for high rpm air cooled engines, but don't build up deposits like the old TC oils in cooler running outboards. You should at the very least be looking at an FC rated oil for any serious high rpm application.

The Quicksilver Rejuvenate is an JASO FD rated oil that was developed for the Mercury heavy fuel Optimax, that was burning jet fuel and needed better lubricity and better detergent additives than conventional oils. The heavy fuel didn't evaporate as much during injection and a lot more fuel was getting on the cylinder walls. This caused piston and ring problems so an oil with better lubricity was required to fix the issues, so this oil has really good lubricity. Much better stuff than any TC-W3 oil.

I'm also looking at the Schaffer racing oil, here is a link. This stuff is an FD oil and also has a moly additive that I like and also says that it has good corrosion protection, so I plan on trying it next season...

http://www.schaefferoil.com/cmss_fil...006%20Logo.pdf

Not sure what oil ratio I should be running with these oils on a older engine at high rpm, but I will run a lot of oil and keep an eye on the deposits.