Copied this from another forum
This is also a good read from Spectro oils.
Most of the OEM manufacturers oils are produced by specialty lubricant manufacturers, not the OEM and these formulas are tested and approved by the manufacturer for use in their sleds. The oils are blended according to a formula that has been developed for two-stroke snowmobile engines and this oil is usually given a rating from the American Petroleum Institute (API) of "TC", the Boating Industry Association (BIA) rating of "TC-W", or the National Marine Manufacturers Association (NMMA) rating of "TC-W II." All of these formulas were originally developed for outboard engines and were modified to suit the needs of snowmobile 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 motorcycle engines but caused some 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. 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 just as the soap industry was beginning to eliminate phosphates from their products for the same reasons. But, snowmobiles, motorcycles and quads do not emit their exhaust directly into the water, as outboards do. 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, still not nearly as good as a purely 'snowmobile use' developed oil.
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.
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, but the insurance carriers were happy.The combination of non-metallic 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!
This is almost exactly the same situation that developed with the American Petroleum Institute (API) and the Automobile Manufacturers. They were dealing with legislation that mandated exhaust emission systems to last a certain mileage under warranty and catalytic converter failure was known to be linked to the zinc-phosphorus content in motor oils. The API, in response to the auto makers, soon mandated restricted levels of these additives and is slowly lowering them. The problem was that motorcyclists depended on these zinc-phosphorus additives to protect their higher reving motors from damage and they were a victim of a legislation that did not even apply to them (very few motorcycles have a catalytic converter). Now snowmobilers are victims of this exact same legislative situation, the elimination of phosphorus from two-cycle oils. But they do not need to be! Why? Because motorcyclists and snowmobilers can buy motorcycle oils and snowmobile oils and bypass the restrictions placed on automobiles and outboard boats.
Sea-Doo and Ski-Doo didn't go with the NMMA, they refused to allow their engines to be destroyed and recommended to their owners NOT TO EVER USE TC-W3 oils! Polaris bought the TC-W3 sales pitch at first, recognizing an inventory advantage to having only one two cycle oil to be used in their watercraft, quads and snowmobiles. But they soon discovered the same problems many had already found with the TC-W3 oils when used in a sled. Ring sticking, exhaust port blocking and low temperature flow problems. Suddenly all those advantages of the TC-W3 oils they read about from the additive maker's brochures weren't working out when weighed against all the engine failures! Have you noticed they have gone back to purely snowmobile developed snowmobile oils? Currently there are not any snowmobile OEM's recommending the outboard NMMA TC-W3 oil, and there is a reason for this. They are not acceptable in today's powervalve equipped snowmobiles! Only oil companies with little actual knowledge of snowmobiles and their specific needs continue to try to sell snowmobilers an outboard oil for their snowmobile...and this is because they have a vested interest in doing so...economy of scale by combining several markets into one and selling just one oil. Do not fall for their sales pitch!
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. They tested over 250 samples of two-stroke oils worldwide and used the survey results to establish these engine tests. 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. These tests have a much closer connection to actual snowmobile engine applications compared to TC-W3 tests which are all conducted on raw-water cooled outboard engines. And for the first time ever, an oil can fail the test if it smokes too much!
The detergency test evaluates the oil’s ability to maintain the cleanliness of critical engine parts, including exhaust power valves. This is very important on power valve equipped Rotax, Yamaha and Polaris engines. The lubricity test measures two things. First, the engine is run with a load for 50 minutes then the cooling system is disconnected for ten minutes and the resulting drop in horsepower is recorded. This cycle is repeated several times and each drop in power is compared and it must not vary more than a specified amount or be more than a specified amount. Then the engine is run with increasingly leaner oil ratios: 60:1, 100:1 then 150:1. If no seizure occurs and power is maintained within a specified percentage, the oil passes. The initial torque test measures the engine’s startability when cold, an important consideration for 3-cylinder sleds.
The exhaust blocking and smoking tests are run by mixing the test oil at an over-rich 10:1 ratio and running it in a two-stroke portable generator. The exhaust is channeled into a chamber where a photo cell measures the light that can pass through the smoke. It sounds crude but it works! Finally, a real world test to measure exhaust smoke from two-stroke engines! The exhaust blocking test simply examines the pencil sized exhaust outlet for carbon blocking. At a 10:1 ratio, these tests are very hard to pass. The highest JASO rating is FC. Lower ratings are "FB" and "FA." An even higher "FD" rating could be seen in the future. Most TC-W3 oils will not pass any of these tests!
In Europe, European two-cycle engine manufacturers were simultaneously working on two-cycle oil tests to separate the cheap, poor quality oils from the top quality oils. They tested the JASO reference oils in European engines and their top reference oils in Japanese engines. 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" for minimum test standards. Then, they developed the "GD" detergency test to run hotter and longer (3 hours vs. 1 hour) than the JASO detergency test. Oils passing the new ISO quality level, ISO-L-EGD would be superior to any previous two-stroke oils available! Of course, it didn’t take long for oil manufacturers to develop and test oil formulations that pass this new quality test, and most of them involve using synthetic base oils. Running these tests is a very expensive and time consuming effort but in the end, a bottle of oil with one of these JASO FC/ISO- L-EGD certified ratings means that the oil meets the highest quality tests set by the engine manufacturer in Japan and Europe.
Polaris, had recognized the "all-in-one" advantages of TC-W3 two-stroke oil, and recommended the use of TC-W3 oils in their watercraft, quads and snowmobiles for several years, have recently taken Ski-Doo's position....don't use it! Basically, specially formulated snowmobile oils that pass JASO FC/ISO-L-EGD and do not follow NMMA outboard engine additive restrictions will provide much better protection for higher rpm applications (snowmobiles generally rev higher than 6,000 rpm) and still provide a superior lubricity and detergency than TC-W3 oils at the same cost with less smoke. So, use snowmobile oil in your snowmobile and outboard oil in your outboard engine.