I doubt that it matters but I'm surprised about the 'not for water cooled engines' part. The TCW-3 rating is by the BIA (Boating Industry of America). I haven't seen an air cooled boat motor in a very long time.
Actually I didn't intend to imply 'not for water cooled engines'. I said 'watercraft' and meant to say 'personal watercraft (PWC). And, also, it seems I got confused. The TCW3 rating is a NMMA rating (National Marine Manufacturers Association). I had read a long article I came across http://www.sea-doo.net/techarticles/oil/oil.htm, and got mixed up on the NMMA TWC3 rating and the API-TC (American Petroleum Institute) rating. (And if you read the article only once in its entirety, you may be able to see why I got confused.)
For PWCs the author is suggesting sticking with API-TC rating which is less common and more expensive than oils that are TWC3 rated. And after re-reading, my conclusion is that the TWC3 oils should be fine for a water cooled rotary. Some highlights are given below.
What mix ratio are you guys using?
Al
"Ashless detergents are used in low temperature applications such as TCW3 oils where the ring land temperature is held below 300 deg/f. These detergents work well in engines where an excess of cooling capacity is available and power valves are not used. Ashless detergents are manufactured form organic nitrogen compounds (Hydrazine) instead of heavy metal compounds; therefore, they produce no ash as they are burned away. This is where the name "Ashless" comes from. Oils containing this type detergent have a characteristic Ammonia odor. Ashless detergents were used in the first generation of Bombardier XPS engine oil. The formulation was later changed to a low ash type detergent because of the higher temperatures generated by the 787 engines.
Low Ash type detergent/dispersants are used in most API-TC, Jasco FC and ISO GC certified 2-stroke oils. These oils are designed for air-cooled high performance engines that operate under severe load/temperature conditions. Low Ash detergents can keep the deposits to a minimum at ring land temperatures as high as 400 deg/f. These detergents are manufactured from compounds of Calcium and Magnesium (heavy metals). After these compounds (Calcium Phenate or Magnesium Phenate) do their job, they burn away, forming a heavy metal salt (ash) that is swept away during the normal combustion process. Hence, this is where the name Ash-type detergent comes from. Ash type detergents depend on the higher combustion temperatures (787 and 951 engines) to keep the resulting ash swept out. Therefore, the use of these high performance oils in outboard or other mildly tuned 2-stroke engines is not recommended.
Some manufacturers are using a combination of detergent types (Ashless and Low Ash) to provide a broader range of uses for their oil. It is important to note that oil designed to meet TCW3 specs. only (Ashless) will not protect an engine requiring API-TC (Low Ash) type oil. The converse is also true. Using a Low Ash oil in an engine designed for an Ashless type oil only could result in fouled plugs and gummy combustion chambers.
I hear a lot of complaints about the high cost of some 2-stroke engine oils, mostly Bombardier XPS. Well, I have to agree, it isn't cheap, but neither are any of the other API-TC oils compared to the TCW3 type oils. Unfortunately it just costs more to manufacture API-TC oils than TCW3 oils. Despite its relatively high cost, I cannot recall any Rotax engine failing because of XPS oil. XPS oil was a joint development of Castrol and Bombardier. Bombardier wanted a 'universal' high performance engine oil that they could use in all their recreational products. That meant oil would flow freely at –40 deg/f and still maintain sufficient film strength at 350 deg/f. The first generation of XPS (1995) was formulated using Ashless detergents; this allowed the Rave valves in the then new 787 motor to stick. The formula was later changed (1996) to a low ash detergent that eliminated the rave valve sticking problems. There have been several minor improvements in XPS since 1996. Castrol remains the only manufacturer of XPS. This is a proprietary blend sold only by Bombardier. There are a number of good API-TC type oils out there if you chose not to use XPS. If the oil you want to use does not have the ATP-TC certification on the container, contact the manufacturer. Most of them will be more than glad to provide you with information on their products.
Do not use TCW3 in your SeaDoo PWC. I don't care if it's a full synthetic or your brother-in-law uses it; for the reasons stated above, it will not protect your motor when conditions get tough in your motor.