I would like to play the devils advocate here and I am also a diehard Amsoil user for many years in everything I own from my motorcycles to my drag race engines and have found nothing better. A while back I found a site called Scamsoil and figured it was just some hack site doing nothing more than bashing synthetics and Amsoil specifically. What I found was a pretty knowledgeable guy taking all comers and countering their comments and claims with facts and educated answers. Below you can read the reply I got when I emailed him about his take on the differences between castor bases oils and Amsoil synthetic oil and the best oil to run in my 95 Honda CR500.
Quote:
Brian Dobben - BSMET
DMT Technical
1.
Without a doubt, the oil industry, the "lubrication engineers", and the OEM's are dominated by mindsets created by two groups with agendas: the petroleum oil companies, and the OEM's. The oil companies want everyone to buy petroleum products. The OEM's want their products to last as long as most consumers think they should without breaking down, with warranty periods set shorter than that. For that reason, the petro companies have invested a great deal in their controlled versions of educating mechanics and dealers and engineers. In the glaring history of this situation, it's crazy to think that anyone can get an accurate picture without considering the perspective of the company considered to be the worldwide standard in synthetic lubrication. So I applaud you for wanting to investigate Amsoil.
2.
The API's agenda is written clearly for all to see, that they exist to promote petroleum interests. And it's very telling that their API starburst certification licensing program specifically excludes high performance lubricants, certifies only to bare minimum performance levels, and does not provide ANY method of rating the comparative performance of oils - even though the ASTM tests clearly provide measured values. You can do a search on "Amsoil Scam" and read a lot more I've written on this, in an extensive Q & A you'll see listed on my main website. This is a direct link to the page:
http://www.ultimatesyntheticoil.com/Scamsoil_Skeptics.htm
3.
The main key to understanding the discussion of castor oil is the word "esters". Adding castor oil was, a decade or two ago, a good way to get improved performance in some 2-cycle applications where there weren't good products engineered yet. But as he notes, castor oil has a lot of content downside that can get you into trouble. Esters are a large group of lubricants that provide quite a range of performance in different lubrication applications. There is real value in getting certain advantages of specific forms of esters in engine lubrication, but the value is maximized when you deliberately engineer that chemistry so that you maximize your advantages while avoiding or minimizing any of the downside. And THAT is the thinking behind many of Amsoil's formulations, and a key to their dramatic superiority when compared to other synthetics. That is also the reason behind having multiple four-cycle oils, multiple diesel oils, and multiple 2-cycle oils: you optimize the performance of both the base stock and the additive package for the application(s) you are targeting. Many AMSOIL products have a small optimized amount of a pure ester type(s) whose performance has been selected as being nearly ideal for that particular application, bringing advantages while avoiding disadvantages.
For example, taking this overview down to where you "live" with your CR500... here's my newest website in development:
http://www.vtwin-hd.com/d.cgi/1220579/home.html
If you go there and click on the left hand button for "2 Cycle Oil", it takes you to a page comparing and listing the different Amsoil oils. You can click the link on each one for "more information", but even just reading the overviews you can understand what these oils are targeted for. The reason for these various formulations is that there are several ranges within 2-cycle applications for ring and piston loading, ring temperatures, combustion temperatures, exhaust valve temperatures, rpm range, and primary load/rpm use. Most synthetic companies make one product and imply that it's the best for every 2-cycle application, while the truth is that it's probably a performance compromise in all of them. All of that means that the AMSOIL product descriptions will give you a good idea of what's most likely to be the best formulation for your bike.
But it also means that depending on how your bike is "set up" and how you use and ride it, either Interceptor or Dominator could work the best for you. Either one WILL work, and if I were you and the product descriptions don't clearly address it for you, I would try both of them and see which one seems to perform best overall for your riding in the aspects that are most important to you. But having said that, if you run very high rpms at full load in a racing application with a highly modded engine, that's where Dominator could shine brightly for you.
For someone to say that an Amsoil 2-cycle product is "junk", simply means that the one they tried for that "bad experience" application wasn't a good match for the engine's needs in how it was being used. For example, the Canadian Forrestry Service standardized several years ago on Amsoil's Sabre Professional 100:1 for their chainsaws, and the performance in those applications is way beyond anything in the market, leading to lower fuel costs and tremendous increases in the service life... because that's exactly what it was designed for. However, that doesn't mean that the product will work well in a dirt bike, a snowmobile, or a jetski.
The fact of the matter is that over the last 5 years especially, Amsoil has completely taken over most of the competitive racing venues. Xcross, Motocross, Snocross, Champ boat, Offshore, Diesel competitions... you name it. And of course, Daytona Bike Week and Sturgis. It's not a matter of spending advertising dollars, but of Amsoil realizing that there is real value in them sponsoring these segments where 95% of all the competitors are using AMSOIL lubricants.
I've subscribed to Diesel Power mag since about its' third issue, and I found it interesting that in their coverage of last year's national Diesel Power Challenge, they happened to mention that every competitor in the event was running Amsoil. I find it interesting that the recognized national expert in high performance Corvette engines openly recommends Amsoil without advertising compensation. I find it interesting... well, I could go on for a long time.
I guess in concluding, I would make two points. First, a true synthetic is always better than a petroleum product. Second, when comparing performance among synthetics, only superior engineering will produce the superior results: there is nothing accidental about it, and the effectiveness of sex-based, ego-based or confidence-based marketing campaigns adds nothing to performance. For decades, the picture has never changed. Only Amsoil publishes their performance against competitors, and only Amsoil is constantly updating formulations to include the latest performance improvements in additive and basestock sciences.
I guess it all comes down to what you trust and why. For me I won't use anything but a true synthetic that is tried and tested in nearly every motorsport known to man.