I've been told by someone who should know that Amsoil is a top synthetic oil. Does any one have a reason that this mght be the case.

 

whats the answer? thanks

 

Well all oils are not the same Ive used Ams oil and I loved it but that was when it was a real effort to get and it cost (back then) a little more soooo I switch back to mobile one when I heard that they changed the "formula" also back then I was still under warranty and I was told that if I had any big proublums they would check for the manufacturers "suggested" oil. Since then Ive started downward spiraling path of god help me,......"drag racing" and these guys that are a lot more serious than I am say,.. "royal purple" and some of these guys act like money grows on trees, so they by it I know, becouse they believe in it!

 

Here is what I found out.
There is an oil specification that, when the specification applies to the oil you use, the oil doesn't have an ingredient which reduces wear. The lack of it results in damage to mechanical parts over time. In some instances the time is alarmingly short. Some auto manufacturers don't require the use of the improved oil and simply say that any oil meeting the (API SM) specification is adequate. I am told that Corvettes need oil which is not limited by the (API SM) specification. I am advised that Amsoil SAE 10 w 40 Marine Synthetic Motor Oil for the motor, Plus Amsoil Severe Gear Extreme Preasure Synthetic 75 W 90 for the differential, plus Amsoil ATF for the transmission has the nesessary specifications for proper lubrication for the C5. Other oils may be equally as good. Please verify all that I have said, because I'm drowning in technicalities.

 

good stuff

 

After I lost a motor in my first season of SCCA racing in 2003 (while running Mobil 1), I spent hundreds of hours online trying to determine the "best" oil. I primarily was looking into Royal Purple and Redline, but discovered AMSOIL in the process. During this search I learned more than I ever wanted to know about oil and over three years later I'm still learning. After reviewing hundreds of used oil analysis reports and other online tests, I personally came to the conclusion that AMSOIL performed better than the other oils I was interested in for various reasons. For a sample of these tests and a few real world used oil analysis reports, please take a look at the tests on this page of my dealer website:
AMSOIL Performance Tests

The reasons one oil performs differently than another are numerous, but primarily boil down to:
- Basestock. An oil's main constituent is its basestock. I've pasted a primer on this below, but the short story is that there are five groups and most synthetics are Group III oils. AMSOIL is a Group IV with Group V additives. This makes a large difference in performance.
- Additives. The amount of anti-wear, detergent, dispersant and other additives that the oil company adds to the basestock varies widely from manufacturer to manufacturer. Based on used oil analysis reports, I feel that AMSOIL uses higher levels of these additives than most other companies.

Downside to the above is that the basestock and additives AMSOIL uses cost slightly more than other companies and thus AMSOIL is slightly more expensive than other synthetics on the market. But for preferred customers (see link in my sig), the price really isn't that far off what you can buy at Walmart.

FYI, I chose AMSOIL and have been using it in my Z06 on the track since 2004. About six months after I started using it, I became a dealer.

Group I base oils are the least refined of all of the groups. They are usually a mix of different hydrocarbon chains with little or no uniformity. While some automotive oils use these stocks, they are generally used in less demanding applications.

Group II base oils are common in mineral based motor oils. They have fair to good performance in the areas of volatility, oxidation stability, wear prevention and flash/fire points. They have only fair performance in areas such as pour point and cold crank viscosity. Group II base stocks are what the majority of engine oils are made from. 3000 mile oil changes are the norm.

Group III base oils are subjected to the highest level of refining of all the mineral oil stocks. Although not chemically engineered, they offer improved performance in a wide range of areas as well as good molecular uniformity and stability. By definition they are considered a synthesized material and can be used in the production of synthetic and semi-synthetic lubricants. Group III is used in the vast majority of full synthetics or synthetic blends. They are superior to group I and II oils but still have limitations. Some formulations are designed for extended oil changes. AMSOIL XL Motor Oils, Castrol Syntec and many others fall into this category.

Group IV are polyalphaolefins (PAO) which are a chemically engineered synthesized basestocks. PAOs offer excellent stability, molecular uniformity and performance over a wide range of lubricating properties. AMSOIL SAE Synthetic Motor Oils and Mobil 1 primarily use group IV basestocks. PAO is a much more expensive basestock than the highly refined petroleum oil basestock of Group III.

Group V base oils are also chemically engineered stocks that do not fall into any of the categories previously mentioned. Typical examples of group V stocks are Esters, polyglycols and silicone. Redline uses an ester basestock.

 

As a caution, I said in another thread, specifically relating to track use (not for cars under warranty) that I use the 10w40 Synthetic Marine Motor. While your discussion is fairly accurate, keep the following in mind:
- The C5 owners manual requires an oil meeting GM Standard 4718M. It also requires a 30 weight oil. (Note that the 10w40 Marine Motor oil mentioned above meets neither of these).

For street driven C5s, particularly these under warranty, these AMSOIL oils are recommended by AMSOIL for the C5 and are labeled for use where GM Standard 4718M is recommended:
AMSOIL Series 2000 0w30
AMSOIL SAE Synthetic 5w30
AMSOIL SAE Synthetic 10w30

The Series 2000 0w30 is a very good oil and is what I will use in my new 2006 CTS-V when I get to my first oil change (currently at 52% on my Oil Life Monitor), but the 5w30 is also a very good oil at a more reasonable price.