BigJohn, If you only change one factor at a time then it ireally is not an issue. So if you use LC adn GC one time you should test the M1 with LC as well. THe alternative would be to test the same product agian with ot with out the additive to see if results are either replicated or completely different! You also have to wait for close to the same weather conditons and the sample must be taken with close to the same number of miles etc....
Now if you do not care to make an apples to apples comparsion then you can throw all of that out the window. If all you care about are the end results for your application you can be far less scientific in your methodology. I know if I hit on a winning ocmbination I would not care about scientific method at all! I surely would not continue testing either!
You also have a time factor as well as formulation changes. For example in my case M1R has been changed from the formulation I used! SO even though I plan on restesting it with the same additives that I used before it is going to be two winter from now! The formula has changed and will likely change again between now and then! So what I am really testing in my application is weather or not I can get the same % of additives to disappear from the oil with simalar usage, temp.'s and additives.
I also do not think we make genearal statements about an oil rather what appears to work best in a particular application under those specific conditions! Now if we always see an oil shear excessively or we always see thickening or some other trait we can and do generalize about an oils specific traits!! DOes that make sense? If we see an engine consistently does betteron a certain viscosity or HTHS or type of additive package or base stock we also may make generalizations about that! That is just my $.02 though!! I belive their is plenty of room for almost all oil as they all have thier purpose!!
