this is the test I used when I owned my trucking company. I did this infront of both the Amsoil rep and the Royal Purple rep. I was testing the Amsoil rep's claim that amsoil would reduce engine vibration. I tested Delvac Synthetic (my pick), Amsoil (whatever the rep had brought to show off) and Royal Purple 15w-40 (brought by the local RP rep, I think he actually came from Chicago for this).
We picked a truck at random and drained out its oil and changed its filter (the truck used was a 2003 Kenworth T-600 with a 475 C15 cat)then poured in the Delvac and started the engine and let it run for 20 min. I put a full pack of cigarettes on the driver side steer tire with the hood up and timed how long it took for the pack to vibrate off the tire.
then we drained it, changed the filter, poured in the Amsoil, and repeated the test with the same pack of cigarettes.
Did the same with the Royal Purple. as we gave the engine 20 min warm up time in a temperature controlled environment for all three tests and any argument that the engine was warmer for 1 test than another is moot.
the pack of Marlboro Blend 27 vibrated off the tire in 31 sec with the Amsoil
47 seconds for the Delvac
over 10 min for the Royal purple.
the amsoil rep went home with his head in shame and I continue to use Royal Purple exclusively.
to b fair the times we used was a best of 5 incase air current made changed or the pack didn't get in the exact right spot...... except the the RP because the engine really did just smooth out right away with it.
this is by far a scientific method, but it is a practical real world test.