Most folks just know what has "worked" for them and no one really knows the condition of the engine at the time. So, its anyones guess. What I do on a lot of ocassions is to send off for the "lab or test" information by calling or writing the number or address on the can. You would(but not me) be amazed at the claims these companies make from test in controlled
inviroments. Someone mentioned "Restore". That is the last one that I sent for info on and yes, in their test they list the engines/mileage and lots of other info which is good reading. BUT, for the money you spend your wasting your time. Now understand, I'm not against using some additives, but I am against the misleading, or deceptive type advertising used to promote the stuff. I believe it was John Milliman who listed a site not long ago that was real good reading on these additives we pay for when "most" oil already has it in it....and the windfall of profit in it for these companies. Pehaps an additive is good to get you by until the problem can be fixed/repaired but there is no excuse for not performing regular maintenance until something reaches its mechanical limits and then gets a real fix!!
Let me throw some fuel on the fire along a different line.... the oil with the lowest co-efficiency(hope I said that right) is TUFF OIL. These folks will send you info to and how/what test determine the results....which of coarse is sanctioned by the governement....wouldn't you know!!
