Me. Using AMSOIL. Change oil at least once a year if I don't do 25K miles on the engine. But I do change the oil filter at 12.5K miles if I go that far by the time a year has gone by.
I had a 1995 Honda Civic, 4 cyl. that I used AMSOIL in. Changed oil every 25k miles, oil filter every 12.5k. The car had 307k miles on it when I sold it and still going strong. Of course, I had to change oil in the car every 2 or 3 months since I racked up the miles pretty quickly. Another car I had that I used AMSOIL in was a 1999 Olds Aurora. It had almost 300k miles on it when my wife sold it. Two other vehicles that I used it on were 1995 Ford f-150 with straight 6, and 1996 Ford F-150 with 5.0 engines. Changed oil every 25k miles and filters at 12.5k. Both pickups are still in service today (not by me, but I sold both of them to a friend of mine who uses them in his business). One has over 400k miles on it and the other one about 387k miles last I checked. If your engine doesn't have an oil leak, then it is a very good oil and economical, too. If you have a leak, it could get expensive.
I have been wondering: I have heard of 4 cyl. engines that were modified to produce 1000 H.P. If that is so, how can I go about getting 300 H.P. from a 1987 3.8L engine (rated stock at about 120 H.P.)?
