Back in the 60's and early 70's, I always used Quaker State Super Blend in 10W-20W40. and no oil change was complete without adding a can of STP. When Mobil 1 came out in the mid 70's advertising one year or 25,000 mile oil change intervals, I switched over to it and went on a yearly oil change regime until I retired about 5 years ago and my yearly driving mileage came down from 18,000 to 20,000 miles a year to about 6000 a year. I also quit using any oil additives then(when I began using M1), and have not used any in more than 30 years. Since I have gone to 6000 miles a year, I use conventional, most any brand, changed twice a year.
Bu the way, in the 30 years I used M1 in my cars, OCI one year, there was never a lubrication problem and my engines were always as quiet when they had as much as 140,000 miles on them as when new. I always wondered, when they came out with Mobil 1 Extended Performance, just what they had done to it to make it only good for 15,000 miles; now, since it is not really a true synthetic in the old sense, I guess we know.
