Let me attempt to make some sense of these posts. I have owned (with 98% certainty) way more vehicles than a multiple of you folks all together. I've raced, owned a sizable business that required vehicles, and collected over the years. I used to sell Amsoil, and of course used what I sold. Used it in large diesel boats, many motorcycles for street and race, in old classics and new Ferraris. It's a great product, as most popular syn oils are. Over time, with many engine tear downs, observing others dealing with their engine/transmission related issues I have come to the conclusion thru experience and scientific evidence that regular, more frequent oil changes with less expensive products is a better approach. I've has too many vehicles that have encountered fuel dilution at 8-10K miles, and a build up up very fine particles that escape normal filtration. Amsoil with a bypass filter is a great idea. Unfortunately, it's hard to find a home for these guys in many engine bays. At this time I'll get to my point; I can purchase a good API approved high quality product for $4 qt. or less and a diester Euro oil in bulk for $6.50 qt. which makes more frequent changes highly affordable. And, if you're going to keep your lovely ride for an extended period of time, I feel you are far better off following my experience. I've witnessed first hand, Toyotas, 5L, 3.5, 2.7 Ford engines trashed.... not to mention a freight car of small turbo 3-4 cyl turbo engines eaten up by extended oil changes. When you see Toyota 2.5L 4's at 125K miles with locked rings, badly scuffed piston skirts, worn/scared bearings all from following the manufacturers recommendations .... Don't. Their job is to get you past 60K miles without filing a claim. I began using syn oil in the early 70's which was then "Royal Trident" and we know today as Royal Purple. I used it in my weekend racer a modified TR6. I immediately experienced the benefits of advanced chemistry. But, lots of things happen to an engine that the oil itself has nothing to do with. Out of over 75 vehicles I've not experience a single case of oil related failure. I have not repaired an engine, transmission, or diff out of warranty. And here's what you don't want to hear, 95% of all repairs are all or in part user induced. A close friend had a '65 Vette, 327 x 350 HP, 4 speed for 465K miles without a rebuilt. He used Quaker State straight 20W in Winter, and 30W in summer. Straight weights virtually have no VI improvers. Good quality earth juice, now wax removed, has up to 40% syn in light weigh versions will get you thru 100K miles with no problem. I know, I recently sold my '69 Buick "Duce and Quarter" with a 430 Cu.In./365HP and at 54 yrs has never been repaired.
