A few techs corrected me on a couple of things I missed in the synthetic oil article. When you change to synthetic it is a good idea to flush the engine either with a engine flush additive or diesel oil 15/40. Run the diesel for about 250-500 miles and it will clean out your engine 2 warnings first use a top of the line filter and be aware that a clean engine with high mileage can result in problems. This is not a bad idea no matter what oil you use to keep ypour engine clean.AMZOIL is not an additive it is oil in a category all by itself, normally I would recommend it but in my area it is hard to find.When switching always go up never down if you have been using it for some time. Always use quality oil.When using synthetic use a high quality fuel low quality fuels can cause a carbon build up and this is more prominent when using synthetics. One question I was asked do oils have a shelf life and yes they do 4-5 years. If they go bad they develop a cloudy color and gel up.I apologize for any problems or questions that I raised, no excuse but I was interrupted to many times when writing. Thank You to all who put me back on the correct path.