Synthetic oil question

Howdy folks, I'm brand-new to group and recently purchased an '89 Crown Vic ex-fire chief car 5.0. Runs like a champ and mech rec. synthetic oil since "it has
large oil ports". He says engine is very clean after redoing valve cover gasket and can handle the 20-50 weight. Using Ams Oil and have heard good and bad about it for 80,000 / 14 yr. old engine! Any opinions and thanks for the feedback. Happy New Year. (Put a '54' on the back in honor of the old show you old-timers may remember!!!)
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Do not run 20W50 in this, I think it calls for 10W40 or 5W30, check your owners manual. Synthetic or not, change it regularly. Find a new mechanic, large oil ports have nothing to do with anything. Mechanical tolerances affect oil flow. Ask him how 20W50 will flow into the roller bearings for the cam. One tip, change the screen under the PCV valve when you change the valve, it will cause the gasket on the back of the intake manifold to fail if it gets plugged and will leak oil.
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At the risk of getting my a$$ flamed from all of the Amsoil devotees out there, here is my $.02 worth. I used to use Amsoil and liked it very much. I think it's a good product (and my father-in-law was a distributor). I also think it's way over priced and over-sold to the consumer. It won't work magic and it won't make an old engine new or make an old engine last longer. Once the wear is done, it's done, period. That being said, here's my advice. I would use either a synthetic blend or a straight synthetic such as Mobil 1. If you have a Wal-Mart near by, a complete oil change with Mobil 1 will cost you $30.00 total, including a filter. You can't beat that with a stick. The advantage of using the Mobil 1 at this point in your car is that it doesn't thicken much in cold weather making starts very easy on the starter and electrical system. The advantage there is pretty obvious given the age of the components in your car. Second, in warm weather, Mobil 1 resists burning and thinning better than dino juice. Amsoil will do all of this too but Mobil 1 will do it cheaper and every bit as well. I doubt that your engine will last longer than it would if you just changed oil regularly using 10-40 but synthetic does tend to clean better and resist carbon build up. All of that being said, there is no advantage to using synthetic if your car uses oil. In fact, synthetic may cause it to use slightly more oil due to its greater detergent factor and its better low temp flow characteristics. So, the choice is yours. If you go with synthetics however, keep this in mind; I would not use 20-50 when using synthetics. It simply isn't necessary and really goes against the idea that you want lots of flow at low temperatures. 10-40 will be more than enough. As to the large oil ports, well, lets just say that while the mechanic means well and is telling the truth, the ports really are nothing special. The 5.0 engine uses larger ports so that it can move larger volumes of oil more quickly. This engine has a number of applications that include some heavy duty towing and hot rod use. So, large ports are dejure. But, it should be taken with a grain of salt that these are special or require special treatment. All larger displacement engines use larger ports than smaller displacement engines. The fact that they're larger does not mean you should stuff heavier weight oil through them. 10-40 or 10-30 synthetic oil will be just fine and you may in fact, see an increase in fuel mileage on the order of 2-3%.
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R. J. Talley
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