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semi synthetic oil to use or not


Having recently aquired my 1965 289  Mustang I am now thinking about dealing with the mucky bits and changing the oil to begin with. I dont know what oil was used last time it had a change and am thinking of 1040 sae semi synthetic oil. any thoughts on if this is the best oil for the engine or not?

I see no reason to use semi-synthetic oil.  If you want synthetic the cost isn't much more.  I would do my initial oil change with a conventional motor oil, then see how quickly the oil darkens up.  If the engine is really filthy inside I would opt to pull the oil pan and clean it out manually.  There are products like Rislone that will clean up and engine, but I don't like them on an engine that is really dirty.

One problem with cleaning out sludge is that it has to go somewhere and all the small passages in the block and crank and lifters can get clogged.  Pulling the pan is a pain in the ass, but it may be a cheap way to extend your engine life.

I agree.  I changed from dino oil to mobil 1 full synthetic a couple of years ago and noticed an immediate difference in performance with my old 289 that had 230K miles on it at the time I switched.  The price of dino and synthetic is virtually the same considering you can put twice as many miles between changes using synthetic.  The  filter makes a difference too.  After a lot of research, I chose the Ford Motorcraft filter.  You can go to my FAQ section at the top of the Classic section and read the oil filter study.  Royal Purple and Amsoil are excellent synthetic oils, but not much better than Mobil 1 that you can get at Walmart.  Get the idea out of your mind of using a blend.  You don't want to use any internal cleaner, because you run the risk of breaking off black gunk and stopping up oil passages.  Just switch to synthetic.  You may get a little leakage at the gaskets at first because the synthetic is so much slicker.  But, that will stop when the old gaskets swell back up.  I use Mobil 1 10W30 with great success. 

Thanks for the help guys


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