No one addressed the "109,000 miles" factor. Seems to recall some posts about flushing or the Synthetic acting to loosen deposits and having a negative result. Frank
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i will address this part. i've not had any trouble on engines that were low miles (under 30,000) but i did convert a 5.0 at 55,000 miles to synthetic oil. it was my dad's car and he changes oil when the moon turns blue. he bought the car new and it had a few oil changes. i say few, because he changed the break in oil around the 8,000 mile mark.
anyway, on with the story, all went well with the engine until the
115,000 mile mark. came up to a stop light, the oil light started to flicker. 10 miles later the oil light was bright red, but no engine knocking. finally ended up taking the oil pan off of it only to find the sludge that had built up in the first 50,000 miles had dried out and formed hard crystals. looked some something like large coffee grinds and rock hard. stopped up the sump. cleaned it all up and everything was fine for 4,000 more miles, when the same thing happened. drop pan, same thing. concluded that the synthetic oil draws the oil out of the sludge leaving the carbon crystals. so, my recommendation, if you have a sludged up engine, keep mineral based oil in it and enjoy the engine, unless you want engine troubles down the road later.
~ curtis
knowledge is power - growing old is mandatory - growing wise is optional