I bought my 94 with 114K from the original owner who always ran penzoil or some other crap on sale along with a fram filter. I bought it in September 03. I switched her over to 10W-40 AmsOil and a Toyota filter. Let me tell you how black it got and how fast! I just changed it yesterday (7 months 10K later) again... same set up... toyota filter 10W-40 Amsoil and NOW she's running differently....better:) Wouldn't know how it runs on regular oil..never ran it in my 4runner. I do notice 1 thing now since my change yesterday.. about 6K afer the initial change i started losing oil pressure at idle. Well, that's due to so much crap in the filter!! I now have my oil pressure back at idle! That's how much crap the AmsOil was flushing out.. it actually was clogging up the filter. I also did notice the valve noise got quieter after a few months of running it. I LOVE AMSOIL! My engine had a lot of deposits in it. We'll see how fast this 2nd change gets dirty. I deffinately reccomend a Synthetic Oil.

Just to let you know.. Castrol Syn isn't actually synthetic oil. It's regular Oil that has been "highly filtered". Mobil 1 sued castrol a few years back. Castrol won the law suit b/c the laws state that synthetic just means X amount of "man interaction". So if they filtered it enough.. it's been man handled enough to be called synthetic. I'd switch to Mobil 1, AmsOil, Royal purple or redline. Just my 2 cents.