About a year and a half ago I switched out all my fluids to AMSoil brand synthetics and WOW, what a difference! Immediately afterwards the ride and the shifting were noticably smoother, even though I had done all the scheduled maintenance with the types of products recommended by Isuzu.

More recently I've "downgraded" my oil to Mobil1 because I can get it for a lot less than AMSoil (about $20 for a 5-Quart Bottle at Walmart) and haven't noticed any difference. Although my research indicates that AMSoil is a superior product, Mobil1 also performs very well and is probably more than adequate for the way that I drive and maintain my VX.

I suppose synthetics may not be worth the money for your beater car, but this is your VX we're talking about here, man!!