Thanks, Gilly. The stuff I bought did not appear to be the synthetic stuff. It was in a blue bottle with a white top, and as I recall was about $5 a bottle -- unlike the $20 they wanted to charge me for the synthetic (silver quart bottle). I did use it for my 3.5 quart change two years ago with no ill effect. I guess if it's Dexron, it would be marked as such, wouldn't it? I'd just as soon put in all one brand though, so maybe I'll use these four quarts in something else.