Petroleum or Synthetic ATF?

[Quicksilver Vert]

With 5 years and 24000 miles on my 4L60E transmission,I want to do a fluid and filter change just to keep things working right.I'm thinking about using a synthetic ATF like RedLine,Royal Purple,or Mobil 1 when I do the change.
My transmission temperature usually runs 160-180 degrees,and ocassionally gets as high as 200-210 degrees in slow moving traffic.
What are you guys using and having good results with?

[rotwiler]

I always use regular ATF, no synthetic. but I use synthetic on everything else on the car. I have always heard synthetic in the 4L60E causes slipping etc... a guy on the race team I am on is the local tranny/f body guru..tuner, tranny builder etc, works for a tranny shop and said don't use synthetic.. All the local 10 second guys have him build the trannys and never a problem...so I'd say stick with regular dino oil. A tranny cooler would probably be good, with the normal hard use they get. Who can just drive a car with the LS1 in it, even my wife has to nail it to the floor every once in awhile. :)

[0rion]

even my wife has to nail it to the floor every once in awhile. :)

That's funny. My wife is the same way. She drives a Durango all the time and if for some reason she takes my f-body or GTO somewhere she hammers it leaving the driveway with a huge smile on her face. I think she's harder on the cars than I am. :D

[Quicksilver Vert]

Thanks Rotwiler,thats just the kind of info.I'm looking for.Sometimes doing what you might think is best for your car,like switching to more expensive synthetic ATF,does more harm than good.I'm sure your tranny expert friend has seen enough of these apart to recommend not to use synthetic.