Purchased my Jeep Cherokee about 7 weeks ago. Has about 180,000 miles on it. Basic Question to ask. What do you recommend for oil in the oil change? I am guessing Castrol Semi Synthetic with Slick 50 added every 3 oil changes. Its the viscosity rating I have questions about. I drive alot of miles in hot weather , 90 Deg to 108 Degrees in the Summer. Winter would be normally say 40 Degrees to 65 degrees. For summer, would 20w-50 be the way to go. Then in winter, 10w-30 or 10w-40?

Im also going to change the Auto Trans fluid soon too. Now that I am not sure about. Any advice? Thanks.

oil in my owners manual is based on temperature. 10w-30 dino is the recommendation in normal temps but really cold and 5w-30 dino is the recommendation.
that said i run 10w-40 maxlife all year round.

with Slick 50 added .
Imho don't bother with the Slick 50. Save your money, imho.
I used to use it years ago, but I found the contriversy about its effectivenes to be disheartening. Most of the evidence supporting it is simply anecdotal and not scientific. Even after 20+ years, it seems nobody can say conclusively if it has any long-term benefit. I stopped using it and just saved my money and imho, none of my engines have suffered as a result.

These 4 liter engines last a long, long time just with regular maintenance.

10w30 preferred always, and if it's below freezing all the time you can use 5w30. That's what the book says.

Slick 50: I tried it many years ago on a very older car and it seemed to help with mpg, but I didn't see any other benefits and quit using it, much as Rat did, after all the bad press about it.

I've always just changed my oil at regular intervals, never had a problem.

One product you might benefit from is this one (http://www.auto-rx.com/). I can personally recommend it; I've used it on two older vehicles that I bought and it works as advertised, both in engine and trans.

Ok. Now what should I use in the trans?
And where do you buy the Auto-rx stuff? Or only available online?

You can get it on the website; I've never seen it at the store.

Do a search here for the right trans fluid, there are several threads. You could also grab a Haynes repair manual, it'll tell you. Or do a Google search. [I'm not sure for that year]