With 175K miles use whatever you can afford. I'd stick with regular dino oil with that kind of mileage. I have a jeep the same age, but with 54K on it, and I should get synth, but I'm wavering! When I do the first oil change I'll decide.
You have a theoretical longer life between changes with synthetic, but on a "high" (yeah its a jeep but) mileage vehicle, it's not going to gain you much.