Decision problem…

So after I no longer want to have my 88er 626 GD brought through the TÜV for 1,000,- Euro with my Mazda dealer, I looked for another Mazda with him: Xedos 6 2.0l V6 Bj 93 160.000 km 3.600,- 626 2.0l Bj 95 70,000 km 3.000,- The 626 is with my insurance in the quarterly payment still good 20,- Euro more expensive for this the Xedos should swallow more (12l) and then even Super. As Azubi I have to pay attention to the money and now I am pondering which of the two I take. The Xedos is cheaper in the insurance and has a greater chance for longevity with the 6 cylinder, but has already a lot behind it. The 626 would be cheaper with the financing and in the fuel and has less km on the hump, which with the 4 cylinder however is already a lot. Can someone give me some good and more objective advice?