What do I do with this samurai?

Hello,I very much hope that someone is here who can help me with my car. I have a Samurai SJ (santana) built in 1996, and actually I find it quite good, BUT: 1.I find the consumption incredibly much, in winter so 12 liters on 100km otherwise so 10 -12 without four wheel-so my first question, is this normal, because I actually thought it would be about 8 liters. 2.An even bigger problem,when I bought it, was told totla good also in winter,but since autumn I’m really afraid to drive a car, all if it rains, the car is already slipping across the road! You don’t need to talk about snow, I can’t understand it somehow, that’s an all-wheel drive and it’s sliding more than any other car, but my workshop thinks it’s normal, but that can’t be right? I don’t know if the tires are probably to blame, because they’re not so good Roadstone SB 700. I hope anyone can help me there or I’ll be in the ditch soon or I’ll have to take the bus! Thank you before