1994 Nissan Sentra Engine Oil

Engine Performance problem
1994 Nissan Sentra 4 cyl Automatic 207500 miles

My sentra has been using up alot of oil latley. I use it to go to work everyday about 30 min away. I go up and down a mountain to and from work. I usuall put valvoline 5-30 engine oil. And I do the oil change frequently. I resently had all the hoses and and selents replaced. The oil was using up quickly before and after the work was done. I trust the mechanic and he gaurantees me his work, I take in the car when it needs anything to him and I am always satisfies. Might I be using the wrong oil? Thanks