How much will it cost to fix my mitsubishi eclipse and stop it burning oil?

my 1999 mitsubishi eclipse RS is burning oil. how much does it cost to fix this?|||DONT SPEND MONEY GO TO A SHOPE LIKE NAPA AND BUY A BOTTLE OF LUCAS PUT IT IN EVERY OTHER OIL CHANGE ITS ABOUT $14.99 IT WILL WORK IT WILL STOP THE OIL BURNING