You don't need no quarter-cup of oil. Use water-packed, spill out the water (it's great for soups!) and add a spoonful of olive oil.
water if you want to eat fewer calories. however, the oil-packed tuna is much yummier.
Water. Oil is disgusting and completely unnecessary. You may as well go to Mcdonalds.
Water.... oil makes the tuna tastes oily and gross :)