is not enough. You also have to consider stability which is related to height and base size. Using a 3 ton jack stand, you have to raise it almost to its maximum height. Floor hardness (concrete vs asphalt) and level of the ground will affect its stability. When I tried my 3 ton jack under my Highlander (3.5L), I had to pull it up all the way. I did not feel comfortable, so I gave away my old jack and jack stands to a college student and bought a set of 6 tons. Anytime, I use my jackstands, I assume they may collapse. You don't want to assume they may be safe.
Please also keep in mind that front side of your car are much heavier than rear one.
