As you can see from the recommendations from Tire Rack, probably slightly higher pressure up front is preferable because the car will be nose heavy. The rule of thumb is that you increase pressure as load increases. Pressures need to be higher on very thin side walls, ie: big wheels and low profile tires. If you look at the sidewall ratings, the max pressure listed is also at the max weight rating for the tire. Since your car never approaches the weight limit of the tires, pressure should go down accordingly. Over inflating will barely increase mileage, but it's still at the expense of tire life, it doesn't help. All you'll get is tires worn in the middle and less so on the sides. In the end, the correct pressure is that which gives the most even (and longest) tire wear. On a 285/20, I'd probably start around 36 psi and go up from there until it tends to wear in the middle and/or ride quality is rough. Anything lower than that and you could be risking wheel damage if your roads aren't smooth. Everyone should take the time to experiment with pressures a little, you might be surprised at what actually works best for you and your car. I'll bet it's not what's on the sidewall.
