Reaching A Living Balance

I share an appartment with a friend of mine and when it comes to costs, of course we try to split things evenly. Unfortunately, we aren't seeing eye to eye, but know the most efficent way to do this is to reach and equilibrium. Rent is 500 a month, cable and internet is 65, electric 90 and other expenses like food and toilet paper are about 100 a month. Now, I don't have a car so i use my friend's quite frequently for errands and such. He believes i should cover the total amount of rent (500) instead of half (250) as a car payment to him. He pays for gas and oil and car maintenance, then we split the rest of the living costs (cable, electric, food, etc.). Do you believe this is an efficent way of doing things? He argues that this will in turn help us reach and equilibrium because my oppertunity costs will be much less than actually making a car payment (taxes and gas) . . . or am I just being had?