My son and I were talking about new cars recently and it's his opinion (I'm not sure if I totally agree with him) that all other things (gas mileage, expense, etc.) being equal, if possible it's a good idea to get a larger engine, if available, because it'll work less at powering things like A/C, PS, etc. and thus last longer. There's also the "fun" factor, but I assume that's more important to my son than to me. Is this a good rule of thumb or obsolete?