My cousin has a `97 Ford contour with about 100k on it. He bought it last fall and hasn't changed the oil yet. I'm going to take it to get it done at some point (not a priority for him), but was wondering what oil to use, as the car does seem to leave some oil spots. He doesn't check the oil, so I don't want it to be something that burns off. Ford called for 5w30, but I found that whoever changed the oil last (previous owner right before he bought it) used 10w30 (but I don't know what brand or type). The car sits outside in the winter and doesn't get any/much warmup. He also rides it pretty hard, even when it's cold. So, what conventional or maybe high mileage would you use for him and 10w30 or 5w30? I know that it doesn't ever get checked so I don't want it to leak too bad for him. What would you do?