for thos who do their own maintenance on their trucks, i have a few ?'s for you. Is there a negative to using synthetic oil in an old engine(168,000 miles)? will it cause any leaks? and when changing the spark plugs, which i believe i have to do soon, can you replace half of them at a time? the reason i ask this is becasue i can only get to 3 of the six plugs through the dog-house in the van, the other 3 have to be gotten from removing the wheel well. I was going to take it to a local garage to change the other 3, as putting it on a lift makes it so much easier, but due to the insame amount of work involved it costs a lot of money, so by doing 3 myself i save a little bit. thanks guys, i know that those questions are a bit weird.