You don't need the traditional "wrench". If you see the oil filter(driver side of engine) you will notice that you only need a regular box end type wrench to loosen and remove the bolt. This attaches the oil cap to the main oil resevoir tank. I have only changed the oil once and can't remember exact size, but P used a pair of channel lock type pliers to loosen it. Mine wasn't too tight so it was easy to loosen in the tight space .Also make sure you put the filter into the top cap first to make sure it is properly seated. Once you have it in the filter should stay inside the cap without you having to hold it. I made that mistake the 1st time and it mashed the filter when i tightened the assembly down.. do not over tighten the nut and squeeze the o-ring, this wwill cause a leak. Remember there is a rubber O ring around the cap when you remove it. Hope this helps.