When I had the spring replaced on my garage door (the kind that winds up,
definitely a scary thing to try yourself) the repairman used a portable
impact wrench to remove some of the nuts and lag bolts. Nice tool. Was
looking at getting one for myself. Seems that they come with 1/4" hex, 3/8"
and 1/2" square drives. They 12v models also generate 90 to 100 ft-lbs
torque. I have both 3/8 and 1/2 sockets and it seems to me 1/4" hex is too
small for that much torque and less convenient for sockets. Last time I
changed my oil had a hard time loosening the drain plug. I just drive one
side of my car up on 3 2x6 's I nailed together so don't have much room to
get much leverage. Thought the impact wrench would work well for this
situation.

Any advice on type of drive and brand would be appreciated. Am leaning to a
Makita as I have a 12V portable drill and have seen drives without batteries
and charger for sale on ebay. In the store they are close to $200 so would
like to save some $.

Thanks in advance.