A rusty 17mm nut may need the next size up wrench in order to be
able to fit it, I've had this happen, its not bad idea to have those
odd size wrenches

If a nut is so rusty you can't get the correct wrench to fit, it's probably
time to take other measures. Wire brush the rust, apply penetrating oil,
maybe apply heat, use vice grips, etc.

I've worked on vehicles using every one of them (not all on the same
vehicle) - I'd have been totally lost without a minimum of 8, 10, 12,
13, 14, 15, 17, 18. 19, and 21 mm
On Toyotas the 11 and 13 and 18 were not required - on American iron
the 10 and 12 are pretty much redundant - along with the 17, I
believe.

On Volkswagens, the most used wrench sizes are 10mm, 13mm, 15mm, 17mm, and
19mm.

However, brake bleeders require a 7mm, 8mm, 9mm, or 10mm wrench, depending
on the brand and location of the bleeder.

I also need an 11mm wrench to remove my carburetor cover.

I think the front strut nuts need a 22mm wrench.

12mm, 14mm, and 18mm are probably the sizes I use the least, but
occasionally I'll run across a fastener than needs those too.

Anthony Watson
www.watsondiy.com
www.mountainsoftware.com