… to work on Japanese cars are 8, 10, 12, 15, 17, and 19 mm. I have never had the need for any other sizes.
What can be said for German and domestic cars?
You’re forgetting 14mm. Try doing a Toyota oil change or timing belt without one.
I needed a 17.5mm flare nut wrench for the power steering lines on GM minivan. I have a post up here about it someplace. I promise that it wasn’t supposed to be SAE.
The fittings for the new lines were 18mm.
I haven’t owed a “Japanese” brand since the 80s - not for any other reason that I don’t think they’re worth the extra $$ for the supposed reputation.
So I’ve worked on Ford, Chrysler, and lately GM products. I’ve needed 8-19mm and over, inclusive.
One thing I can’t figure out though is that a lot of metric sets don’t include 16mm. They just go from 15 - 17. Luckily I have a set that didn’t skip 16mm because I’ve needed it more than once.
My guess is that the 15 is a typo and should have been 14. That’s one thing I’ve always liked about the Japanese cars; the commonality of wrench sizing.
My dislike on domestics is the use of the 15, occasional 16, and the 18 MM sizes; usually found on accessories or suspension components.
The European cars are not bad. You seldom see a 12 MM as bolts/nut sizing in that range are usually 13 MM.
One of the oddest ones I’ve run into involved screws on a shaft plate inside a VW manual transmission. These screws were countersunk (deep) and had 5.5 MM Triple Square heads; basically an odd size 12 spline hole.
Some of the old SAABs had a 13 MM bolt on the water pump that was of an 8 MM X 1.25 thread pitch but was left hand thread. This required a special left hand thread tool to remove the water pump.
asemaster — "You're forgetting 14mm. Try doing a Toyota oil change or timing belt without one."You're right. Both Toyota and Honda oil pan bolts are M14 x 1.25 mm.
For Japanese cars you’ll also need 21mm for lug nuts on some models, 22mm for alternator pulley nuts, crankshaft pulley bolts for some engines (like the 1MZ-FE) and for various suspension/steering components like strut retaining nuts. If you ever work on old Mazda RX-7 rotary engines, you will need a 23mm for the oil line banjo bolts. There was even a 16mm fitting nut on the Mazda. Don’t forget 30mm and larger for various axle nuts. Occasionally a 24mm size comes up for chassis/suspension work. I’ve run across a 26mm nut on a Nissan truck front axle and a 27mm for older Nissan crankshaft bolts and other applications (Toyota EGR tube nut). I know I’ve left some out and the applications I mentioned were just those that I could remember off the top of my head. There are plenty more I’m sure.
If you include American and European sizes, I have found a 20mm on older GM FI fuel filters (AC Delco brand). About the only size I’ve never run across is 25mm. As I am only a shadetree mechanic, my experience is limited.
The difference between the hex on most Japanese fasteners and American/European fasteners is the standard used. Asian brands use the JIS standard and American/European brands use the DIN.
My 4Runner has a rather large nut on the front driveshafts…34MM, if memory serves (which it probably doesn’t), but it’s big.
I’ve used a 13 a heck of a lot of times, so that should definitely be on the list.
I actually went through this list with a work colleague a couple days ago…he keeps borrowing tools. Finally told him to just go buy a set and leave us alone. 
My Mercedes uses some and 22s and 14s. Now I need a 7 mm allen wrench that I don’t have.
If you really start digging into the Japanese cars you will find that many more sizes are needed than what was originally stated.
Those 8 MM through 19 MM sizes are just the ones that are used when performing the bulk of the repairs on a daily basis.
Same for domestics and European.
I remember working on my Vega…
With a 1/2 and 7/16 socket you could tear into more then half the engine. It got to be comical…The guy I was helping…we’d get into a new part…“Is it 1/2” or 7/16"…and 90% of the time it was one of them.
The bung plug on my Toyota manual tranny was, if I recall correctly, 25mm.
10, 12, and 14 are perhaps the most common, but you really need a full set from very small to large…in
6pt sockets
12 pt sockets
6 pt deep sockets
12 pt deep sockets
box ends
open ends
"line" wrenches (the box ends with the opening for a fuel or hydraulic line)
ratcheting box ends
etc
etc
etc
And you need them in both 1/4"’ and 3/8" drives. Sometimes, like when removing a corroded bumper bolt on a pickup, a 1/2" drive is nice. Oh, the torque you can create with a nice long breaker bar!
I chuckle every time I see an advertisement for “the only wrench you’ll ever need”.
the same mountainbike — ""line" wrenches (the box ends with the opening for a fuel or hydraulic line)">they are called flare nut wrenches, not line wrenches; at least get the terminology right
Both names are correct, actually. They’re also called tube wrenches. Or if you’re British, crow’s foot spanners.
The bung plug on my Toyota manual tranny was 24 mm and very prone to rounding off it the correct size BOX END wrench was not used.
Mechaniker, we use both where I’m from.
Crow’s feet where I’m from are the open end ends that you attach to the ratchet.
Nomatter, the point I was making is that there is no limited number of wrenches that will meet the needs of even the novice wrencher. At least not in my experience.
OP, btw, is also assuming that all of the nuts/bolts on the car are original. Maybe if you bought it new. Two of my three Japanese cars were bought used, and thanks to the interesting modifications on one made by previous owners I’ve found myself needing much more than his list. Including some SAE wrenches.
On my 4runner…the bolts to remove the caliper are 14mm.
I think there are a lot more sizes then just those mentioned in the first post.
Can’t tell you what cars they were but I remember needing standards and metrics to work on the same car. HASSLE!!
There’s no such thing as ever having enough tools to work on cars. Where i work we call them line wrenches. So does my Snap On guy. 16mm=5/8, 17.5mm=11/16. Try replacing the water pump on a Cadillac Northstar without the special socket, or a timing belt on a Honda. The list of special tools is endless.
Line wrench and flare nut wrench are both very commonly used names for the same tool, with line wrench being more common where I’m from. I also hear tube wrench from time to time. My father calls them flare nut wrenches, but the tool truck guys and my coworkers when I was an auto mechanic all called them line wrenches.
Regarding the use of common fastener sizes, I replaced a water pump for a friend this weekend on his mid '90s Dodge Ram conversion van with a 318 Magnum in it. Every single fastener I took off that engine was standard, and most were 1/2" or 9/16". The only metric hardware I had to remove for that job were two 10mm bolts holding the upper fan shroud to the radiator. Oddly enough, the two holding the upper shroud to the lower shroud were 7/16". I’m not sure what size the fan clutch nut was since I long ago got rid of my fan clutch wrench set, thinking I would never need them again. For this job, I just hit the flat of the nut with an air hammer to knock it loose. Worked out okay.