WELCOME TO CPF!!!
I'm not employed as a mechanic but find myself working on cars (mine and friends/family) quite frequently.
In my experience, for working on cars, a combination of approaches works best. As it turns out, the same combination is great outdoors while camping as well.
1. An efficient long lasting decently bright LED headlamp:
This keeps your hands free to work with tools as you are illuminating your work, or, for camping, makes setting up a tent or operating a camp-stove after dark MUCH easier.
Personal recommendation:
StreamLight Argo HP, find the version being sold described as having the "new C4 LED" as it's about twice as bright as the old Luxeon model and has even longer runtime. (more efficient LED). The Argo HP can run on either 2 CR123 primary cells, or alternatively, in the future, you may be interested in learning about the use of Li-Ion rechargeable cells, in which case this light will accept a single 3.7V 17670 size lithium-Ion.
2. A Hand-held lithium or li-ion powered incandescent.
Small enough to be pocketed in a LARGE pocket, or holstered reasonably well. I don't suggest bothering with the 2xCR123 size incandecents as they just aren't that impressive in my opinion (others may differ on this). My feeling is that this is the light you pull out when you need to OVERCOME sunlight or other strong overhead lighting to really spot something well under the hood of the car. A weak light here will not show up real well because your eyes are adjusted to the surrounding environment. In my experience, incans show up better when competing with other light sources, LED light gets washed out quite a bit. While camping a good strong incan with decent punch and throw will help throw down a serious beam off into the woods, gives a nice feeling of security being able to quickly identify whether that sound was a raccoon or a bear
Personal Suggestion(S):
Wolf-Eyes M90 if you want a lot of bang-for-buck and good rechargeable options and upgrades.
SureFire M4 if you think you will stick to CR123 primary cells and want a flashlight that is overbuilt and beautiful in every way.
The A2 that has been suggested would probably make do just fine, I just think you'll be happier with a more robust sized incan light.
Another point to make about 2xCR123 size incans, is they are quickly loosing ground to LEDs in this size. There are quite a few LED lights popping up now with 500-700 emitter lumens (300-500+ torch lumens) based on the new P7 LED that run on a single rechargeable 3.7V 18650 size cell, which is very close to the size of 2xCR123 cells. No incan in this size is going to overcome that kind of raw lumen output.
Eric