If you maintain the cars well, eventually the roadside tool kit will get smaller and smaller, because you know you've addressed the critical maintenance items one by one.

I used to carry my tool box in my trunk, with all my basic tools (it's not much) and a few filters, belts, jumper cables, etc. Now I leave the toolbox behind but carry the multi-tool, a set of main and pre-filters, fuel return lines I've never needed to use, spare lug bolts, and the jumper cables. Funny thing is I've never had to use them at all, but may prove useful if I need them for somebody else, which has happened a few times when I needed to boost their batteries or lend them an adjustable wrench for clogged filters.

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