Ok, you don't NEED it, but believe me, it's the one thing that will make the whole game MUCH more comfortable
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biggest advantage - the trunk (as any other container) offers unlimited storage room for any type of ammo (except BB) and travels with you
Actually, the trunk doesn't offer unlimited storage. I'll admit, you can fit an unimaginable lot of stuff in there, but at some point it is completely full. At least that's what happened to me a few times, before I installed Killap's Restoration Project.
@ homer: Yes, refuel it with Microfusion Cells. If you picked up the part for the car in Klamath the car will get better mileage so it will cost you less Cells to fill her up, it'll be 50% for 50 Cells (one ammo case).