He's right, unless you study up on making biodiesel. Then you have the upper hand in the argument, as a diesel Jeep can be run on biodiesel. Rendering those fatty zombie corpses to fuel should be a functional disposal method.
That and after a while gasoline expires even in the tank of a car. After like a few months he would have to be making his own fuel anyway, because whatever gets siphoned can't be used.
Not a terrible play, but it has a BIG downside you might not be considering.
99.99% of the corn grown first world, and a lot of other food crops, are sterile hybrid varieties that don’t readily reseed themselves (Monsanto and company HATE when farmers don’t have to buy seed every year).
Once there is no more harvesting or maintenance on stockpile equipment, that supply will dwindle faster than you might expect.
Fuck corn. It is patently one of the worst feedstocks for ethanol. The only reason you hear so much of it is because there is so much money wrapped up in it already and it is a way to use up excess stock. No, switchgrass is the answer. Hearty, more biomass per km² than just about any other crop, has high cellulose content (which is what gets turned into ethanol), and can be cultivated just about anywhere on the continent with little maintenance or involvement. You could probably get away with planting a few fields in pockets around a stronghold which could be checked on a couple of times a week and harvested for an extended period, then you just have to process it as usual. It is even relatively short and dense, so zombies would struggle to hide in it and it would act as a natural barrier to slow the advance of both Zs and any nairdowells that would seek to assault you. Fuel source and defensive emplacement in one.
I'm swapping the first-aid kit for the crossbow, but spot on for the rest. Body armor is rare and definitely raises your odds of survival in the short term after the initial spread. A machete is the ultimate all-purpose blade, good for defense as well as butchering, breeching, and it is easily maintained. And the water purifier is a no-brainer. Waterborn diseases are a real problem in any situation where public utilities become inaccessible and clean drinking water grows scarce.
Assuming that I am obviously able to expand my kit as I survive, the ranged weapon that uses easily craftable ammo would be ideal. A first aid kit could be cobbled together over the course of a few days of persistent scavenging. No promises on the crossbow, they are far less common than bandaids, gauze, sterilization solutions, and splints. Really the thing that would likely be the hardest to source is the suture needle that you should have in there.
I always loved 10k in Z-Nation for using the wrist rocket slingshot because that is truly the king ranged weapon for a survival scenario. Lightweight, ammo that is infinite and easily accessible, and lethal out to ranges that matter. Not to mention that they are very easy to maintain and repair.
All that said, I would likely accumulate the aforementioned electricity/fuel items as I am familiar with the production of biofuels and can build some alternative generators (wind, methane, solar concentrators) for electricity once I have somewhere secure. Methane in particular has always been attractive to me for survival scenarios because anaerobic decomposition is a great way of dealing with biowaste and what is left over ends up making really good fertilizer. Just need a couple of propane tanks, some steel, and a car battery to rig as a welder and you can turn one into a digestor and the other into storage, then get a couple 2 cycle lawnmower engines and some AC motors and you can get a power supply running. At least enough to run some incandescent bulbs. Need a voltage regulator for more complex electronics to keep the line clean, but that is a different conversation.
Also, as I said, for usability and reliability in efficacy and ammo sourcing, nothing beats a wrist rocket slingshot. The weapon itself is lightweight and can use everything from ball bearings and buck shot to large bolts and nuts to gravel. There is virtually no terrestrial environment that you wouldn't be able to find something that can be used as absolutely lethal ammo.
They only have to be serviceable, which is manageable just like they were made in from antiquity to the modern era, wood. It might take some practice, but a hand-carved shaft that has the tip dipped into molten lead or pewter could make a rather effective bolt. You could use more modern materials as well; various types of piping, scavenged hardware like nails and dowels, etc. They may be less accurate and harder on the crossbow, but they don't need the longest range in this topic and the wear and tear on the crossbow may be justified if you know how to repair it and maintain it to ward off failure. Obviously, there would be trial and error, but it wouldn't take too long to become a competent Fletcher.
I don't have a PhD in zombiology but zombies will bite you wherever they can. Depending on what kind of zombies we're talking about a bite alone might turn you or not. So body armor could be useful for some kinds of zombies and utterly useless for others.
It's good for general protection too. It can soften blows from other humans or just accidental injury while scavenging dilapidated buildings. What we consider to be minor bumps and scrapes now can be life threatening when you have inadequate medical supplies, malnutrition, sleep deprived, no sanitation, etc.