First, let me say I am not trying to drift this thread or turn it into another gas vs diesel debate. That said, regarding your tow vehicle
... here is another way to consider skinning that proverbial cat. Make a gasser vs diesel comparison. And don't be swayed by one side or the other. Be honest with yourself about it.
I'm estimating 95% of the forum posters are always going to advocate diesel. And for good reason. Diesels are in fact MUCH BETTER in every way. But at what cost? And is there value in that? Well, everyone's circumstance is different.
A truck has but one purpose. To tow or haul a load. If you're making the argument on MPGs of diesel vs gas while towing, well, you'll have to drive that diesel for a long, long time to validate your position.
I live and work overseas. But I am taking 6-9 months off work and taking my family on a long Western United States adventure. We needed a FW we could live in FT but also not one that I have to take a huge depreciation on since we'll likely store or sell it when we're done. So we went used in that category. We found a really nice 2005 model, immaculate, used bunkhouse FW with two ACs, a 10 gallon water heater, new awnings, and tons of storage. All for less than $10,000. Nearest retail priced version of this exact FW was $21,000. So we figured we could always get out of it for what we paid. We looked at new, and to be honest, we're still considering it, since the new ones have auto-awnings and auto-levelers (very expensive components) and comprehensive warranties. We then needed a tow rig. Of course, we started out looking for diesel since that's what I've always driven. But most of the used diesels needed work and the closer you get to new in terms of mileage or model year, the easier it becomes to just buy new instead. But at what cost?
Committing to a $55-65K new diesel truck wasn't fiscally prudent for our family, even though, thankfully, I now have the cash to pay for it. But I just don't want to take the financial hit when selling it. And storing a truck of that cost doesn't sound sensible either (storing once we complete our trip... assuming we don't sell it). If it was my everyday driver or I lived in The States again, I could see the justification. But not when I know I'll be headed back to the island we live on when our adventure is done.
So we started looking at used diesels. The problem with used is you don't know what maintenance and repair expenses are coming up. Most used diesels that are going for $20,000 already have 150,000 miles. Sure the diesel motor will last long. But all the other stuff will be needing replacement eventually, suspension components, vehicle accessories drive components (AC, oil pump, water pump, etc.). You could quite easily spend another $20,000 over the next few years, through no fault of your own. So now you're spending almost, if not more, than what a new diesel would've cost you, yet you'll never be able to sell it for even half what you have in it. Once you go sub-$15,000, you're looking at 200-300,000 mile diesels, sub $10,000 is the 300-350,000 mile market. Some of those will go another 2-300,000 miles but not all of them. Many will be needing a new engine or major engine/ tranny work. There are weak points in all diesels, all model years, it's just he way it is. Most of those weak points aren't revealed until well outside the warranty period. The weak points either expose the motors to damage (injectors on the 7.3 PS or 3rd gen CTDs) or leave you at the side of the road (TPS, VP44 or a myriad of other issues on my 2nd-gen CTD).
What I did, since I already have a fully-reconditioned diesel at my place overseas and didn't feel I could justify buying one just for a few RV trips, was go with a big block V10 gasser with low miles (107,000... yes, that's considered low these days
) and put a warranty on it for another $2400. The big block will greatly increase durability and I'm covered for any major repairs for the next 5 yrs/ 100,000K miles with the wty. It will cost me an average of $1043/ yr more in fuel to run the gasser (assuming 10,000 miles driven, which is the max we would tow with our schedule. And 8 mpg for the gasser vs 12 mpg for a diesel... towing). Note: I did not factor in the additional warranty cost because I would put a warranty on any diesel truck I bought as well. Those warranties are considerably higher so the equation would only get skewed in favor of gas anyway.
A 107,000 mile truck is equivalent to a 150-200,000 mile diesel, in my estimation, in terms of value-for-money. Sure the diesel lasts longer. But the gasser will be easier/ less costly to maintain. EX: If the engine blows on a diesel, $16,000, whereas on a gasser, $5,000. So I'd likely have to pay $12,000 MORE for a used diesel, vs a used gasser. $1043/ $12,000 = 11.5 years. IOW, I'd have to drive the diesel for 11.5 years to justify the added cost. Bear in mind, that does NOT factor in the much higher diesel maintenance costs, like oil changes, air and fuel filters, etc (roughly double the cost of gas). The above comparisons are for used diesels. The numbers are less skewed in favor of gas when buying new because the percentage markup for diesel is less due to the overall purchase price. So when buying NEW it makes better fiscal sense to go diesel both for better intended applications (the TQ advantage to tow heavier) and for resale value (you can ALWAYS sell a diesel for me, save for the dreaded Ford 6.0).
Were I you, I would put more money into your FW than your tow rig. Use the tow rig for it's intended purpose... to tow, and only (or mostly) for that purpose. Driving it far less than necessary will mitigate the mpg issue. But I would also buy a used VW TDI for getting around town, going to class, etc (TDIs get 40-50 mpg, depending on how you drive) or a similarly fuel effient vehicle. IOW, I would put the added $8,000 you mention (above the purchase price) towards a second (or 3rd) fuel efficient car and use it for errands/ work/ going to school. ONly drive the tow rig when hauling or once at the campground destination. But be sure to find a lower mileage gasser for the tow vehicle, if you chose this route, so that you can put a warranty on it and lock in your downside risk. That said, there is always the risk that the warranty company denies the claim. I get that. And some have warned me that warranties aren't worth the paper they're written on (I don't agree. I have had only positive experiences with warranty companies) But in case they're right, I factored that into my decision as well. First, the two biggest components of the vehicle, the engine and transmission: I can get a used engine for $1,000. I can get a brand new crated motor for $5,000, installed. I can get a rebuilt and upgraded transmission for $2000, with a warranty, installed.
That puts me back on the road, instead of letting some wty company dictate my life. Then I'll sue the warranty company for 3x the amount. I'm guessing a judge would rule in favor of a consumer were the case to get to court (assuming I had a legitimate claim) vs the a big warranty company.
Some people on here act as though diesel is THE ONLY option. It's not. And I say that as a diesel enthusiast. I am, for lack of a better term, a HARDCORE diesel fan. I have owned diesels for the better part of 20 years. I love the simplicity of the technology, yet the challenges it presents. But at the end of the day, I like financial independence much more, IOW, I don't like parting with my cash if I don't have to; and I don't like car payments. You can tow a 5er with a gasser no problem (a 3/4 ton or 1-ton gasser, I'm not a fan of half-ton towing because you don't have a robust driveline and you don't have the braking capacity). Some on here act as though it's impossible. Sure you may not be doing 70mph up a 7% grade, but you probably shouldn't be doing that anyway, even with the most stout diesel, while towing. Certainly the State Troopers/ CHP would have a problem with it. For stopping, drive slow in the hills, make sure your trailer brakes are robust, and replace the calipers on your tow rig. Basic common sense prevails. The average consumer towed with gas for years and years until diesels finally came into their over the last 10-15 years.
Now before the diesel crowd (which I remind you I'm one of) starts flaming me, let me state there is nothing wrong with buying a new diesel. In fact, I encourage it and I would absolutely LOVE to own an 2014 Dodge Ram myself... and I probably will in the not-too-distant future. But John, the OP, is on a budget. His money should be utilized towards his living space as long as he doesn't plan to put all that much annual mileage on the tow rig (I'm assuming he'll spend most time going to school or working). In our case, since we live overseas and only make a trip Stateside for RVing 3-4 times a year, we just couldn't justify the added expense of a diesel purchase, WHILE suffering the ensuing asset depreciation. Also bearing in mind, were we to finance it, a $55K truck really ends up costing $73,282 (assuming 100% financing at 3.9%, 8.75% sales tax and $600 for title and license). If life's plans change and you sell it 5 years from now for, say $30,000.... well, that's a huge hit. And that's not really the recipe for retirement planning. If you save $400/ month earning 10% a year starting at your age (I'm assuming you're around 25?), you'll have $4.4 million when you reach 65. If you wait until you're 35 to start that plan you'll only have $1.7 million. Only a 10 year delay in planning will cost you $2.7 million, or put another way, you'll MORE than double your retirement goal merely by starting 10 years earlier. Wait till you're in your 40s, and it's well below $1 million (more like $700,000). So the one thing you have working for you is AGE and the time value of money it brings. Use that to your advantage by avoiding bloated car payments, or buying more car than you really need, and instead fund a retirement plan. The day will come in when you'll be that guy driving the $2 million Prevost into the campground during your retirement years.
I knew all this information when I was 25, but I didn't listen. Now in my 40s, I'm having to save 5x that amount every month just to reach half that goal. The point? Be very careful when buying assets that depreciate aggressively after being driven off the lot. If you plan to own your diesel for 10+ years and plan to drive it a lot, then a diesel tow rig makes sense. The further you get away from those two requirements, the harder it is to make the case for diesel. If driving a gasser slows me down to 40 mph in the hills, so be it. It just means I get to the campgrounds an hour later.
The only limitation I see to buying a gasser is weight. Once we made up our mind on a gasser, that took a few of the 5er platorms out of the list. My goal was to find a FW with a GVW of 11,500 and an UVW of 8,500. I wanted 3,000 lbs for payload. And I wanted to be 2,000 lbs below GCVW for my rig, which mine is 13,400. I don't like pushing everything right to the max of it's limitation.
NOW... all that being said, if you're deadset on buying a diesel, here's what I would do. Spend $6-8,000 for a really high mileage 7.3L powerstroke F250/ 350 that has had the transmission recently replaced. I see these all the time on craigslist. Then take it to powerstrokehelp.com (Georgia) and get the engine totally rebuilt ($7,000). Now you're driving around a reliable diesel, with an upgraded motor. You're into it for $14,000 but you're way better off than the guy who bought a 200,000 mile PS for $14,000 cause you have a new motor and tranny. Believe it or not, even the venerable 7.3 PS breaks so while some motors will go 700,000-1 million miles. Most won't. Injectors need to be replaced, among other components and if that's not done, the motor gets compromised. The problem is pretty much everyone chips their rig these days. That means more heat. Heat kills these motors. Either way, if you go the diesel route, you'll need to invest a few weeks time on the forums of that model year and figure out the weak points. Then either find an original-owner truck or one that has already had those weak areas addressed.
When I bought my 5.9 CTD Dodge, I knew the VP44 was the weak link because I was on the forums. The previous owner swore he replaced it. He didn't, he lied. That cost me $2,000 (doing it myself), would've cost $5,000 at the dealer at the time. The vacuum pump went out, $3,000 at the dealer (I did it for $700). The power-steering pump went out, $1900 at the dealer (I did it for $400). Every PW and PL switch went out at least twice, clutch went twice (SouthBend warrantied the second clutch, but I still had to pay shipping overseas and labor). Radiator went out, water pump twice, starter once, etc, etc. You get the point. I have, what I believe, is the best motor out there but all the other components go out. Once you say diesel, it gets expensive to maintain. I knew this, being on the forums. But I tried my luck anyway. I still think I saved a ton of money buying a used low-mileage diesel. But it hasn't been cheap to maintain. I have owned this particular truck for 10 years.
When I bought the latest gasser, all those aforementioned experiences played into my thinking. I got in light so I can afford the occasional surprise. But I am under no illusion that gas is better than diesel. It's not. But right now, for my purpose, at this period in my life, it is by far the better financial decision. The only drawback in that I'll be in the slow lane through the hills, which makes little difference to me.
I have a home for sale in TX. When it sells I was planning on using some of the money to buy an RV lot in somewhere in Southern California and putting a FW on it and using it as our vacation home for whenever we travel Stateside (3-4 times a year). We plan to get a new toy hauler at that time so I will for sure be needing a diesel by then as the gassers just won't get much above 13,000 lbs. Accordingly, I can see the concise purpose in acquiring a diesel when getting into the heavier FWs.
Good luck with your search. There are deals out there, you just have to look hard, and know what you want/ need for the intended purpose.
Sorry... I know it's a long post. I got carried away in doling out advice.