[QUOTE=GoForAGallop;8061823]
No, but there are many other costs to consider.
Particularly since OP is considering new, you need to factor in an extra $5k (on average), up front, for the diesel engine. It takes a long, long time of once a month trips for an extra $60 in fuel to balance out that initial $5k.
Because of that upfront cost, they also then cost more to insure. (And taxes!) Purchase price aside, diesels are also usually more expensive to insure in general.
Diesel mechanics (good ones!) can be hard to find in certain areas, and when they know they’re good, they charge a premium. OP’s mechanic may be a great one, and is just charging what she feels are higher prices simply because he can. It is not as difficult to find maintenance for a gas engine.
Diesels also like to be worked, they do best with regular use. OP says this is not a daily driver.
It’s definitely not a black or white choice, that’s for sure. 
Lots of things to consider when you’re counting up costs, more than just the current 50 cents difference per gallon.
I grew up towing with a big diesel Chevy Suburban. I tow with the aforementioned giant gas truck now because it just fiscally made more sense. With even used diesels being at a premium (thanks to them being a status symbol in my hick town :rolleyes:), it just made more sense, for me, to go with the big gas engine, since it’s not a regularly driven vehicle.[/QUOTE]
It might vary with different insurance companies. My 2009 GMC Duramax was the same price to insure as my 2003 Yukon Denali. No difference… We are able to insure with USAA, though, so we often get prices others cannot get. But I can’t see the price being that different with any other company.
I also don’t pay taxes on any vehicle purchase because I am an Alaska resident and tag all my vehicles in Alaska. Tags are cheap - $100 for 2 years for every vehicle DH & I own (4 total). They all have vanity plates on them. I think Wyoming may also be tax free??? Or I could well be mistaken!
For a few years, my GMC was a daily driver. But other than that, every diesel we have owned since 1999 has pretty much only moved if towing something weighing over 10K, and generally averages 5K miles a year. Or less. Have yet to have a mechanical issue, other than DH burning up the transmission on the '99 Dodge in 2001 with his lead foot, even when loaded. I know there are lots of RV folks out there that rarely use their diesels (think of all the snowbirds with diesel pusher RV’s) and don’t have significant problems. I used to believe the “diesels need to be worked” adage, but I’ve become less and less of a believer over the years.
So it really doesn’t struggle on inclines, although you have some bigger mountains than I do! Any chance you have a friend with a big gas truck that you can take for a spin, even if it’s not brand new?