Got an RV or a Travel Trailer? If so, you've got a Survival Vehicle. Pretty obvious why; if you can drive your rig to some remote location and have comfort on some level and ability to choose your site, you have many potentials.
Many though spend lots of bucks readying a 4x4 SUV or Truck with every upgrade and modification. As if once collapse occurs, they expect to be out driving around. Of course, America is/was an "on the go" society, but just as the zombies in Dawn Of The Dead came to the mall because "it's what they know from life", investing a lotta $$ in a survival vehicle that won't accommodate your living in it might be a Big Mistake.
Many would-be survivalists fantasize about the Bug-Out Run. They remain tied to a city lifestyle, job and home etc; but are readying gear and a place to head to when they decide to Bug-Out of Dodge. Yet, unless you have someone living at your BOL (bug-out location), you could find others already there... The handwriting is on the wall. Don't think that there aren't bad-guys scouring the countryside looking for gear to loot or unoccupied dwellings off the beaten path which they can squat at.
Sadly, most who plan a BOR (bug-out run) are likely to be too late in making their effort. Once it is obvious to everyone that they also need to get outta Dodge, there will be pandemonium or a travel lock-down. If residing at your BOL is key to your plans, you best be there NOW; or at least have your family and gear relocated. You might get as much as a one hour leadtime to put your BOP (bug-out plan) into motion. Is that realistic? Probably not.
Those who've invested mucho dinero in a tricked-out vehicle hopefully have tended to all their other needs before blowing lotsa money on a truck or SUV. Not gonna be a lot of driving for pleasure or for reconnoiter. The roads will be watched by all. Not too realistic to expect a roadtrip to be like a Sunday outing. Maybe you gotta make a trip to a doctor or hospital in life threatening situation, or to flee the advance of a hostile army or armored column, but unless you own a large ranch or farm, not gonna be much driving done.
Storing gasoline? Not a great idea unless you've got an underground tank. Diesel stores very safely, but not gasoline. If you want to keep some fuel restoration fluids, PRI-G, and PRI-D are worth considering. G for gasoline, D for diesel. Cost about $25 to treat 250gals. Highly regarded. For more recent gasoline that may have lost its octane, I have found Acetone works very well. I use a few drops for old fuel remaining in chainsaws or other small engines. 2.5oz per 10gal is supposed to optimize burn rates in autos both diesel and gasoline motors.
Plenty of cool 4x4 vehicles out there if you want to spend the money. Newer vehicles though have many computer controls and complexities that make them a questionable choice. I have owned turbo-charged Powerstroke Ford and Cummins Dodge and consider the 12v Dodge to be the most reliable and durable motor you can own.
Need traction to get into the outback but no money for a 4x4? As long as your wheelwells will allow enough clearance to use chains, not cables, you are in luck. Chains will get you almost anywhere as long as you don't stick your axle or swamp-out in deep water. 4x4 is not very useful in those circumstances either. If you have a front-wheel drive, the chains go up front.
As for bugging-out, most cities of any size these days have freeway or highway loops that surround them. If you live outside the Loop, you are more likely to have some odds of making your getaway. Freeway and highway loops are effectively barriers which can be held with a relatively small force and serve to contain the population within. When/if Martial Law is declared, likely the Loops will already be locked-down or will be in quick-time. The hour you think you have to set your move in motion might be way optimistic...
Not much reason to tie-up a lot of money in vehicle(s) unless you've tended to all your other needs first. If you need a truck, the Dodge Cummins from `95 to `98 offer the superb 12v motor and shift on-fly 4x4; plus minimal computer controls. Probably find one for about $5k in good shape. Probably worth rebuilding and these get 20+ mpg with a load. Not much reason to spend $50k for a new equivalent, especially if your not going to be driving much in the future anyway...
As far as the vehicles you do own, being ready means keeping it topped up with fuel, new coolant and oil, recent trans service and current on all lube service, plus a new or recent battery. Probably want to keep a set of belts, coolant hoses and have brake pads/discs looked at. Brake fluid does absorb water over time, and if trailering a load, your brakes must function 100%. Good idea to drain/bleed your brake lines and be sure all is optimal.
If figuring to make a BOR, know several alternate routes and drive your route every few weeks to be sure no surprises await you like sewer or waterline replacement that means major street construction and ditches that could be obstacles. Also want to have a CB Radio in your vehicle and give a listen routinely just to see what the truckers might be discussing. Family radios or SSB (single side-band) CB could be very useful while in transit. Might consider 10m ham transceivers or even marine band transceivers for on the road use on a limited basis. Obscure channels so you attract minimal attention. Might even have a mic-key code so you aren't transmitting voice in the open.
Very likely that once things begin to look dicey, anyone leaving the city with a load of gear could be a target for looters. Another good reason you want to be 10 days too early rather than 10 minutes too late...