With all the far north travels I have made in the far north, whether in a car or RV, remote roads or main roads, even locally, I always made the habit of carrying spare fuel no matter travelling within Alaska or Canada for various reasons.
Over the years since I first driven the Alaska Highway in 1985, it is
rare upon today's age that any given station at any one location will run out of fuel, but it can and does happen.
Noting the locations that do tend to run out of fuel supply at any given time are the more remote establishments and roadhouses, in comparison to the major towns.
As noted, the most vulnerable areas for a disruptive supply of fuel along the Alaska Highway should or when it happens is Northern BC and the Yukon Territory (cheaper priced fuel than Northern BC), as to my understanding the fuel supply is hauled in by truck via Alberta, as there are no 'fuel petro' refineries along Northern BC and the Yukon to my knowledge....I talked with two fuel haulers from Alberta while I was at Liard Hot Springs one day as they told me they make two runs to Dawson City every month during the summer.
In August 1991 when I passed thru Watson Lake in my 70 Thunderbird, there were many vehicles lined up at the gas pumps waiting for fuel to arrive as there was a disruption in fuel delivery for some reason, fortunate for me I was getting fuel at airports along the way as I could only run 100 octane fuel when I rebuilt the 429 engine in 1988 and kept it 11:1 high compression, as I was thinking I would have the potential availability problems getting that type of gas, and witnessed for myself seeing a major stop along the Alaska Highway temporary out of fuel, as I was the one on my way not delayed with a full tank and the 32 gallons of spare 100 octane fuel onhand for the longer stretches.
This was the only one time I have seen a 'major' town (or major stop) without immediate fuel availability upon my 17 one way trips from either direction along the entire Alaska Highway route, or a total of two times (Fort Simpson NWT the other place completely out of fuel) upon my 26 total crossings into Canada along other travels.
The more remote places within Canada or Alaska with fuel availability are the ones more subject to run out of fuel on short notice, or might close upon no notice or warning, so keep in mind not to always count on these places 100% for a fuel purchase, despite what the Milepost book shows for fuel stops as whatever edition one might have, the book certainly does not update itself.
Also, natural disasters, accidents, or infrastructure could come into play should another flood, extensive road closure, fuel tanker wrecks, major power failure, transmission grid post struck by lightning, generator failure (at remote places), refinery disasters, Alaska Pipeline shutdowns due to aging infrastructure, etc. ever happen to potentially slow, disrupt, or delay fuel delivery to many places along the Alaska Highway which is a lot of ground to cover.....in which all these scenarios listed above have happened in the past two years, however lucky enough with very little to no disruption in fuel supply which was the good news.
Another incident played out last year (Aug 2013) was when I pulled in to Border City Lodge 3 miles from the Canadian Border to top off my one tank before crossing into Canada (southbound), and finding out there was no fuel available with no warning in which they always sold fuel since 1989 when they opened for business, as the not so prepared northbound travelers got a rude awakening upon not carrying spare fuel thinking the place was still selling fuel while travelers bypassed purchasing fuel at Destruction Bay or Beaver Creek in order to save a few bucks (I can't blame them), while the rigs they were driving would not make it to Tok (90 miles away) with what fuel reserve they had left in their tank, relying on Border City Lodge for fuel.
My camper rig can carry 43 gallons of fuel (dual tanks) as I typically get mid to high 11 MPG range overall, however thru certain elements it significantly drops if the air is much thinner (low pressure), and if there is a lot of water grains in the air, and of course the favorite ol' driving thru the windy days and passes upon a headwind....I carry 10 gallons of spare fuel as I haven't had to use it while no emergency or disruptive fuel supplies came upon my way, the past 4 times I dispensed all my spare fuel in Fort Nelson (the most priced fuel in a 'major' town) before topping off my tank as I saved $12 to $19 depending in comparison of Fairbanks fuel price purchase of the spare fuel, which I will do when heading northbound as long as I hear of no word upon any incident heading towards the Watson Lake area where I plan to purchase upon my next fuel stop.
The one stretch I tend to keep a close eye for my rig more than any other area is the Whitehorse to Tok stretch upon most of the time I can easily make it without refueling in between, however when my altimeter gauge in Whitehorse reads over 3000ft. (as the true elevation is roughly 2200ft.) while it's raining, colder air, and windy at the same time, I will refill one of my empty gas cans in Whitehorse and carry 5 extra gallons for piece of mind, as I had to dispense the fuel only on one occasion in that situation (which I skipped Haines Junction, Destruction Bay, Beaver Creek and Border City Lodge fuel stations).
As others have noted, spare fuel along the Alaska Highway for most rigs is a non issue as I would say over 99 percent of the time there won't be an issue at all as everyone on this site had traveled extensively on it, however it is the far north and any of the examples I posted earlier that could go wrong might be a factor for fuel supply depending where one is at and if it plays out in any effect....I know these are the 'what if's' and all that, however if one's rig cannot conquer the greater distances between fuel stops compared to others, I would recommend carrying spare fuel a person feels comfortable with as I feel more confident carrying spare fuel in my travels in the far north, despite equipped with dual tanks - but that is just me.
It will be interesting to see how the majority of Alaska gets their supply of fuel as the largest fuel supplier at the North Pole refinery is closing and ceasing operations by June 1, as how it stands right now Alaska will be getting their fuel supply from Washington State, just another potential obstacle to face should a disruption in fuel supply occur, as the North Pole refinery tapping crude directly from the Alaska Pipeline will no longer be utilized.
The State of Alaska was attempting to negotiate keeping the refinery open while a prospect of new owners would takeover, however the latest news turned opposite direction as the state filed a lawsuit against the refinery for ground contamination against the current and former owners of the refinery, so look for higher fuel prices within Alaska as the best case scenario.
1975 Ford F250 2WD Ranger XLT (Owned June 2013)
460 V8- C6 Trans- 3.73:1 (196K Total Mi)
2000 Fleetwood Angler 8ft Cabover
Air Lift 1000 (Front)
Hellwig 3500 lb Helper Springs (rear)
Hellwig Front and Rear Sway Bars
Goodyear G971 LT Series (siped)