Running out of fuel in the middle of nowhere is one of the few overlanding mistakes that can turn a great trip into a genuine emergency. Unlike a flat tire or a dead battery, there is no quick roadside fix when your tank hits empty 80 miles from the nearest station. The question every overlander eventually faces is simple: how much fuel should you actually carry? The answer depends on your vehicle, your route, and how much margin you want for the unexpected. This guide walks you through the math so you can plan your range with confidence instead of guesswork.
Start With Your Real-World Fuel Economy
The fuel economy printed on your window sticker is nearly useless for overlanding. Loaded down with gear, water, recovery equipment, and a rooftop tent, then crawling through sand, mud, or rock at low speed in low range, your consumption can easily double. A truck that returns 22 mpg on the highway might drop to 10-12 mpg on a hard trail.
Don't guess. Track your actual economy across a few trips that resemble the terrain you plan to tackle. Fill up, reset your trip meter, drive your typical mix of trail and dirt road, then divide miles driven by gallons used at the next fill. Do this on graded forest roads and again on technical terrain so you have a high and low figure. Plan your range around the worst-case number, not the average. The difference between 12 mpg and 18 mpg over a 300-mile leg is roughly eight gallons, which is the gap between making it and walking.
Calculate Your Range and Add a Safety Margin
Once you know your real economy, the basic math is straightforward. Multiply your usable tank capacity by your worst-case mpg to get your baseline range. A 26-gallon tank at 11 mpg gives you roughly 286 miles. But you should never plan to use the full tank. Treat the bottom quarter as a reserve you only dip into in a true emergency.
A practical rule of thumb is the one-third rule borrowed from boating and aviation: one third to reach your destination, one third to return, and one third held in reserve. For a there-and-back trail run, this means your turnaround point should be no farther than one third of your total range. If your route is a loop or point-to-point with a known fuel stop, plan to arrive with at least a quarter tank to absorb detours, getting lost, idling for winching, and running accessories.
Always research fuel station locations along your route before you leave, and assume at least one will be closed, out of fuel, or simply gone. Remote stations are notoriously unreliable. The station that was open last season may not be open this one.
How Much Extra Fuel to Pack in Cans
When your route exceeds your tank's safe range, jerry cans bridge the gap. The standard NATO-style fuel can holds 20 liters, or about 5.3 gallons, which adds roughly 55-65 miles of range on the trail for a typical mid-size to full-size rig. To figure out how many cans you need, subtract your safe tank range from your total route distance, then divide the remaining miles by the range one can provides, and round up.
For most weekend trips into moderately remote country, two 20-liter cans of extra fuel is a sensible baseline. For multi-day expeditions deep into the backcountry, three or four cans is not unreasonable. Be honest about diminishing returns, though: fuel is heavy at about 6.3 pounds per gallon, and every can you add hurts your economy and your payload. There is a point where carrying more fuel costs you more range than it provides.
Quality matters more than people expect. Cheap plastic cans crack, leak fumes, and degrade in UV exposure. Steel cans like the Wavian jerry cans are sealed, pressure-tested, and built to military specification so they won't vent fuel vapor into your cargo area or fail on a rough trail. A leaking can is both a fire hazard and a slow loss of the very fuel you are relying on.
Store and Carry Fuel Safely
Where and how you carry fuel matters as much as how much. Mount cans externally whenever possible, on a rear swing-out carrier, bed rack, or roof rack, rather than inside the cabin where fumes can accumulate. Always carry fuel cans upright and secured with proper mounts or ratchet straps so they cannot shift, tip, or chafe against sharp edges over washboard roads.
Keep a quality flexible spout or pour nozzle with your cans so you can transfer fuel cleanly without spilling it down the side of your vehicle. Inspect seals and gaskets before every trip, and never store ethanol-blended fuel in cans for more than a few months, as it absorbs moisture and degrades. Label diesel and gasoline cans clearly if you run more than one vehicle in a group, because a single wrong fill can sideline a truck for the rest of the trip.
The Practical Takeaway
Plan your fuel around three numbers: your worst-case trail mpg, your safe tank range using only three quarters of capacity, and the total distance between reliable fuel stops. If the gap between your safe range and the distance to the next pump is larger than zero, fill it with quality steel cans and add a margin on top. For most overlanders, knowing your real economy and carrying two solid 20-liter cans covers the vast majority of trips. Build that habit, verify your numbers on every trip, and you will never have to find out how far you can push an empty tank. Browse our selection of military-grade Wavian fuel cans to carry the extra range you need safely.