Put $60-plus bucks in the tank and you can motor 774 miles in the U.S. before empty but a whopping 2,356 miles in Iran. Drive 1,000 miles in America and the fuel bill can top $90. And $50 of gas in Charlotte, North Carolina, will get you just out of the Carolinas or to northern Ohio, based on highest and lowest pump prices since the mid 2000s.

The wide gaps in figures show the numerous gauges in determining fuel economy, driving distance or price. It can vary by a vehicle's average miles per gallon, size of the tank and price of gas as well as how fast you drive, weather conditions and the type of terrain. The changes can show up most notably when driving through many countries say in Europe, Asia or Africa, or a host of U.S. states.

Veygo, a British car insurance company, developed what it calls a Global Fuel Price Index. The measure is based on 50 British pounds of "petrol," around $64 of gas by the latest exchange rates, filling up the tank in a Ford Fiesta — presently the United Kingdom's best selling car.

"When you fill up in the UK, you could drive for an average of 384 miles. In the U.S., this is 774 miles (double the distance)," according to Veygo. The highest totals are in oil-producing countries with lower fuel prices, such as the United Arab Emirates at just more than 970 miles and Egypt, 1,500 miles. On the low end are countries with soaring gas costs: in Norway, you would go 319 miles and Hong Kong, just 307 miles before stopping to fill up.

Visit https://www.veygo.com/global-fuel-price-index/.

In summer 2016, gas prices hit their lowest point in "recent history" at $2.18 a gallon, according to Business Insider online guide citing The New York Times. Christopher Woody, reporter for the business publication, penned an article then on fuel price variations. He highlighted figures from cost-information website How Much and SVM gas gift card company to show how far motorists can travel from major U.S. cities with $50 of fuel based on average gas prices in June 2005, 2008, 2011, 2014, 2015 and 2016 and a car that logs 24 miles a gallon.

According to the colored-coated graphics accompanying the story, you couldn't get past northern Virginia or Biddeport, Maine, from New York on $50 in 2008 but could cruise to Toledo, Ohio, or Fayetteville, North Carolina, on the same amount of money for fuel in 2005. A driver would have barely make it one state over from Denver a decade ago but would've reached El Paso or Kansas City for $50 three years earlier.

The web site Dollar Times offers a fuel calculator that computes the cost to drive 1,000 miles based on a few assumptions. A vehicle boasting 30 mpg and ringing up $2.75 per gallon would use 33 gallons of fuel costing $92 to travel that far, which would be the distance, say, from New York to Palm Coast, Florida. Go to https://www.dollartimes.com/road-trip/1000.   

This April, USA Today and Leaf Group, its "content partner providing general travel information," developed a primer on how to calculate gas mileage for a trip.

Writing for the national newspaper, Lisa Maloney of Leaf Group quipped, "Nothing says 'carefree' like the great American road trip — until you run out of gas or find yourself waiting tables to pay for that next tank of fuel."

She says the math isn't so hard. In fact, "almost every modern vehicle has an onboard computer that will calculate your gas mileage for you; just toggle to that part of the display, reset the computer, then drive normally for at least half a tank of gas." At the next fill up, note how much gas it took to fill up and add up the miles driven. Then divide the driving miles by gallons. "For example, if you drove 200 miles on 8 gallons of gas, your car averaged 25 miles per gallon," Maloney says.

On vacations, map out daily routes and use an online mapping system "to tote up the mileage for your trip" and divide by the vehicle's average miles per gallon to roughly determine the amount of gas to buy.

"You can use tools like Gas Buddy to estimate your gas cost in a given part of the country, but even then, make sure you add in at least a 10 percent fudge factor to include things like wrong turns, detours, sudden surges in gas prices, or decreases in fuel efficiency from sitting in traffic jams," she says.

Maloney also points out that drives through rural areas can rack up long distances between gas stations, so "it's always a good idea to hedge your bets by carrying a small can of extra gas."