For most Americans, Memorial Day is a holiday with two faces. First and foremost, it is a solemn remembrance of Americans who have lost their lives while serving in the armed forces. So there can be a disconnect between the holiday’s core meaning— which is especially important to those of us who have served in uniform– and this weekend’s unofficial role as the kickoff for summer vacations.

But there is one thing that connects both sides of the holiday: oil. Over-reliance on oil ties our nation to far-flung conflicts, sends our troops into harm’s way, and endangers them once they’re in conflict zones. And oil will power tens of millions of family road trips over the next few months, with AAA predicting a potentially record-breaking summer driving season as gas prices are lower than in the recent past.

Historically, cheaper prices at the pump have led consumers and policymakers alike to put gas savings and efficiency on the back burner. But it’s critical for our country to keep pressing ahead with reducing our oil dependence. That’s especially true given this year’s government review of fuel economy standards. Ensuring that the cars and trucks we drive every day go farther on every gallon of gas makes our nation stronger.

{mosads}When oil prices are high, exporting countries in the Middle East and Africa, and others like Russia and Venezuela can use oil as an economic weapon, exploiting other  oil dependence to coerce and to extract concessions. Now that oil prices are low, those same countries are fighting one another for market share. They see their oil revenue falling, and that makes their internal politics less stable.

That’s just one reason why CNA’s Military Advisory Board, on which I serve, has found that reducing America’s overreliance on oil is a national security priority. The more removed our own economy is from the messy geopolitics of oil, the safer and more independent we are, and the more flexible we can be in our responses to international crises.

Oil use affects our military on the battlefield level, as well. As the U.S. commander in Iraq’s Al-Anbar Province a decade ago, I witnessed the aftermath of enemy attacks on slow-moving fuel convoys. Improvised explosive devices and enemy snipers took a terrible toll. I saw first-hand that cutting down on the military’s use of oil would reduce the number of dangerous fuel convoys, and save American lives.

As America’s single largest user of fuel, the Department of Defense is doing its part to move away from oil. Consider the service in which I served, the Marine Corps, which is working to cut the amount of fuel consumed per Marine per day by 50 percent, and to obtain half of the energy used to power installations from alternative sources by 2020, while Marines in the field use tactical solar panels that allow them to turn off generators and reduce fuel convoys. Across the armed services, since 2009, conservation and alternative-energy efforts have saved the Department of Defense an estimated $1.2 billion in energy costs.

The United States as a whole is also making dramatic progress in reducing its oil consumption. The largest step we’ve taken on this front is setting fuel efficiency targets that ensure vehicles get more miles per gallon. Over the past several years, advances in automotive technology have virtually eliminated many “gas guzzlers,” even as automakers sell more pickups and SUVs that get better gas mileage than ever before.

This is great progress, and the United States must continue to build on it. Fuel economy standards were born amid the Arab Oil Embargo of the 1970s and have been tightened a few times since then. If federal agencies and automakers stay the course through a forthcoming round of even higher fuel economy standards, the average vehicle will achieve 40 miles per gallon in real-world, on-road performance by 2025. By 2030, that would reduce America’s oil use by more than three million barrels per day— an amount roughly equivalent to our oil imports from the Persian Gulf and Venezuela combined.

The age of over-dependence on oil is winding down, and not just in the United States. When even Saudi Arabia announces major plans to move its economy away from reliance on oil, you know the world is changing.

Here at home — especially for veterans and those who have lost family members who were serving their country — Memorial Day’s status as a day to remember fallen Americans will never change. And, I suspect, neither will the day’s unofficial role as summer’s kickoff. But whether on highways at home or on battlefields abroad, we can help our country by using less oil, and change our energy future. An America less reliant on oil is a stronger, more secure, more independent nation — the kind those we remember fought for, and the kind we celebrate.

Lt. Gen. Zilmer retired from the U.S. Marine Corps in 2011 after 36 years of service. He is a member of CNA’s Military Advisory Board, an elite group of retired generals and admirals that studies pressing issues to assess their impact on national security.