Starting May 1, drivers across the country will start seeing something a little different at the pump. The EPA has issued a waiver temporarily lifting seasonal restrictions on E15 gasoline, and if you fill up at your local station, you may want to know what you’re getting before you squeeze that handle.

E15 is a fuel blend that contains 15% ethanol and 85% gasoline. You’ve probably seen it at the pump already, marketed under names like Unleaded 88, Regular 88, or Clean 88. Normally, E15 is restricted during warmer months in many parts of the country because higher ethanol content can contribute to summer smog. But the EPA is rolling out this waiver to help ease pressure at the pump heading into the summer driving season, with the goal of lowering prices for American families.

The waiver runs from May 1 through May 20, though those dates could be extended.

So will it actually save you money? Possibly, yes. But there are some trade-offs worth knowing about before you pull up to the pump.

First, the good news. If you’re driving a car made after 2000, your vehicle can most likely handle E15 just fine. The majority of modern vehicles are built to run on it without any issues. Check your owner’s manual to be sure, but for most families carpooling to soccer practice or making the weekly grocery run, E15 is a reasonable option.

Now here’s where it gets important. The fuel does come with some downsides that matter to a lot of suburban households. Automotive expert Steve Haney points out that E15 can degrade faster than standard E10 fuel because of the higher ethanol content. If you don’t drive every day, or if you’re getting ready to store a vehicle for a stretch, filling up with E15 might not be your best call.

Haney also breaks down the fuel economy math. The average modern vehicle gets around 27 miles per gallon. Running on E15, you can expect roughly 26.5 MPG instead. That’s a drop of just under 2%. It’s not dramatic, but it’s real, and it can chip away at any savings you see at the pump.

The bigger concern for a lot of families in the suburbs is the small engine question. E15 should not be used in motorcycles, ATVs, boats, snowmobiles, generators, leaf blowers, chainsaws, or lawn mowers. We’re deep into spring now, and if you’re already pulling the lawn mower out of the garage on weekends, this matters. Small engines are especially vulnerable to ethanol damage, particularly when a piece of equipment sits for several weeks between uses.

Pre-2001 vehicles are also on the avoid list. The higher ethanol content can damage gaskets, cause fuel leaks, and create other mechanical headaches in older cars. If you’re driving a classic or keeping an older vehicle on the road, stick with standard E10.

Here’s a quick cheat sheet to keep in your head at the pump:

Your post-2000 car or truck is likely fine with E15. Your motorcycle, lawn mower, ATV, boat, or generator is not. Older flex-fuel vehicles can actually go all the way to E85, so check the label if you’re driving one of those.

Standard gasoline in the U.S. is E10, which contains 10% ethanol. Almost all gasoline already has some ethanol in it, so E15 isn’t a radical change. The extra 5% just comes with specific considerations depending on what you’re fueling up.

The bottom line for your family? If you drive a newer car and you’re watching the budget, E15 could offer a small break at the pump this spring and summer. Just make sure you know what’s in your garage before you default to the cheaper pump. A little savings on your commute isn’t worth a repair bill on your riding mower or your weekend ATV.

This is what being a smart local consumer looks like. Read the pump label, check your owner’s manual, and keep the small engines running on what they’re designed to handle.