Your mechanic wants you to stop doing this at the gas pump, today.

When I'm going on a long-distance trip, the first thing I do is I get out the minivan, make sure the tire pressures are correct and then I fill it up. When I get to the gas station, I do something that you're probably doing too, and I just found out I should not be doing it, and if I keep doing it, it's going to cost me a lot of money. 

What I'm talking about is topping off the tank. I pull up to the pump. I select the grade of gasoline and put the nozzle in and start pumping. Then when the pump shuts off, the next thing I do is try to put more gas in. I try to get it as full as it'll go. I just found out this is not something you should be doing. 

Have you ever heard of an EVAP or fuel evaporative system? Well, guess what? Every car has one, and yours does too. And if you keep filling your car up the way I do, you're going to ruin it. And then you got to buy a new one, (EVAP that is) and it ain't cheap.  

according to dailydot.com,
“the consequences can be severe, ranging from damaged purge valves to potential engine damage. This issue is not isolated to the Explorer but extends across the automotive spectrum. The urge to “top off” the tank can lead to significant financial and mechanical headaches.” 

My first reaction is to say, hey, look, it's the gas tank. It's supposed to hold gas. I find it difficult to believe that there is such a thing as overfilling a gas tank. Well, guess what there is. 

According to autotrader.com,
“Attempting to cram that “little bit extra” can compromise the evaporative emission control system, designed to prevent gasoline vapors from polluting the atmosphere. Overwhelm this system with liquid fuel, and you’re looking at costly repairs.” 

And it's true, you could wind up spending up to 600 bucks replacing that EVAP Gizmo. Plus, I don't want to get my minivan worked on right now. My favorite mechanic just retired. (Mike, I miss you buddy) 

So, don't overfill your car. I'm going to try not to. I hope you try not to as well. It'll save you money. It'll help the environment a little bit. And you're still gonna get to where you're going on time, no problems. 

Mechanic Warns: Don't Overfill Your Gas Tank Over This Happens (dailydot.com) 

What Is an EVAP Leak And How Do You Diagnose It? | The Drive 

Car Mechanics Urge Us to Stop Doing This at the Gas Pump Now (popcrush.com)