Cooley here with another one of your questions about high tech cars and modern driving.
This one's about the gas tank and what you put in it.
And how much.
Jacob L. in Pittsburgh says, I've been hearing from friends that putting more gas in your car after the first click of the pump can damage your vehicle over time.
Is it true?
Also, thanks again.
Because of your YouTube video review of the 2014 Mazda3, I actually bought one.
We love our Mazda3s, and the new one just came out, by the way.
I hope you saw those videos as well.
Now, let's get down to over filling your tank.
Or, is it over filling?
This is the question you're asking about.
Topping off is controversial stuff.
And, there are four reasons why I think people argue over it.
Four reasons that give me pause to not do it.
What we're talking about here is click, click, click, over and over.
After the first click when the pump says I'm full, many will tell you it's a waste of money if you keep pushing past the first click you could be overfilling at the top of your fuel fill port, and that just runs down the little drain there at the bottom of that port and to a tube underneath your car.
A lot of folks don't realize they're peeing gas on the ground and under their car.
Not a lot, but why throw that away?
Also on some pumps that fuel may be sucked back in to the nozzle that handles evaporative recovery hardware, taking it back into the tank.
So you're paying to give the gas station their own gas back.
It's not a ton of money, but why waste it, right?
The next concern, and the big one to me, is damage to your evaporative fume recovery system on your vehicle.
The evaporative recovery system has been in all U.S. destination cars since 1971 and what it does is make sure that the gas in the tank does not just evaporate fumes out into the air.
Those fumes have to be controlled and recovered in a system of tubes, valves, sensors, and this canister that charcoal in it.
That system can be damaged if it is forced to drink some liquid fuel, that an overfill could cause.
Now, not every car runs that risk Depending how the system's designed.
But why risk it?
If you **** that thing up, you're gonna get a check engine light, start failing emissions tests, and be facing a few hundred to a thousand dollar or so bill to repair it.
That's the one that keeps me awake the most.
Overfilling also has the potential to pollute the environment again a little bit.
But why do it all of that evaporative recovery stuff in your car and built into the fuel filler handle is meant to capture just about any Vapors and fumes that come off the fueling process.
But when you start over filling and splashing fuel around, or dumping it on the ground, you've defeated the purpose.
And the last thing to think about is a lot of folks use the first click as their benchmark for refill to do MPG measurements, because they don't trust the car's MPG gauge.
I can't tell you how many folks write into me and tell me, I don't trust that thing, I do my own numbers.
So they refill each time to the first click as they're standard benchmark and then compare the amount of fuel that dispensed versus the number of miles on the trip odometer.
But if you keep forcing fuel in there, I'm convinced you don't get a good benchmark of how much fuel you used since the last time.
So bottom line, be satisfied with the first click.
I don't think most cars get you a whole lot more range if you force feed them a whole lot more gas and run into all these potential issues.