It has always bothered me that South Africans take such an interest in topping off their petrol tanks when fueling. Some have elevated it into a kind of sport. I once watched a man bouncing up and down on his bumper in an effort to slosh the fuel around in his tank and squeeze a bit more in. I’m convinced that petrol attendants have some fancy mathematical formula they use when topping off to get the amount due to a suitably un-rounded number that will maximize their tip when customers say, “keep the change.”
The loser in this game is the air we breathe. Petrol vapours are carcinogenic, and, given a little time and sunshine, they create smog. Overfilled fuel tanks are likely to leak, especially if parked in the sun. Topping off greatly increases the likelihood of a spill, and even a minor spill is bad news. Just a shot-glass (30 ml) of spilled petrol gives off the same volume of smog-forming VOCs (Volatile Organic Compounds) that a car emits when driving 90 kilometres.
The issue is so serious that in the U.S., nearly every fuel pump you see at filling stations has a “Don’t Top Off” sign on it. Some U.S. States even sponsored a “Don’t Top Off” week, to get the message across. The U.S. Environmental Protection Agency has a whole web page devoted to the subject.
It’s a lot easier to do the right thing if you know it has some direct impact on your wallet, so these campaigns also emphasize that overfilling means paying for petrol your car might never use. Yesterday I read another reason that continuing to add fuel to a tank after the pump has automatically shut off could cost you money. The New York Times ran an article about the tricks some car-owners have used to keep their vehicles going after 200 000, 300 000, and even 400 000 miles. (These are miles, not kilometres.) The Times offered this advice from Toronto mechanic Vladimir Samarin, who has a car-care Web site at www.samarins.com.
Mr. Samarin also warned drivers not to overfill their fuel tanks. “Otherwise you could get fuel into the vapor canister,” he said. If that happens, the charcoal in the canister could find its way into the fuel lines and cause damage. “When you get that first click of the gas pump, stop refueling.”
Of course it would be nice if the government or the petrol retailers could take the lead in this issue. As far as I can tell, they have done nothing. Until they do, tell your petrol-station attendant that his tip will be bigger if he stops at the click.