Aren Jay
09-08-2008, 09:04 AM
Truths and myths about how to save on gas
By Steven Cole Smith, Orlando Sentinel Automotive Editor
FICTION: Use a do-it-yourself fuel additive We've heard of everything from acetone to mothballs to WD-40 being added to the gas, and though some users claim a modest increase in mileage, the additives can cost more than any gas savings can justify. Plus, good luck in getting manufacturers to honor any warranty claims if they learn you have been using unauthorized additives.
FICTION: Choose a manual transmission Not always, but usually -- probably four out of five times, the manual ekes out a slight mileage advantage. The real advantage of the manual is that it can cost as much as $1,200 less than the automatic.
FACT: Know your numbers To improve mileage, you have to know what your current miles-per-gallon usage is. Simply computing how many miles you get to a tank is too imprecise. First, find out what sort of mileage you should be getting. Go to fueleconomy.gov -- the Environmental Protection Agency has recalculated mileage on cars back to 1985.
FICTION: Buy gas only in the morning The theory is that when it's cool, the gas is more concentrated than when it's hot, and you get more for your money. But this is unlikely. Gas comes from in-ground storage tanks, and their temperature doesn't vary much. Plus, modern gas pumps compensate for any discrepancy. Still, if it makes you feel better . . .
FACT: Add it up The best way to compute mileage accurately is to fill your tank at your favorite gas station, at the same pump every time. As the tank nears full, set the nozzle to flow on the lowest setting, using the little clip that most pumps have that allows you to keep your hand off the nozzle. When the tank is full, the pump turns off. Pick a set round-trip route to this gas station. Then refill the tank and see how much gas you used. Divide the amount of gas you used into the number of miles you drove.
FICTION: Install a fuel-saving device Probably not. Popular Mechanics tested a variety of them, from vortex generators and water injectors to magnets, ionizers and atomizers, and not one worked. Some, the magazine warned, could actually come apart and damage the engine.
FACT: Plan, plan, plan Assume you have three possible routes to work -- two requiring stop-and-go driving, the other expressway or parkway driving. Which is the cheapest? The only real way to know is to drive all three, check your mileage and see whether the gas savings outweigh the extra distance and the tolls. If your vehicle is getting the EPA-suggested overall mileage, then you can probably make an educated guess that the around-town route would get you an average of the EPA's city mileage, and the expressway or parkway roads would get you the EPA's highway mileage.
Of course, that's assuming you have Ez-Pass -- if you have to idle at toll booths while you toss in quarters, you are partly turning your highway drive into a stop-and-go city route.
FACT: If you're not in the ballpark, get help Poor mileage? A savvy mechanic will make sure the engine isn't idling too fast, the ignition timing is properly set and the thermostat is keeping the temperature within the optimum range.
FICTION: Drive with the tailgate down Not true, especially on modern pickups, which are aerodynamically designed to allow air to flow over the empty bed rather than into it, causing drag. We asked Matt O'Leary, chief engineer on the 2009 Ford F-150. He said the truck's roof redesign helps flow the air over the bed, and a spoiler on top of the tailgate helps.
FICTION: Let the engine idle This was more true back in the days of carburetors and nonelectronic ignition, but it isn't true now. At idle, you get zero miles per gallon. If you expect to idle for more than two minutes, turn the engine off.
FACT: Slow down Yes, driving more slowly does use less gas, and we can prove it. Using a test car that has a trip computer -- a 2008 Saab 9-3 TurboX sedan with a six-speed automatic transmission and a 280-horsepower V-6 engine -- we conducted a few tests. First, we drove a 10-mile stretch of open road, with no stoplights or stop signs, at 55 to 60 mph, then 65 to 70 mph. Average mileage at 55 to 60 mph: 26.4 mpg; at 65 to 70 mph: 24.9 mpg. Of course, your mileage may vary, but repeating this test three times, we got within 0.2 mpg with each run.
FICTION: Get a locking gas cap Not true on newer vehicles. Since the 1980s, the vast majority of vehicles have anti-siphon baffles that prevent a hose from extending down into the tank. On older vehicles, you probably want a locking cap.
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By Steven Cole Smith, Orlando Sentinel Automotive Editor
FICTION: Use a do-it-yourself fuel additive We've heard of everything from acetone to mothballs to WD-40 being added to the gas, and though some users claim a modest increase in mileage, the additives can cost more than any gas savings can justify. Plus, good luck in getting manufacturers to honor any warranty claims if they learn you have been using unauthorized additives.
FICTION: Choose a manual transmission Not always, but usually -- probably four out of five times, the manual ekes out a slight mileage advantage. The real advantage of the manual is that it can cost as much as $1,200 less than the automatic.
FACT: Know your numbers To improve mileage, you have to know what your current miles-per-gallon usage is. Simply computing how many miles you get to a tank is too imprecise. First, find out what sort of mileage you should be getting. Go to fueleconomy.gov -- the Environmental Protection Agency has recalculated mileage on cars back to 1985.
FICTION: Buy gas only in the morning The theory is that when it's cool, the gas is more concentrated than when it's hot, and you get more for your money. But this is unlikely. Gas comes from in-ground storage tanks, and their temperature doesn't vary much. Plus, modern gas pumps compensate for any discrepancy. Still, if it makes you feel better . . .
FACT: Add it up The best way to compute mileage accurately is to fill your tank at your favorite gas station, at the same pump every time. As the tank nears full, set the nozzle to flow on the lowest setting, using the little clip that most pumps have that allows you to keep your hand off the nozzle. When the tank is full, the pump turns off. Pick a set round-trip route to this gas station. Then refill the tank and see how much gas you used. Divide the amount of gas you used into the number of miles you drove.
FICTION: Install a fuel-saving device Probably not. Popular Mechanics tested a variety of them, from vortex generators and water injectors to magnets, ionizers and atomizers, and not one worked. Some, the magazine warned, could actually come apart and damage the engine.
FACT: Plan, plan, plan Assume you have three possible routes to work -- two requiring stop-and-go driving, the other expressway or parkway driving. Which is the cheapest? The only real way to know is to drive all three, check your mileage and see whether the gas savings outweigh the extra distance and the tolls. If your vehicle is getting the EPA-suggested overall mileage, then you can probably make an educated guess that the around-town route would get you an average of the EPA's city mileage, and the expressway or parkway roads would get you the EPA's highway mileage.
Of course, that's assuming you have Ez-Pass -- if you have to idle at toll booths while you toss in quarters, you are partly turning your highway drive into a stop-and-go city route.
FACT: If you're not in the ballpark, get help Poor mileage? A savvy mechanic will make sure the engine isn't idling too fast, the ignition timing is properly set and the thermostat is keeping the temperature within the optimum range.
FICTION: Drive with the tailgate down Not true, especially on modern pickups, which are aerodynamically designed to allow air to flow over the empty bed rather than into it, causing drag. We asked Matt O'Leary, chief engineer on the 2009 Ford F-150. He said the truck's roof redesign helps flow the air over the bed, and a spoiler on top of the tailgate helps.
FICTION: Let the engine idle This was more true back in the days of carburetors and nonelectronic ignition, but it isn't true now. At idle, you get zero miles per gallon. If you expect to idle for more than two minutes, turn the engine off.
FACT: Slow down Yes, driving more slowly does use less gas, and we can prove it. Using a test car that has a trip computer -- a 2008 Saab 9-3 TurboX sedan with a six-speed automatic transmission and a 280-horsepower V-6 engine -- we conducted a few tests. First, we drove a 10-mile stretch of open road, with no stoplights or stop signs, at 55 to 60 mph, then 65 to 70 mph. Average mileage at 55 to 60 mph: 26.4 mpg; at 65 to 70 mph: 24.9 mpg. Of course, your mileage may vary, but repeating this test three times, we got within 0.2 mpg with each run.
FICTION: Get a locking gas cap Not true on newer vehicles. Since the 1980s, the vast majority of vehicles have anti-siphon baffles that prevent a hose from extending down into the tank. On older vehicles, you probably want a locking cap.
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