Recent Comments:
Kelley Blue Book studies gas-savings habits and announces top fuel-efficient picks {Autoblog Green}
Jun 21st 2007 4:53PM There was a recent study from either Consumer Reports or Edmunds that said dirty air filters don't reduce mileage on modern cars with airflow sensors; the computer picks up the reduced air flow, and compensates by reducing the flow of gasoline to the injectors. What you do see is a drop in power and acceleration, but that's not necessarily a bad thing.
Care to try making your car a "Homemade Hybrid" with the ten second rule? {Autoblog Green}
Mar 29th 2007 1:12PM I do that as well, but use 30 seconds as my criterion. The break-even point for modern fuel-injected cars is 10 seconds; for older cars with carburetors, it's longer than that, but probably not 3 minutes. The Canadian government says that shutting down you engine when you'll be standing still for 30 seconds or more adds about $7 a year for the average car in increased maintenance costs because of the increased wear and tear on the starter, but you save far more than that in fuel costs alone.
20 percent of UK driving on under-inflated tires {Autoblog Green}
Mar 13th 2007 1:48PM In 2001, NHTSA did a study of tire pressure in the US, and the results were pretty bad as well:
- 27 percent of passenger cars had at least one tire considered to be "seriously underinflated", i.e. a warm tire with a pressure 8 psi below the manufacturer's recommended cold tire pressure.
- 13% had at least two tires that low.
- The numbers were even worse for SUVs, pickups, and vans. 33% had at least one tire seriously underinflated, while 20% had at least two tires in that category.
- While 85% of drivers claimed they were concerned about maintaining correct tire pressure, only 36% took an active role in monitoring their tire pressure on a regular basis (weekly or monthly). 25% only checked their tires "when they seemed low"; 28% only had their tires checked when they brought their cars in for service
- A median vehicle (at the 50th-percentile) had all four tires underinflated by a combined total of close to 10 psi, meaning roughly a 1% drop in fuel efficiency (this means that half the vehicles on the road are even worse)
- Only 25% knew where to find the correct cold tire pressure for their cars
And the pressure numbers are even worse than they appear at first glance, since they were measured at gas stations when the tires were hot (increasing their pressure by 4-5 psi), and the tire pressure specified by manufacturers is the cold pressure.
The EPA says you lose about 0.4% in MPG for every 4 psi in combined underpressure for all four tires.
Full Speed Tests - How fast can you go? {Download Squad}
Feb 23rd 2007 10:59AM I'll stick with speedtest.net; not only is it free, and won't try to sell you anything, but the interface is fun.
Nitrogen vending inflation station set to save you fuel {Autoblog Green}
Feb 14th 2007 12:54PM I second these comments. I haven't found a single technical study to back up the claims of improved mileage from using nitrogen, and I've looked. All the reports are anecdotal, and promoted by the makers of nitrogen-filling equipment.
It's said that you can lose about 1 psi per month by leakage through rubber (though I don't see nearly as much). Oxygen leaks through rubber about 4 time faster than nitrogen, but there's about 4 times as much nitrogen as oxygen in air, so the oxygen loss is responsible for at most 0.5 psi of loss per month. Switching to all nitrogen would cut your monthly drop to a bit more than 0.5 psi, a trivial amount. You should be checking and filling your tires monthly anyway, for the reasons cited in the second comment (though I don't buy the argument about water condensation being a factor).
Love your wallet: eleven fuel saving tips to put money back in your pocket {Autoblog Green}
Feb 14th 2007 12:46PM 2. Too light a touch on the throttle can sometimes waste gas. Accelerating from a full stop, the usual advice is to do it slowly, as if you have an egg between your foot and the gas pedal. But studies have shown it's more efficient to depress your pedal about two-thirds when accelerating from a stop, shifting to a more-efficient higher gear as quickly as possible.
4. Tire pressure is important, but more for safety than fuel economy. The oft-quoted figure of "1% drop in MPG for every 2 psi a single tire is underinflated" is wrong. The EPA now says that you lose about 0.5% in MPG for every 1 psi all four tires are underinflated. This is consistent with Consumer Reports and Edmund's findings that grossly underinflated tires (25% less than the recommended values) only cut mileage by about 1 MPG.
5. According to DOT studies, peak MPG occurs at around 55-60 MPH, but MPG is fairly flat from around 30 MPH to 60 MPH.
8. Consumer Reports looked at the effect of clogged air filters not that long ago, and found no difference in MPG between clean and clogged filters. The reason, they discovered, was that the car's computer compensated for the reduced air intake by reducing the amount of gas it fed to the engine. So MPG stayed the same, but performance suffered - acceleration wasn't as good. This is in contrast to the claim that a clogged air filter can cost you up to 10% in fuel efficiency.
Can we solve global warming by giving everyone free Gas-X? {Autoblog Green}
Feb 12th 2007 7:08PM Uh, Tim, maybe you should refrain from posting if you don't know what you're talking about. The warming in question took place during the Paleocene-Eocene interval in the Cenozoic, not the Jurassic, which was about 40 million years earlier. Scientists in fact have a pretty good idea what caused it - a massive release of methane hydrates from the ocean floor:
http://www.nsf.gov/od/lpa/news/03/tip030512.htm#second
And they also have a pretty good idea of what's responsible for the commencement of the most recent set of ice ages about 40 million years ago, the creation of a permanent ice sheet in the Antarctic as continental drift moved it south towards the pole, and the resulting change in global weather patterns.
Rohrbacher isn't being sarcastic, he's being either dishonest or willfully ignorant.
Can we solve global warming by giving everyone free Gas-X? {Autoblog Green}
Feb 12th 2007 1:37PM Maybe someone could point out to this notorious looney that dinosaurs died out 65 million years ago ...
"I pledge allegiance to getting better mileage" {Autoblog Green}
Jan 18th 2007 2:50PM Phil,
My source is West, McGill et al., "Development and Verification of Light-Duty Modal Emissions and Fuel Consumption Values for Traffic Models", 1997 FHWA report. Averaging over 9 different car models (8 from the 1990s), they found that the average MPG peaked at about 55 mph. Even for the worst class, large SUVs and trucks, MPG peaked at about 45 mph. Comparable data for early 1980s models showed a peak in MPG in the 35-45 mph range; it's likely that improvements in aerodynamics and tire rolling resistance, along with engine design, were responsible for much of that improvement.
I seriously doubt that many in India takes those "motorized rickshaws" up to 50 mph. And even for 1970s vintage vehicles, whose MPG peaked at about 30 mph, MPG was only down about 15% or so at 55 mph compared to 30 mph.
"I pledge allegiance to getting better mileage" {Autoblog Green}
Jan 18th 2007 11:40AM Good idea, educating kids at an early age. But it would help if they got their facts right. Driving at 50 mph does not use 50% more fuel than driving at 30 mph; mileage actually peaks in the 50-60 mph range, though it's not that much higher than what you get at 30 mph.
