Comments on: Can You Improve Gas Mileage By Filling Your Tank Half-Way?

By: Dianne

Dianne — Thu, 07 Aug 2008 22:59:33 +0000

I have a question, I have been aruguing with my cousin’s husband about gas mileage and how you should not put in 5.00-10.00 at a time to go here in there in a 1985 GMC Suburban., instead of putting in all of it at once to put more gas in like 30-40 dollars, which gives about 1/4 tank in my suburban. He says its less weight. But my truck weighs enough already and I believe that you need to put atleast 1/2 tank in it to get the best gas mileage. Can You Help Respond by email. Thank you

Dianne

By: Morgan

Morgan — Thu, 24 Jul 2008 22:18:01 +0000

Perhaps a better timing strategy for buying gas is to wait till the price drops below some moving average then buying as much as the car will hold. This is what I try to do (on a gut estimate rather than a calculation of the moving average.) It works better with the freedom of timing afforded by low consumption.

As for the optimal speed for AC, the rate of heat exchange through the radiator will also be improved at higher speeds. I just always roll the window down out of habit, except the window motor is now failing. (I just got the steering repaired, so the car trying to reestablish its equilibrium level of non-functionality.)

By: jv

jv — Thu, 24 Jul 2008 01:25:00 +0000

I mostly agree with everything, especially the conclusions. In addition though to stopping for gas more often (and extra starts and miles to get the gas station) you also lose some probably trivial amount through evaporation and vapor. I don’t know if the recovery systems they added a few years ago actually recover it or just keep it out of the air.

But add another easy thing to do to increase milage:

Properly inflating your tires. And of course, biking or walking or carpooling.

jv <– foofy prius driver.

By: Stephen

Stephen — Wed, 23 Jul 2008 16:24:41 +0000

Three cheers for foofy! With luck, we can soon spread that adjective throughout the internet.

By: Stephanie Files

Stephanie Files — Wed, 23 Jul 2008 15:47:27 +0000

I’ve decided that you must be a member of the Mythbusters staff. They did at least one episode on gas mileage and efficiency. They attempted to prove that driving with your windows up actually eliminates drag and saves gas. They too concluded that it was an inconsequential difference in the grand scheme of driving, therefore I enjoy my hot summer drives with the AC on. I will also add that I’m going to enjoy acting like a 2 year old by inserting FOOFY into every possible sentence for a while.

By: Stephen

Stephen — Wed, 23 Jul 2008 14:53:42 +0000

Paul, this is my skeptical face. 4%? Really? It’s the equivalent of removing several hundred pounds from your car? Washing and waxing your car will improve your aerodynamic profile, but not by that much.

In doing a little digging, I see the EPA’s site on fuel economy estimates 2.6% of your car’s energy goes to overcoming aerodynamic drag. That number will fluctuate depending on how fast you’re driving, but I can’t imagine it going much above 4 or 5%, in which case they’re claiming that washing and waxing your car will completely remove the effects of drag. So, no, I’ll add this tip to the pile that includes “put magnets on your fuel line!” and “overinflate your tires!”

By: Seth Vidal

Seth Vidal — Wed, 23 Jul 2008 14:36:26 +0000

My grandfather who is 86 this year suggested that if people really wanted to save gas and reduce waste then we’d lobby for a return to a much older speed limit standard.

45mph max on the highways.
35mph max on any non-highway road.

We’ve gotten so wedded to the “fast and right away” I wonder if people can ever conceive of a less-so being acceptable.

By: Paul O'Brian

Paul O'Brian — Wed, 23 Jul 2008 13:58:56 +0000

A claim I saw in the movie theater last weekend: washing your car leads to a 4% mileage improvement. I can’t quite figure that one out. Is the dirt adding drag? Must I wax to reduce friction?

By: Anna

Anna — Wed, 23 Jul 2008 12:48:09 +0000

I’ve wondered about the whole filling the gas tank only halfway thing. It’s interesting to think about the numbers of it.

And I think “foofy” is my new favorite adjective.

By: Geof F. Morris

Geof F. Morris — Wed, 23 Jul 2008 09:55:04 +0000

I’ve seen analyses that argue that removing, say, 100 lbs of junk from the car [:whistles innocently:] would get you 3-5%. Yeah, it’s not gonna get you very much.

[You mentioned SSTO because you knew I was going to read this. I don't know whether to be appreciative or to shake my fist in your general direction.]