Myths about saving at the pump

With gas prices reaching record levels, everyone is looking for ways to save. Mass transit is one idea. But during the last big gas price hike, Times reporters checked out some ideas they'd heard about saving at the pump. Hector Becerra and Amanda Covarrubias found that some worked, others did not:

Myths and truths

Belief: Driving close behind a truck improves gas mileage because the truck cuts your wind resistance.

Reality: True, but it's also dangerous.

Belief: Gasoline stations near freeway exits charge higher prices.

Reality: Generally true.

Belief: You get more for your money if you fill up when it's cold because gasoline is denser at low temperatures.

Reality: Not really. Any difference would be insignificant and besides, most pumps correct for temperature.

Belief: Turning off the air conditioning saves gas.

Reality: True, but if you then roll down the windows, the increased wind resistance may eat up any savings.

Belief: Gas prices go up on the weekend, so fill up during the week.

Reality: Generally false.

-- Shelby Grad

Do you have any ideas? Share them here!

Comments

[Mike]

1) An electric air conditioning compressor will save gas and manufacturers are moving towards it, just like they are switching to electric power steering (either direct or electro-hydraulic) and electric water pumps. The reason why it is more efficient has to do with engine speeds. If a compressor connected to the engine directly is designed to provide enough pumping action at low engine speeds it will be a high power drain at high engine speeds. But designing for high engine speeds means inadequate pumping at low speeds. An electric system cuts out this RPM range and runs the compressor at only the ideal speed, eliminating the need for over-sized compressors.

2) Full throttle acceleration is THE MOST efficient way to accelerate. What is wasteful is HIGH-RATE acceleration. The two are different. The throttle controls air flow into the engine, as you close it the engine has to work harder to inhale air, resulting in higher pumping losses. High rate acceleration requires more additional power (and power=fuel). Full throttle acceleration at a slow rate is the best way to accelerate. Sadly Americans seem incapable of driving manual transmissions and an automatic treats the "gas" pedal as an accelerator pedal rather than a throttle pedal. When you give it a stab while in a high gear it will down shift rather than hold the high gear for better efficiency. A human can decide whether they want acceleration or efficiency at any given moment better than a car. Learn stick!

3) Displacement and number of cylinders are basically irrelevant. What is most likely to hurt mpg is power. A 300hp 2.0L 4 cylinder will be worse than a 200hp 3.5L 6 cylinder.

4) Gasoline storage tanks are underground and temperatures underground vary only slightly, a few degrees here and there. The difference is negligible compared to the amount that the pump could be mis-calibrated by. Check the Weights and Measures sticker on the pump to see when it was last checked.

5) Weight matters. Want a high mpg? Don't buy cars with 20 speaker stereos or whisper quiet interiors. Don't buy a 7 seater when you have a family of four. Don't get panoramic sunroofs or power seats. All that stuff adds weight.

[Dan]

It's not as simple as buying gas when it's cold to get the most fuel. It takes a long time for heat from the air to reach underground storage tanks. If this made any difference at all, I'd guess to fill up around mid morning to get the coolest fuel. It's easy enough to check with a thermometer.

[Robert]

"Many new cars have air conditioners that run on electricity (from the alternator) rather than from a fan belt. This is a very important feature in small cars, as the extra drag on the engine can really put a hurt on the mpg." - Figgins

It's not clear what your point is. Some hybrids have electric AC, no standard mass produced vehicles have it. Whether the energy comes via an alternator/generator or directly from the engine it still isn't magic: that energy first came from the gas tank. No free lunch, sorry.
In city driving there is a noticeable effect on mileage from using AC, BUT you are also going to be a better driver when you are comfortable. The smallest fender bender caused by fatigue from being hot will cost more than years of savings from going without AC in city traffic.

Sometimes it's borderline - if it's not humid or blazing hot you may be just as comfortable with the windows and sunroof open, and save a small but useful amount on fuel.

For highway driving in a car, which is more aerodynamic than a truck, you're better off using the AC.

The 5 "truths" quoted above are correct but a bit misleading.
#1. Full throttle acel does use more fuel, as the computer throws in more fuel to cool and protect the system. In some cases it also adds fuel after a sharp throttle motion - if you 'stab' at the pedal.
Engines are more efficent under a load, so it's actually converting fuel into motion better at, say, half power than by creeping up to speed slowly. That's why a 2 liter engine produces ten hp with less fuel than a 4 liter engine doing the same job - it's under a higher % load. It would be more accurate to say "drive smoothly; avoid full throttle and jerky aceleration". What wastes lots of gas is stabbing at the pedal, then hitting the brakes moments later. That's idiotic.
#2. In my experience, slowing down on the highway did help mpg but *not by much* - about 10% for cutting 15mph (this is with a passenger car). Driving *smoothly* helped more. On the highway you want to keep a near-constant speed and avoid braking, whether with the brakes themselves or engine braking. That forces you not to tailgate and squirrel around, which also reduces stress.

#5. This should be #1. Pooling 5 people in a Town Car makes it more economical than driving one's own Prius. There's no way to double, triple, or quadruple the gas mileage of the car you already own, but you can get 2-5 times the mileage per person by car pooling. That and cutting the number of miles you drive beat the most expensive, elaborate technology available. That Townie at 100mph with 5 people would _still_ beat the mileage of 5 Smarts w 1 person each blocking traffic at 55.

#6 A sun shade will also make the interior of your car last longer.

[Sealer]

Other readers are correct, retail fuel deliveries are not temperature compensated anywhere in the United States (although they are in Canada). That said, buying early in the morning does nothing to increase the amount of fuel you get. Underground storage tanks are dual walled and act as a buried thermos bottle, insulated from changes in temperature.

[Damon]

The avg density of gas around room temperature is about 6.5 lbs per gallon, so even if I drive with my 10-gallon tank half full, i'm only saving about 32 lbs in my 2800 pound civic (that's about 1.1% weight savings, might have a small but probably negligable impact on overall mpg).

[Raul Garcia]

Interesting such a horrendous misstatement implying gas pumps in California are temperature correcting was made; when in fact the oil companies are fighting tooth and nail to keep from having to implement them in California.

I'm moving out of California next month anyways...

[Eggbert]

1. Run red lights when possible... the longer you sit at the light, the more gas you are burning, when it could be used to get you where you are going.

2. Stop at bus stops and ask random people where they are going... if it's on your way... what the hell... you can usually get a few bucks out of those losers.

3. Shortcuts, shortcuts, shortcuts. I can't stress this one enough. Anytime you can dodge a street light(especially big intersections) when you know you're gonna stuck at, and won't be able to run it, look for shortcuts... like cutting through parking lots or neighborhoods. You can be as creative as you want with this one... especially if you have an off road vehicle. My personal favorite is making my own 'on-ramps' or 'off-ramps' to freeways.

4. Blow-up sex dolls are a must for commutes with car poll lanes... if you're one of those people who just hate other people... this is the way to go.

5. Put a huge electromagnet on your front bumper... when you're behind a semi, turn on the magnet, and stick yourself to the trailer... let that guy pull you along... he won't be able to see you... and to unhook, all you need to do is turn off the magnet.

[Rev. Dave]

Um.. err.. ride a bicycle? Or walk? Or ride public transit?

[Hal O'Brien]

Figgins: "BTW: where is the station in the photo? The prices are lower than near my place..."

The question isn't so much where, as when. It could easily be a file photo.

[Hal O'Brien]

Moving closer to your job so you can either walk or take public transit, and then selling your car or leaving it in the driveway for "emergencies," will save a *ton* of gas.

...and I speak as someone who lived in LA and didn't get his driver's license until he was 23. It was bus, bike, or walk for all those years. It's easily done.

[JayC]

It's refreshing to see pertinent, considered posts instead of flames and insults. Kudos to all of you.
As several have noted, easy launches save gas and use cruise control on the freeway.

[NV]

just a few more of these gas saving tips and we could reach 100% savings. Anybody up to the challenge ?

[Kathy Einwich]

I was around for the Arab Oil Embargo of 1973, and at that time there was a great deal of discussion of how to increase gas mileage. The consensus was that driving at any speed over 55 mph, gas consumption increased exponentially; thus for a time, remember, Interstate speeds were lowered from 70 mph to 55 or 60 mph (can't remember which). Also, of course, driving at city speeds, as can be seen in city-vs-highway speeds quoted for vehicles is much less. So: drive slower on Interstates at least (kind of a joke for LA perhaps?), save gas.

[Janet Woo]

Fill up your tank, not only will gas today will be cheaper than gas tomorrow...especially in LA...keeping only one or two gallons in your tank all the time will ruin your fuel pump costing you more than a tank full of gas.

[Figgins]

BTW: where is the station in the photo? The prices are lower than near my place...

[Figgins]

Many new cars have air conditioners that run on electricity (from the alternator) rather than from a fan belt. This is a very important feature in small cars, as the extra drag on the engine can really put a hurt on the mpg.

[james]

Don't circle a parking lot endlessly trying to find the closest spot possible. Head straight to the far end of the lot and park. You'll save gas and the walk will do you good.

Don't carry around heavy items in your trunk if you don't need to.

A friend of mine only fills his gas tank up half way. He says that the weight he saves by carrying less fuel around helps increase his mileage. The theory makes sense, but I've never tried it to see if it makes a difference.

[ToyotaTech]

Belief: You get more for your money if you fill up when it's cold because gasoline is denser at low temperatures.

Reality: Not really. Any difference would be insignificant and besides, most pumps correct for temperature.

Uh... You might want to recheck your facts...

According to your EMPLOYER (http://www.latimes.com/business/la-fi-hotfuel23-2008may23,0,7111171.story) California DOES NOT have temprature correcting pumps at even 5% of it's public gas stations.

Best bets are:
1. Check your tire air pressure every week and then use the VEHICLE manufacturer's decal on the left door post ( not the tire sidewall ) for the proper amount of air pressure. The tire sidewall only shows the MAXIMUM amount air allowed.

2. Drive with a lighter right foot.

3. Keeping the engine tuned and a clean air filter is a must.

Use common sense and save a few bucks...

Toyota Tech

[Jeremy R]

Truth1: Don't accelerate so hard will save you gas
Truth2: Driving slower on the freeway will have you gas
Truth3: Inflating your tires properly will save you gas
Truth4: Buying in bulk and combining trips will save you gas
Truth5: Carpooling to work will save you gas.
Truth6: In West LA, cracking your windows and putting up a sun shade will greatly eliminate the need to use AC

These are the 5 most effective truths that can easily cut your gas bill 30% (especially combining trips)

Forget wind resistance, the AC, trying to find gas stations that are 7 cents (1.5%) cheaper, etc.

If you would just think to stop at the grocery store and cleaners on your way back from a movie, instead of making 3 separate trips, you will save.

[Seth]

Myth Busters conducted an experiment to see which was more efficient: Windows down vs. air conditioning. The air conditioned truck ran out of fuel first.
Source:
http://kwc.org/mythbusters/2004/11/mythbusters_boom_lift_catapult.html