St Albert Dodge Newsletter

This Fall’s Chrysler Promotions — Save a Few Bucks!

Come on in to St Albert Dodge today to find out more about our New Fall Promotions!

Comments Leave a Comment
Categories News Items

Fuel-Saving Tips!

6 Driving Tactics to Save Gas! (Courtesy Popular Mechanics)

Tactic No. 1: Coast to a Stop

Brakes are necessary (duh!), but they’re inherently wasteful: They take the kinetic energy of a moving car—energy it took pricey gasoline to generate—and turn it into heat that’s lost to the air. Everyone knows that accelerating until the last moment then braking hard to stop is less efficient than slowly coasting to a red light. But PM’s test data (illustrated below) prove what a huge difference coasting makes. The lesson: Whenever possible, anticipate that a light will turn red and ease off the gas. Generally, the less you have to brake, the better your fuel economy.

Tactic No. 2: Avoid Slowly Crawling Up to Speed

Conventional wisdom says that jackrabbit starts consume more fuel. But it turns out that nursing your speed up to the limit too slowly also lowers mpg. How can that be? Cars get poorer fuel economy in lower gears, and accelerating too slowly prevents upshifting at an efficient rate. The best acceleration rate varies with the vehicle, gear ratios and weight. But in our testing we found that taking 15 seconds to accelerate to 50 mph used less fuel than taking 30 seconds to reach the same speed, because the car entered its top, fuel-saving gear sooner.

Tactic No. 3: Close Windows and Use a/c at High Speeds

It’s a fierce efficiency debate: Open the windows in summer to avoid running your energy-intensive air conditioner, or keep the windows closed and the a/c on to preserve your car’s aerodynamic profile. (We’ll leave aside the option of sweating it out.) PM’s testing settled the issue. Driving at 55 mph with the a/c running, we got 24 mpg; turning it off bumped us up to 28 mpg. Then we opened all four windows, one at a time, and lost 1 mpg per window until we were back at 24 mpg. So at that speed, it’s a wash. But aerodynamic drag rises exponentially with speed—the faster you go, the more the open windows hurt efficiency. The answer? Below 55 mph, open the windows and leave the a/c off. But at 60 mph or higher, keeping them closed and the air conditioning running will burn less fuel.

Tactic No. 4: Cruise at a Slower Speed

Since the power required to overcome aerodynamic drag is a function of the velocity cubed (in other words, it shoots up quickly), a car’s jump from 40 to 60 mph requires less fuel than the increase from 60 to 80 mph. (As the graph above shows, the hit to fuel efficiency is roughly twice as severe in the higher range.) So go slower, right? Well, yeah, but fuel efficiency isn’t the only thing that matters. Some studies suggest that the old 55-mph limit saved fuel but cost us more in terms of lost work hours. Then there’s safety: Going 55 mph when traffic is cruising at 70 can be dangerous to everyone. Just don’t go 80. That will drain your tank quickly—and the costs add up if you also have to pay for a speeding ticket.

Tactic No. 5: Climb Slowly (When It’s Safe)

Imagine driving on a flat highway and approaching an overpass. From a fuel-efficiency standpoint, the best strategy is to turn off cruise control and forget about maintaining a constant speed up and down both sides of the grade. The theory predicts that, and our data prove it. The physics work like this: Lifting off the accelerator while traveling up the hill and allowing your speed to decay trades some kinetic energy (related to speed) for potential energy (related to the car’s tendency to roll downhill). You regain the kinetic energy—and get better gas mileage—on the backside. While hypermilers—who are obsessed with getting the best possible gas mileage—claim significant economy benefits from this technique, our results showed only modest gains. Two things did happen, though: (1) We drew the wrath of a lot of drivers following us, as evidenced by their single-finger salutes; (2) We were nearly sideswiped by an impatient 18-wheeler. Yes, the method does work. But we’ll save it for lightly traveled roads.

Tactic No. 6: When Coasting Downhill, Leave the Car in Gear

There are those who refuse to be shaken from the practice of coasting downhill in neutral to save gas. This is a bad idea no matter how you look at it. Let’s set aside fuel economy for a moment. Coasting downhill in neutral is illegal in most states. And it’s dangerous in all states. In neutral, you have no way to accelerate to avoid a hazard, and if the engine stalls, you have no power steering or vacuum boost for the brakes. If the hill is steep enough to call for hitting the brakes to keep you from gaining speed, they’re more likely to overheat—and overheated brakes lose effectiveness until they cool off. They’ll probably do that right around the time the police show up to take the accident report.

Here’s the surprise: There’s no tradeoff between safety and fuel economy in this case. Leaving the car in gear while coasting downhill actually is more efficient. Why?

Most fuel-injected engines today use computer-controlled Deceleration Fuel Cut Off: When you lift your foot from the gas while leaving the car in gear, injectors shut off automatically, and the car’s rotating tires—which are connected to the engine via the transmission—keep the engine turning and the accessories running. So, the engine consumes no fuel at all while the vehicle is coasting downhill.

In contrast, the fuel-consumption rate for an engine idling in neutral falls between 0.2 and 0.4 gallons per hour (gph). Splitting the difference and using 0.3 gph for our example, idling in neutral down a ½-mile-long hill consumes fuel for 30 seconds, for a total of about 0.32 ounces of gas. Popping the car into neutral actually wastes gas.

This may seem counterintuitive, but that’s what data are for—replacing good guesses with solid facts. Watch the data, and over time the savings will take care of itself.