Gas Saving Reality Check

by Eric Peters
EricPetersAutos.com

Everyone’s jumping on the “how to save gas” bandwagon – understandably. It’s on everyone’s mind. But that doesn’t mean you ought to believe everything you read.

For instance, there’s the bogus:

Regular tune-ups will save you gas

Most late model cars (that’s anything built over about the past ten years or so) generally don’t need regular tune-ups. Spark plugs last as long as 100,000 miles; ignition systems are largely maintenance-free and the car’s onboard computer automatically adjusts things like the air-fuel ratio and ignition timing to optimize performance and economy. Unless the “check engine” light comes on, or you notice a change in the way the engine sounds/performs (or your mileage suddenly decreases) you should not worry about tune-ups until the time/mileage interval specified in your vehicle owner’s manual.

Until then, just change the oil and air filter (when needed) and keep the tires inflated. That’s usually all you need to worry about.

Warm up your car before you drive off

In the days when cars were fed fuel by carburetors (and took several minutes to reach normal operating temperature) this was a good rule to follow. But cars haven’t come with carbs since the late 1980s – a quarter century ago – and a modern car reaches normal operating temperature within moments of start-up. Idling the engine for several minutes actually wastes fuel because it takes longer for the engine to warm up – and (among other things) reduces the efficiency of the catalytic converters, which take longer to “light off” (reach the temperature necessary for them to efficiently process the exhaust) which in turn reduces operating efficiency – and thus, increases fuel consumption as well as emissions output.

The right thing to do is to get in, start the car – and drive it.

Using lower-cost “regular” gas saves money

This is only true if your vehicle was designed to burn regular unleaded. If, however, you own a vehicle designed to run on high-octane premium fuel, filling up with regular is a bad idea because your engine’s efficiency will be reduced – and you’ll probably end up getting worse gas mileage, as well as reduced performance. The engine’s computer will dial back ignition timing and other parameters to compensate for the lower octane fuel, which means it will not be operating at peal efficiency – which means, you end up using more gas. The kicker is, you also get dialed-back performance.

It’s just as counterproductive, on the flip side, to burn premium gas in an engine built to run on regular. You won’t get more performance – and you may see a mileage loss – as well as the loss you’ll pay up front for buying the higher-cost premium fuel.

To maximize the fuel economy potential of any engine, use the type of fuel it was designed to burn – whether that fuel is 87 octane regular or 93 octane premium.

Fuel saving gadgets

Whether poured in or bolted on, the “miracle mileage boosters” you see advertised on TV or online have (so far) invariably been shown to be bogus. Think about it: If the car companies could up the fuel economy of their cars by 5 or 10 MPG (or even 2 or 3 MPG) simply by adding a $10 magnet to the fuel line or a “vortex” to the air intake, why would they not install the thing at the factory? They’d meet their CAFE compliance targets (or get closer) at little to no cost and without having to re-invent the wheel. But they don’t – and that ought to tell you something.

Then there’s the legit:

Get the garbage out of your trunk

The more weight you’re hauling, the more gas you’ll be using. Only carry with you what you need to carry with you. Don’t use your trunk or pick-up bed for long-term storage. You might even consider removing the full-size spare (if your car came with one) and carrying a couple of cans of Fix-a-Flat instead. If you have a pick-up, you can probably remove the tailgate and shed 50 pounds or so (which is what will save you gas, not improved airflow).

Switch to synthetic lubricants

Not just engine oil but also manual transmission and axle lube. Synthetics have better flow characteristics at extreme temperatures of cold and hot, which reduces friction, which increases fuel efficiency (as well as performance) and also reduces wear. The difference in smoothness/operating characteristics, synthetic-equipped vs. not, is especially noticeable in very cold weather. The math also works out more favorably when we’re talking manual transmission/axle lubes – which typically only need to be done once every 30,000 miles or so (and maybe much longer than that) vs. engine oil changes, which usually need to be done once every 6,000 miles or so.

Finally, the maybes:

Shut off your engine if you expect to be idling for more than 30 seconds or so

Hybrids save gas by shutting down the gas side of the gas-electric powertrain when the car comes to a stop. You can do the same thing without all the high-tech assistance of a computer – or the expense of buying a new Prius. Shutting off the engine when you find yourself stuck in traffic or hit a really long red light can reduce your overall fuel consumption by as much as 5 percent. Just be aware that you may also reduce the life of your starter motor – and you’re working your car’s battery harder than you otherwise would, which could mean it dies sooner than it otherwise would have.

Don’t run your AC; roll down your windows instead

This is a “maybe yes, maybe no” fuel saving suggestion. Older vehicles – generally, those built prior to the mid-1980s – had AC systems that were very power hungry, with huge compressors that took a lot of energy to drive them. If you’ve driven such a car, you may recall actually feeling the load on the engine when the AC was turned on. If you have one of these old cars, you can indeed save some gas by limiting the use of your AC. But with modern cars, the potential fuel savings are lower because the AC systems in modern cars are much more efficient. They don’t load the engine nearly as much – and you might actually end up burning more fuel by rolling down the windows and increasing the car’s aerodynamic drag. Rule of thumb: If your car is a 1990 model or newer, running the AC probably won’t increase your fuel consumption much – if it’s even noticeable at all.

Keep your car washed and waxed

Some people believe a clean car drives better than a dirty one – and they may be on to something. A smooth, clean surface cuts through the wind more efficiently than a bumpy lumpy one. Increased wind resistance means higher fuel bills – though the increase is probably very small, for the most part. With one exception: If you have a truck or SUV and have taken it off-roading, caked-on mud clinging to the undercarriage and fenderwells can add a surprising amount of weight to the vehicle – as well as increase drag. A session with a power washer can get your fuel bills back to where they ought to be.

Reprinted with permission from EricPetersAutos.com.

October 28, 2011

Copyright © 2011 Eric Peters

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