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My old trusty Tahoe is a gas pig - how do I get better mileage?

I inherited my father's 1999 Chevy Tahoe in 2010. It has 223,000 kilometres on it. What modifications would save fuel on the 5.7L engine? – Joseph

There are a few things you could try, but the surest way to make a well-maintained Tahoe less thirsty is to change the way you drive it, an expert says.

"If fuel economy could be increased by adding snake oil or an intake turbine or what-have-you, manufacturers would have done it."says Eugene Eng, instructor at British Columbia Institute of Technology in Burnaby. "Look at all they put into R&D, lowering corporate average fuel economy and upping fuel economy to please consumers."

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The U.S. EPA rates the 1999 Tahoe at 16.8 litres/100 km combined. Changing that "is a tough ask," Eng says.

"The 350CI GM is a venerable workhorse, but it has never been known for economy," he says.

There are a few changes (to the vehicle and how it gets driven) that Eng says could improve fuel economy.

Get lower: Getting the SUV closer to the ground reduces drag and that could mean better fuel economy. But it's not a guarantee. And it's not a good idea if you'll be driving on rough roads. "Over the last few years, manufacturers have been lowering their vehicles to improve fuel economy and aerodynamics," Eng says.

Cut weight: "Don't carry more than you need," Eng says. "Whether it be cargo or vehicle accessories." That includes wheels and tires. Eng recommends sticking to the wheels and tire size recommended by the manufacturer.

Lose accessories: Add-ons like window vents and hood deflectors hurt fuel economy by disrupting airflow, Eng says. According to Consumer Reports, at highway speeds, more than 50 per cent of engine power goes to overcoming drag. And worse is unnecessary gear that makes an SUV look more rugged. It adds drag and weight.

"Does the soccer mom or dad need a bull bar?" Eng says. "Do they need more mounts for lights or protection from brush and foliage?"

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If you do get accessories, quality counts. "The ones sold or approved by the manufacturer are generally quieter, better fitting and less disruptive to the air envelope around the vehicle," Eng says.

Drive smoothly: "If fuel economy is a concern, minimize abrupt acceleration and braking," Eng says. "Fighting momentum consumes fuel." Slowing down saves gas too – drag increases the faster you go.

Drive while the engine is warm: Engines run more efficiently when they've had a chance to warm up. if you're making a bunch of short trips throughout the day and starting the engine from cold each time, you'll use more gas than if you combine those trips into one.

"Instead of going out on errands hours apart, make a grand errand tour," Eng says.

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