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Fuel Economy on Diesel Engines
In the late '70s and early to mid-'80s you probably remember there were quite a few cars with diesel engines. GM tried the diesel engine option in Oldsmobile Cutlasses and full-size Oldsmobiles; Cadillac had diesel engines, even in some of their front-wheel-drive cars - and there was even a Chevette diesel. Mercedes made lots of diesel engine cars. And one of the main ideas of putting the diesel engine in these vehicles was they were, in many cases - leave out the Chevette - but in most cases they were heavy, non-aerodynamic cars that gave pretty poor fuel mileage with a gasoline engine. So by substituting a diesel, they improved the fuel economy and it appealed to many people.
But in terms of today's cars, you've got mid-sized cars getting thirty-five to thirty-eight miles per gallon; you've got compacts and sub-compacts getting forty-five to fifty miles per gallon and better in some cases. So, the push for getting a diesel engine is just not there anymore. The advantages are not as clear cut.
One of the very few cars that you'll see on the showroom today with a diesel engine is the Volkswagen with the TDI - or turbo direct injection - engine. I've driven those cars. The performance is pretty good. The driveability is good and the fuel mileage is great. But the feedback that I get from my customers that own them and from other motorists I talk to on the street is that, when it comes to repair time, in some cases they're kind of wishing that they hadn't opted for the diesel engine because repairs on any diesel engine are considerably more expensive than a gas engine.
However, there is one market segment where we really need to talk about the diesel engine option and that's the light trucks. Pickups, vans, sport utilities, cube vans. In most cases, all of these vehicles have at least one diesel engine option. In a half-tonne chassis, in most cases you're better off with just a gas engine.
In other words, if your truck needs are what we term light-duty, a half-tonne chassis'll do, gas engine is probably your best bet. When you get into three-quarter and one-tonne chassis and certainly into cube vans or anything that's used for towing a heavy trailer, like a horse trailer or a large travel trailer, you're going to want to think about a diesel engine because there's a huge advantage for the diesel in terms of fuel economy.
When these vehicles are heavily loaded, as they typically are, the diesel engine could have a ten to twelve-mile-per-gallon advantage in fuel economy. The repairs may be more expensive but, over the long haul, you're going to save a lot on fuel. If your truck usage is light-duty and short trips, the gas engine is probably still your best bet - especially if your drivers on your vehicle are not with it in terms of the maintenance and how to care for a diesel engine. So this is one thing you want to think about if you're a business owner buying a truck for deliveries, think about the diesel engine and consider your usage.
Another thing that I advise my customers: if they've got a one-tonne truck and they're using it for heavy loads, in many cases, those owners, those business owners are better to move up to what we call a medium-duty truck with the larger wheels and tires, a much bigger chassis and a true truck diesel engine. It's got a heavier powertrain. You're probably talking about $10,000 to $15,000 more in the initial expense of the truck, but over ten years the repair costs are much lower on those trucks because they just play with the loads. They're not working hard to do the type of usage that many people are into. If you're hauling liquids or heavy loads that's the way to go. In terms of cars, though, not much choice today other than the Volkswagen TDI.
'Til next week, I'm Bill Gardiner for Motoring 2002.
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