Tag: Evergreen

  • Why MPG is a dumb unit for fuel economy

    Miles per gallon—mpg—is the default measure of gas mileage in the United States, but it may not be the best one, argues “Engineering Explained” host Jason Fenske. Here’s why he’d rather see a different unit of measurement for fuel economy.

    Fenske doesn’t have a problem with the individual units—the mile and the gallon—but says something “weird” happens when you put them together. He explains that with a question: Is it better to double the fuel economy of nine cars from 50 mpg to 100 mpg, or double the fuel economy of just one car from 5 mpg to 10 mpg?

    When just looking at efficiency, increasing the fuel economy of the nine 50-mpg cars is the best way to go. But once you factor in distance driven, it’s the other way around.

    Gas pump

    Gas pump

    That’s because mpg is a measure of distance (miles) per volume (gallon). Fenske notes at this point that most other countries flip this around, measuring fuel economy in volume per distance. In Europe, for example, the default unit is liters per 100 kilometers. Measuring fuel economy in gallons per mile would be more straightforward, he says.

    U.S. Corporate Average Fuel Economy (CAFE) targets are already calculated in a manner that’s closer to gallons per 100 miles, Fenske notes. They’re then converted back into mpg to make the numbers easier for the general public to understand, a process called a “harmonic mean.” Window stickers even show fuel economy in gallons per 100 miles in smaller print under the mpg figure.

    Increasing the mpg of two cars by the same amount also doesn’t mean they save the same amount of fuel. A gain of 1 mpg will equate to more fuel savings in a car that started out getting 5 mpg than a car that started out getting 50 mpg. Watch the full video to see the math supporting this, and if you want more efficiency, check out this video explaining how big tire sidewalls are your friend.

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  • 2021 Ferrari 812 GTS prances into Jay Leno’s Garage

    After checking out the mid-engine Ferrari SF90 Stradale, Jay Leno switched to the front-engine 812 GTS for a recent episode of “Jay Leno’s Garage.”

    The Ferrari 812 GTS is a convertible version of the 812 Superfast, sporting a retractable hardtop in place of the Superfast’s fixed roof. So it’s perfect for Leno’s Los Angeles locale.

    Like the 812 Superfast, the 812 GTS is powered by a naturally-aspirated 6.5-liter V-12, producing 789 hp and 530 lb-ft of torque. The engine drives the rear wheels through a 7-speed dual-clutch transmission. Ferrari quotes 0-62 mph in less than three seconds, with a top speed of over 211 mph.

    2021 Ferrari 812 GTS on Jay Leno's Garage

    2021 Ferrari 812 GTS on Jay Leno’s Garage

    When it was unveiled in 2019, the 812 GTS was the first V-12 Ferrari convertible since 2014’s limited-edition F60 America. In terms of regular production cars, it was the first since the 365 GTS/4 Daytona Spider of the early 1970s. However, Ferrari has since unveiled the 812 Competizione A, a more hardcore targa version with 812 hp.

    Leno was impressed by the design, noting that the V-12 front-engine cars are Ferrari’s traditional bailiwick. He liked the driving dynamics too, praising the smoothness of the V-12, the comfortable ride, and the handling precision of what is a fairly large car. A four-wheel steering system, shared with the 812 Superfast and originally from the F12tdf, likely helps with that.

    A hardcore version of the 812 Superfast is expected to be a swan song for the naturally-aspirated Ferrari V-12. So watch Leno take the 812 GTS for a spin, and listen to that V-12 wail.

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  • Should you use racing oil in your road car?

    Every part of a modern race car is optimized to extract maximum performance—including the fluids that go into it. Specialized racing oil is a must in the paddock, but is it a good idea to use that in your road car?

    “Engineering Explained” host Jason Fenske answers that question in this video, talking to engineers from Mobil1 (which also sponsored the video), engine builder Roush Yates Engines, and NASCAR team Stewart-Haas Racing.

    First off, Fenske emphasizes that racing engines don’t have much in common with road-car engines. Pushrod V-8s like the ones used in NASCAR disappeared from the average American car decades ago, and racing engines in general have a very different duty cycle. They’re flogged (a NASCAR V-8 can rev to 10,000 rpm and spend 90% to 95% of a race at full throttle), but also have fairly short maintenance intervals. NASCAR engines have their oil changed about every 500 miles and are only expected to last about 1,500 miles, Fenske noted.

    Ford Mustang NASCAR Xfinity Series race car

    Ford Mustang NASCAR Xfinity Series race car

    NASCAR oil is also fairly unrestricted (rules can vary by race series), giving teams more leeway to look for competitive advantages, Fenske said. Teams tend to use thinner-weight oils to reduce frictional losses and maximize power. That’s not great for longevity but, remember, the engine only needs to last 1,500 miles. Road-car engines, on the other hand, are expected to last hundreds of thousands of miles, so that kind of tradeoff isn’t possible.

    Racing oils and road-car oils do have some commonalities, though. They use a lot of the same additives, such as detergents, dispersants, anti-foaming agents, antioxidants, and rust inhibitors, Fenske noted.

    However, the difference is in the details. Oils used for road cars are designed to meet a long list of regulations and requirements set down by individual automakers. In NASCAR where, again, rules governing oil are fairly loose, teams can optimize an oil for one specific engine design. It’s really that process that makes racing oil work, and it’s just not practical for individual road cars. Unless you have your own laboratory and a lot of patience, at least.

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