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Lean Burn Technology Vehicles

Last updated 29th Nov 2022

In the never-ending drive to squeeze more miles per gallon of fuel, automobile manufacturers are once again turning to lean burn technologies. The government showed its support for this equipment when it passed the Energy Policy Act of 2005. Cars, trucks, and SUVs certified as advanced lean-burn vehicles qualify for tax credits as high as $1,800 under the provisions of that law.

In this article, we're going to briefly discuss the theory behind lean-burn technology. As part of that discussion, we're going to provide some fuel economy numbers for one of the first lean-burn cars to hit the market. Finally, we'll supply a list that outlines the five makes and models of vehicles that qualified for tax credits.

Update: As of 2011, all tax credits on hybrids, plug in hybrids, lean burn diesels, and alternative fuel vehicles have been eliminated. Electric vehicles may still be eligible for a federal income tax credit of up to $7,500.

Lean-Burn Theory

The initial lean-burn system was introduced by Chrysler back in 1976. This system consisted of a series of sensors and electronics that would adjust the engine's spark advance under a variety of driving conditions. This technology was able to provide increased engine performance, as well as improved fuel economy.

The automotive challenge that lean-burn is trying to overcome has to do with throttling losses. A car's engine must be large enough to provide the power necessary for acceleration, yet operate well below its potential output when driving at cruising speeds.

The optimal air to fuel ratio at cruising speeds would be very different from the mixture needed during acceleration. In fact, the ultra lean ratio necessary to achieve the desired increase in MPG is only accomplished by direct injection into each cylinder.

The primary disadvantage of lean-burn technology is the amount of NOx that is generated at this higher air to fuel ratio, as well as developing a catalytic converter that is compatible with these systems. Until the 2008 / 2009 model year timeframe, this had been an especially difficult problem to overcome with diesel-powered engines, which have a slight energy efficiency advantage when compared to gasoline-powered engines.

Advanced Lean-Burn Engines

Today's advanced lean-burn diesel and gasoline vehicles utilize sophisticated, and expensive, combustion systems along with superior emissions technologies. This combination allows these cars and trucks to achieve outstanding mileage performance under both city and highway driving conditions.

In addition to the fuel economy advantage of these vehicles, the design of these engines results in high torque power relative to the engine's horsepower rating. For consumers this means not only savings at the fuel pump, but also a driving experience that includes a car that accelerates quickly.

The table below provides a quick comparison of the 2011 Volkswagen Jetta S and the Jetta TDI, which is equipped with a clean diesel, turbocharged engine. The TDI runs on ultra low sulfur diesel fuel, resulting in reduced vehicle emissions. The lean-burn technology is also responsible for a 95% reduction in sooty emissions.

Volkswagen Jetta SVolkswagen Jetta TDIMSRP$17,340$21,990Tax Credit0$1,300MSRP after Tax Credit$17,340$20,690Highway Mileage (MPG)2130City Mileage (MPG)2941

Tax Credits for Lean Burn Technologies

As part of the Energy Policy Act of 2005, the Internal Revenue Service provided for tax credits for hybrid vehicles as well as lean-burn technology motors. In February 2011, the IRS certified the following six vehicles as qualifying for tax credits:

  • 2011 Mercedes Benz E350 BLUETEC ($1,550 credit)
  • 2011 Mercedes Benz GL350 BLUETEC ($1,800 credit)
  • 2011 Mercedes Benz ML350 BLUETEC ($900 credit)
  • 2011 Mercedes Benz R350 BLUETEC ($1,550 credit)
  • 2011 BMW 335dSedan ($900 credit)
  • 2011 BMW x5 xDrive 35d Sedan ($1,800 credit)

To qualify, vehicles must incorporate direct fuel injection technology, and achieve at least 125 percent of the city fuel economy rating for the 2002 model year. The tax credits themselves vary according to the fuel economy rating, and the vehicle's projected lifetime fuel savings.

Qualifying for the Lean Burn Tax Credit

To claim a tax credit for a lean-burn vehicle, the taxpayer must be the vehicle's original owner; resellers are not entitled to take this credit. As is the case with hybrid vehicles, there is a phase-out period for this credit once the manufacturer has sold 60,000 units.

The phase-out schedule for vehicles qualifying for a tax credit is based on time, not additional vehicles. The measure of time for the phase-out is calendar quarters. Once the 60,000th sale is recorded, the phase-out and credit by calendar quarter is:

  1. During the calendar quarter in which the 60,000th vehicle is sold: 100% tax credit
  2. During the second and third calendar quarters after which the 60,000th vehicle is sold: 50% tax credit.
  3. During the fourth and fifth calendar quarters after which the 60,000th vehicle is sold: 25% tax credit.
  4. Taxpayers are not entitled to a tax credit for an advanced lean burn vehicle after the fifth calendar quarter.

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Moneyzine Editor

Moneyzine Editor