As a former grease-car guy, how can I flip-flop and not favor diesels over gasoline? In short, the answer is that while diesels are more efficient in mpg compared to cheap, poorly built gasoline vehicles, the diesel advantage mostly goes away when you compensate for the fact that diesel fuel has 10.1 Kg of CO2 emissions per galllon of fuel burned while gasoline only has 8.8 Kg of CO2 (Numbers taken from EPA site).
Don't get me wrong, there are still great advantages to diesels. Diesels have lots of torque and drive great. I drove a 2011 Audi Q7 diesel and it is quite car ($65,000). However, it's carbon emissions are not anything to write home about compared to a gas powered, 7-passenger, car-based SUV like a Ford Explorer or Flex or a Honda Pilot.
What about biodiesel? Well, I do love biodiesel and the movement is awesome. It's Nopec. It's clearner burning. But it has it's drawbacks. Biodiesel is hard to find in many places. It takes a lot of energy and time inputs to create biodiesel.
If you enjoy working in your shed and diving in grease dumpsters to salvage waste vegetable oil, you can create biodiesel through transesterification with methanol and NaOH. Sure, you get lots of toxic co- and byproducts to deal with and your fuel won't work in the winter because it gels. Oh wait, that's part of the reason.
Until we have electric vehicles that can trade out batteries at stations along the highway, we'll need some liquid fuel to run our cars. How much better are diesels? How do the calculations work out? Should we all switch to diesels?
Diesels emit 12.8% more CO2 for every gallon of fuel they burn. Diesel Fuel also costs 7.7% more than gasoline. When you include those two factors and compare them to equally sophisticated gasoline engines, all of the advantages go away and the two fuels are equally bad. My caveat is that if you're burning biodiesel and supporting an organization like Piedmont Biofuels, then I'm all for it. Until there's a price on net carbon emissions, you'll have to come up with extra cash for that.
If you look at 2 Volkswagen models you get a feel for the payoff of using diesel. The Toureg and Toureg diesel have price differentials of $3600 more for the diesel and fuel usage differentials of $306 more dollars per year for the gasser. Thus, the payoff for a Toureg diesel (not accounting for resale value, which will be better in the diesel) occurs after 10.8 years. For a Jetta Sportwagen versus a Jetta Sportwagen Diesel, the price differential at the outset is $4600 and the differential per year in fuel is $168.70 more for the gasser. It would take 28 years to pay for the diesel not including the added resale value of the diesel or depreciation on the cost benefits because they come in the future. In short, it doesn't pay from a fuel perspective to get a diesel sportwagen, even though those EPA numbers in MPG again look better than they are.
It's surprising to read these figures, and the carbon emission figures are similar. The Toureg diesel only saves 61 Kg of CO2 per year. The Sportwagen diesel saves 297 Kg of fuel per year. Thus, while both are better, they don't approach the massive savings that hybrids provide by using regenerative braking and stop-start technology to save fuel.
The numbers are below:
Don't get me wrong, there are still great advantages to diesels. Diesels have lots of torque and drive great. I drove a 2011 Audi Q7 diesel and it is quite car ($65,000). However, it's carbon emissions are not anything to write home about compared to a gas powered, 7-passenger, car-based SUV like a Ford Explorer or Flex or a Honda Pilot.
What about biodiesel? Well, I do love biodiesel and the movement is awesome. It's Nopec. It's clearner burning. But it has it's drawbacks. Biodiesel is hard to find in many places. It takes a lot of energy and time inputs to create biodiesel.
If you enjoy working in your shed and diving in grease dumpsters to salvage waste vegetable oil, you can create biodiesel through transesterification with methanol and NaOH. Sure, you get lots of toxic co- and byproducts to deal with and your fuel won't work in the winter because it gels. Oh wait, that's part of the reason.
Until we have electric vehicles that can trade out batteries at stations along the highway, we'll need some liquid fuel to run our cars. How much better are diesels? How do the calculations work out? Should we all switch to diesels?
Diesels emit 12.8% more CO2 for every gallon of fuel they burn. Diesel Fuel also costs 7.7% more than gasoline. When you include those two factors and compare them to equally sophisticated gasoline engines, all of the advantages go away and the two fuels are equally bad. My caveat is that if you're burning biodiesel and supporting an organization like Piedmont Biofuels, then I'm all for it. Until there's a price on net carbon emissions, you'll have to come up with extra cash for that.
If you look at 2 Volkswagen models you get a feel for the payoff of using diesel. The Toureg and Toureg diesel have price differentials of $3600 more for the diesel and fuel usage differentials of $306 more dollars per year for the gasser. Thus, the payoff for a Toureg diesel (not accounting for resale value, which will be better in the diesel) occurs after 10.8 years. For a Jetta Sportwagen versus a Jetta Sportwagen Diesel, the price differential at the outset is $4600 and the differential per year in fuel is $168.70 more for the gasser. It would take 28 years to pay for the diesel not including the added resale value of the diesel or depreciation on the cost benefits because they come in the future. In short, it doesn't pay from a fuel perspective to get a diesel sportwagen, even though those EPA numbers in MPG again look better than they are.
It's surprising to read these figures, and the carbon emission figures are similar. The Toureg diesel only saves 61 Kg of CO2 per year. The Sportwagen diesel saves 297 Kg of fuel per year. Thus, while both are better, they don't approach the massive savings that hybrids provide by using regenerative braking and stop-start technology to save fuel.
The numbers are below:
| Car | MPG | Miles driven | Gallons | Fuel Cost | Savings | CarPrice | Payoff Time(yr) | CO2 (KG/G) | YearlyOutput | CO2 Saved |
| Toureg | 19 | 15000 | 789.5 | 2644.7 | 42882 | 8.8 | 6947.4 | |||
| Toureg Diesel | 22 | 15000 | 681.8 | 2338.6 | 306.1 | 46199 | 10.8 | 10.1 | 6886.4 | 61.0 |
| Jetta Sportwagen | 27 | 15000 | 555.6 | 1727.8 | 21150 | 8.8 | 4888.9 | |||
| Jetta Sportwagen TDI | 33 | 15000 | 454.5 | 1559.1 | 168.7 | 25973 | 28.6 | 10.1 | 4590.9 | 298.0 |
