2013 Volkswagen Passat TDI: Diesel #2 vs. B5 Biodiesel Comparison Results
May 19, 2014
It's over. I've completed two identical 458-mile loops to Las Vegas and back in our 2013 Volkswagen Passat TDI. The only difference was the fuel: Diesel #2 on the first loop and a B5 biodiesel brew on the second loop.
I say "biodiesel brew" because I was forced to MacGyver my own B5 by blending B20 biodiesel with Diesel #2 right in the Passat's tank. There wasn't another station close enough to be of any use, and I had just learned (the hard way) that the biodiesel locator Web site I'd used to find this place wasn't much use for finding anything under B20, the prevailing blend carried by suppliers around here.
Here's what I learned.
B20 biodiesel was 4 cents per gallon cheaper than the Diesel #2 sold at the same station. But there is an asterisk: If you pay with a credit card.
This Propel Fuels B20 pump is embedded in a Union 76 service station. The 76 pumps serve up a 12-cent cash discount. But the separately branded Propel Fuels B20 pump does not. Pay with cash and Diesel #2 is 8 cents cheaper than B20.
Call it a draw. The B20 was cheaper for me because I buy fuel on credit. I hate going inside to wait in line (twice) with the folks buying cigarettes, coffee or Gatorade.
Besides, the "savings" were even more negligible in this experiment because I only bought a quarter-tank (4.625 gallons) of B20 to brew my Loop 2 my cocktail.
No detectable difference. There are plenty of long grades to climb on this route. Cajon Pass and Baker Grade are the named ones, but there are others. I'd have noticed.
This was the surprise part.
Loop 1, Diesel #2: 11.484 gallons, 40.0 mpg (2.50 gallons per 100 miles)
Loop 2, B5 biodiesel: 10.446 gallons, 43.9 mpg (2.28 gallons per 100 miles)
I'm not sure what I expected going in, but I didn't expect the difference to be this sizable. It's a 9.6-percent improvement no matter how you look at it. I'm not entirely certain I believe it.
I controlled everything I could: identical route, identical time of day, identical speed. I duplicated the number of stops and I topped up the tank at the same pump and nozzle each time. Each loop even included a simulated city driving pattern that consisted of 22 stops with 2-minute idle periods.
The only thing I couldn't control was the wind. I had to drive into a strong Santa Ana wind during Thursday afternoon's outbound leg for perhaps 100 miles. Two days later the second loop's outbound leg had no such headwind.
I can safely say that performance using B5 doesn't suffer, subjectively, at least. And the price is about even. It also seems that any predictions of worsened MPG were unfounded. I'm not sure if our 9.6-percent observed improvement is absolutely correct, but it's pretty clear there was some improvement.
I plan to repeat this test with our new 2014 Ram 1500 EcoDiesel, which has two things going for it that may make this easier to sort out.
First, we have almost a year to work with. The Passat is leaving us very soon but the Ram just got here. We can repeat this sort of test several times if we want and we can measure acceleration at the track, too.
Secondly, the Ram can run on B20, which means the concentration of biodiesel will be four times greater. This should make it easier to pick out differences. We can always run it on B5, too, if we find it useful to mimic the conditions of this test.
Biodiesel's biggest problem from where I stand is simple availability. The Web site we used listed less than a dozen stations that sell B20 in the megalopolis that is the greater Los Angeles/Orange County/Inland Empire area. On a per capita basis biodiesel pumps are one in a million.
Dan Edmunds, Director of Vehicle Testing @ 20,629 miles