Why We Bought It
Durability
Performance and Fuel Economy
Retained Value
Summing Up

We are in the pre-dawn hours of 2008. Stock markets are faltering on a global scale. Crude oil demand is on the rise and tightening its stranglehold on the petroleum-reliant consumers of the world. Automakers can't produce hybrid vehicles fast enough. Even gasoline-loving Americans are considering the benefits of diesel fuel. Panic is on the horizon.

From this environment emerges new interest in the growing alternative fuels movement. In anticipation of this paradigm shift, Inside Line earmarked funds from our 2007 long-term test car budget to add another alternative-fuel vehicle to the fleet. So in the final days of 2007 we purchased a certified pre-owned 2005 Volkswagen Jetta GLS TDI. We did so with the intention of converting the TDI to a biodiesel alternative fuel.

Why We Bought It
Our plan for the Jetta TDI was two-pronged. We would buy a certified pre-owned Jetta and document the used car purchase and maintenance experience as a secondary test. Our primary test involved taking the Jetta TDI and transitioning it from petroleum-based diesel fuel to dinosaur-free biodiesel. Numerous questions would arise as we tested our Volkswagen Jetta TDI with biodiesel.

How will the fuel system hold up to B99 grade fuel? How drastic will fuel economy vary between petrodiesel, B20 and B99? Where do we purchase biodiesel? We would answer all these questions and more between the introduction of the car 17 months ago and its conclusion.

Durability
Our test of the 2005 Volkswagen Jetta TDI focused less on how the car drove and more on the use of biodiesel. But we can assure you this 2005 variant offered all of the driving characteristics we've come to expect from a Jetta. This is a comfortable, fuel-sipping commuter car. Gearshifts are simple and clutch pedal effort light. There is just enough low-end torque from the 1.9-liter turbodiesel to get out of the gate but no more. Body roll is significant and the ride is arguably too compliant. Just ask Senior Road Test Editor Josh Jacquot. Jacquot wrote, "This is a silly little car. Primarily this is because it's way too soft. And by soft I mean wallowing, pitching, diving, rolling and ruthlessly punishing its bump stops at every opportunity. It feels like it's sprung by marshmallows and damped by a weak will. If this is how Volkswagens feel at 67,500 miles, well, I'm out."

Inside the cabin we could certify the Jetta was pre-owned. Grease stains on the headrest, cloudy window tinting, a decrepit seat bolster and a cornflake armrest were all obvious signs of previous ownership. But we knew about these when we bought it. Each issue was remedied at minimal cost and we chalked them up to normal wear and tear. We replaced both headlight bulbs when they burnt out at 60,000 and 63,000 miles. All typical ownership experiences for a car with more than 50,000 miles. Service at the recommended 10,000-mile intervals helped ensure our Jetta remained impervious to the reliability stigma often attached to high-mileage VWs. Our transition to biodiesel created some of its own problems.

The switch to biodiesel seemed simple enough. We began with a partial B20 blend (20 percent biodiesel/80 percent petrodiesel) in an effort to break the car in slowly but moved to B99 (99 percent biodiesel) by our next fill-up. Biodiesel acts as a solvent and loosens deposits throughout the fuel system, from tank to injectors. So we bought reserve fuel filters in anticipation of their overload. A sputter at startup just 800 miles into the B99 era provoked our first fuel filter replacement. Our second filter lasted 9,000 miles before succumbing to the fate of its predecessor. Two filters marked the only detrimental effects of B99 witnessed during 12,000 miles of driving on biodiesel.

Total Body Repair Costs: None
Total Routine Maintenance Costs (over 17 months): $372.10
Additional Maintenance Costs: $104 for two fuel filters and two headlight bulbs
Warranty Repairs: None
Non-Warranty Repairs: None
Scheduled Dealer Visits: 1
Unscheduled Dealer Visits: None
Days Out of Service: None
Breakdowns Stranding Driver: None

Performance and Fuel Economy
We purchased the 2005 Volkswagen Jetta TDI at 51,000 miles and promptly sent it to be tested. A quarter-mile stroll down the drag strip lasted 17.3 seconds at 73.9 mph, with the Jetta reaching 60 mph in a leisurely 11 seconds. These marks slowed to 18.4 seconds at 73.4 mph and zero to 60 in 12 seconds by its final test at almost 70,000 miles. Chief Road Test Editor Chris Walton asked following the final test, "What's up with the fuel delivery — or lack thereof? There is an unexplained intermittent engine cutout. It absolutely affected acceleration runs." We could not determine whether this decrease in output was a result of the biodiesel coursing through its veins or the Jetta merely aging. But fuel economy is the real gauge of performance when it comes to the Jetta TDI. We measured the Jetta's consumption using both variations of diesel.

Petrodiesel fueled the Jetta for the first seven months and 8,000 miles of our test. During this time the average single tank burned at a rate of 39 mpg, the best at 49 mpg and the worst at 26 mpg. We filled the VW with biodiesel for the remainder of the test: 10 months and 12,000 miles. As documented on the long-term blog pages, we averaged 40 mpg on biodiesel, with a best tank of 50 mpg and a worst of 30 mpg. Nearly identical fuel economy makes a strong argument for the case of biodiesel. We were fortunate that the two stations we used to refuel the Jetta were supplied by reputable producers of biodiesel. That isn't always the case.

On paper, biodiesel quality standards in the U.S. are stricter than those regulating gasoline and petrodiesel production. But in practice this doesn't guarantee high quality. At this time, biodiesel producers follow regulations on a voluntary basis. This is bad news for consumers, who may experience performance inconsistencies between one fill-up and the next. Automakers generally frown on biodiesel usage for this reason, many to the point of voiding warranties. This fuel is struggling to gain acceptance as a viable alternative to mainstream diesel and is highly susceptible to economy swings. Recent economic woes are a case in point. We received a formal letter warning of the shutdown of our local station. Apparently there is a pocket of biodiesel users in West Los Angeles, as local outcry spared it in the end.

Best Fuel Economy: 50 mpg (bio); 49 mpg (petro)
Worst Fuel Economy: 30 mpg (bio); 26 mpg (petro)
Average Fuel Economy: 40 mpg (bio); 39 mpg (petro)

Retained Value
We purchased our pre-owned Jetta for $17,200 and accumulated almost 20,000 miles before placing it on the auction block. Edmunds' TMV^® Calculator appraised the VW at $12,900 at the time of sale.

When the time came to offer the Jetta at TMV pricing, there were few takers. We listed the sale on Craigslist, Autotrader and Cars.com, which generated just one e-mail inquiry and two phone calls. After almost six weeks of trying to sell the vehicle, it was purchased by a Craigslist user for $11,900. That equated to depreciation of 31 percent. We deemed this a fair price considering the vehicle was about due for tires and its 70,000-mile service.

True Market Value at service end: $12,900
What it sold for: $11,900
Depreciation: $5,300 or 31% of original paid price
Final Odometer Reading: 69,967

Summing Up
We purchased a 2005 Volkswagen Jetta TDI with two goals in mind: Document the quality of a car purchased through the certified pre-owned car program and convert the car to biodiesel. We succeeded on both accounts and learned quite a bit about alternative fuels in the process.

From a used-car standpoint, the Jetta was near perfect. Minor cosmetic issues and two burnt-out headlamps were the only items requiring attention. We used cleaning supplies that were on hand and replaced both bulbs for less than a General Grant. An acceptable price considering the Jetta's mileage had already eclipsed the half-century point. We can live with this normal wear and tear.

When it came to the biodiesel project, we met some resistance. Numerous obstacles still impede the acceptance of biodiesel as a reliable alternative fuel. Regulation of fuel production is the most ominous. An honor system method of quality control is obviously not ideal. Until this is fine-tuned, most automakers will not back the fuel. That should be a concern for consumers. High levels of deposits released into the fuel system should also be monitored. We experienced performance degradation in the Jetta over time. Our test could not determine whether fuel type contributed to this, however.

The benefits of biodiesel may not yet outweigh the risks, but they do show promise. A network of fueling stations already exists that offer pure and diluted blends of the anti-diesel. Fuel economy is a strong catalyst in support of this cause. We found that B99-grade fuel has the potential to burn as efficiently as its petroleum-based counterpart. And it does so with a renewable resource.

Edmunds purchased this vehicle for the purposes of evaluation.