Buying guides for VW/Audi TDI and more diesel cars

Apr 17, 2017
Buying guides for VW/Audi TDI and more diesel cars
  • Welcome to the buying guide. Also visit our forum and read the FAQ/Wiki by clicking the tab at the top.

    This guide is from a frequent TDI owner who DIY all maintenance so you'll hear the good, the bad, and how to fix the bad. This page will let you quickly compare Volkswagen-Audi-Porsche diesel, why I prefer diesels over hybrids, and learn a little about the renewable fuel biodiesel. Detailed buying guides are linked from each section. For more detailed information such as maintenance intervals, recalls, and DIY "how to" for your car, see each section or the master index at 1000 answered questions: diesel FAQ-Wiki and "how to" index.

    Modern diesel cars and why they can get such high fuel economy

    If you think of diesels as the smoky, slow car from the 70's, think again. Modern diesels were clean burning, powerful, and reliable. The newest common rail technology cars are so quiet and clean that a bystander would never know the car is a diesel by the sound or smell. In fact, there's less soot on the exhaust pipe of the latest TDI clean diesels (the VW/Audi marketing name for diesel) than many comparable gasoline cars! Diesels account for about 50% of all new car sales in Europe and have much better fuel economy than a similar gasoline car. For example, the VW Lupo, a Europe-only subcompact Volkswagen, drove 20,000 miles around the world in a promotion, averaging over 80 miles/US gallon (2.5 liters/100 kilometers). A major concern for modern cars is improving fuel economy and emissions, so until VW dieselgate, diesel were growing in market share in North America. Audi, VW, BMW, and Mercedes Benz all had multiple diesel models for sale in the US. In the long term cars will probably be hydrogen fuel cell or fully electric powered. In the far future I'm sure we'll all be flying around on personal jetpacks circa the 1962 world's fair (probably not :))

    VAG (Volkswagen auto group) owns Audi and Porsche so their diesels all share common components. Their offerings in North America are turbocharged and intercooled 4 or 6 cylinder engines that use direct injection, a technology that is only now being put into a few gasoline cars. Larger/sportier diesel passenger cars like BMW or MB and trucks use 6 or 8 cylinder engines. The largest engine for North American TDI was the twin turbo V10 in the Volkswagen Touareg. Europe even had the option of the V12 VW Touareg TDI and Audi Q7 TDI!

    Some of the major reasons why diesel engines get better mpg is because of the engine design and fuel. Diesel fuel contains more energy per gallon and run very lean (a higher air:fuel ratio) so they can do more work off less fuel. The combustion process also produces less waste heat, meaning more of the energy is translated into work. All diesels are high compression so the engine can get more energy out of each combustion cycle. Engine RPM is controlled by fueling and not a throttle, meaning parasitic pumping losses off the engine are reduced. Modern diesels are all direct injection, meaning the fuel is compressed under very high pressure and sprayed directly into the combustion cylinders. They are also all turbocharged, which can increase fuel economy, depending on engine design and power load.

    Dieselgate and the future of light diesel cars
    When I originally wrote this buying guide overview, light diesel cars were growing dramatically in market share, becoming 20% of VW's annual US sales, with models being introduced from Audi, Porsche, Mercedes, BMW, and Chevy. During late 2014, it was found that VW TDI were not meeting emissions. 2015, it was found that the car's computer on VAG (VW auto group - includes Audi and Porsche) TDI was looking for conditions like emissions testing, to trigger alternative programming and pass emissions. When the cars saw they were not being emissions tested, they increased harmful emissions. The public relations disaster resulted in billions of dollars in penalties and losses for VAG and the ending of their light diesel sales.

    While Mercedes, BMW, and Chevy light diesels were never implicated in "dieselgate", they have since considered withdrawing their light diesels based on changing market conditions. You can read a timeline and FAQ of dieselgate in my wiki-FAQ article here. This doesn't mean an end to diesel technology though - VAG plans to continue to sell 6 cylinder Touareg, Cayenne, and Q7 diesels, and domestic brand pickup trucks will definitely continue to have diesel engine options since they're used for towing and industrial purposes.

    Light diesel cars vs. hybrids

    Why not a hybrid? They're a good solution to reducing emissions and increasing fuel economy. However, I prefer the current diesels in the marketplace than the hybrids in the new and used car marketplace. There's a lot more to driving than fuel economy. If fuel economy were everything then you can't beat riding a bicycle! Why even bother mentioning hybrids on a diesel site? Because most people know that hybrids give great fuel economy but aren't even aware that there are diesel cars for sale in North America. Because of their high fuel economy, there will be some cross shopping between types.

    The pros/cons of a diesel or hybrid are also dependent on your driving style and whether you make mostly short local trips or longer highway commutes. I also like driving manual transmission cars and there is no manual hybrid. (The Honda CRX hybrid coupe was recently sold with a manual and is the one exception). There must be something unique about diesel drivers because I've noticed the percentage of TDI sold with manual transmission cars is a lot higher than most other cars. Until they make a large Prius station wagon, the Jetta and Passat station wagons have an unbeatable blend of economy and cargo room. Compare the newest Jetta TDI sportwagen with 67 cu ft of max cargo room plus a roof rack with the newest Prius and 40 cu ft. Your fuel economy may vary and people boasting about their car normally give their personal bests. Diesel engines also take thousands of miles to break in before reaching peak fuel economy and this is reflected in new car testing. Below are some comparisons between a diesel vs. a hybrid. Ultimately it's a question of values and economy.

    Although hybrids do have cleaner emissions and limited High Occupancy Vehicle (HOV lane or carpool) access, diesels that use the 100% renewable and homegrown fuel biodiesel have greener emissions than a hybrid. And while every little bit helps, I've found that the majority of those who tout the lower CO2 emissions of a hybrid are not sincere in making other lifestyle choices to further reduce CO2 emissions. City living so you can use mass transit and drive far less, small apartments so you build and heat less empty living space, and vegan diets to reduce the high CO2 emissions from meat/milk/eggs production are attainable, affordable, and could have a much greater effect on conservation than just buying a hybrid with no other change in lifestyle. It's not reasonable or correct to claim righteousness when your change in lifestyle is convenient to you while rejecting the validity of another's values. Somewhere there's a bike riding freegan (non homeless people who eat non spoiled food out of public trash) wearing used clothes criticizing a Prius driver! I care about the environment but don't want a bike riding freegan lifestyle since my values are different and are my own. Again, it comes down to a matter of values and economy. To make a direct comparison to a gasoline non-hybrid, the Volkswagen Jetta TDI has about 25% lower CO2 emissions than the basic 2.5L gasoline engine Jetta.

    A diesel may also be more economical in the long run over a hybrid. Comparing the same year Prius and Jetta, a Prius should have better average reliability. But the Jetta has better safety ratings, standard safety equipment, and should last longer. (A light diesel can last up to 300-400,000 miles with regular maintenance and upkeep because it has cooler running temperatures, operates at lower RPM, and diesel fuel is an oil. Start/stop can be harder on engines than constant normal running.) It's more economical to buy a diesel and drive it for 20 years with minor repairs but you won't have the newest technology. A dust-dust analysis of energy put into a Prius favors a new car past a relatively low mileage if newer technology comes out (in reality that car is sold to another person as used) but buying new cars every few years will cause you to pay all of the depreciation cost. The Jetta diesel has excellent aftermarket support since it shares suspension and other parts with similar VW gasoline cars, letting you add an aggressive sport suspension or other aftermarket parts. What do you value and how much are you willing to pay for it?

    The biggest disadvantage of hybrids is the additional cost and weight of the hybrid technology. The current generation of hybrids cost $3,000-10,000 more than a comparable non hybrid car, a cost that you will probably not recoup in fuel savings. The largest flagship luxury hybrids use V8 engines which use the hybrid label as a greenwashing gimmick. Many hybrids are also merely electric assist and not full hybrids, meaning that they cannot run on electric alone, reducing the advantages of buying a hybrid. The Chevy Volt has this capability but the estimated MSRP of the car is $40,000, significantly higher than TDI even after federal tax credits. The Fisker Karma, a lithium-ion plug in hybrid, was a great car with exclusivity, style, and technology but with a starting price of $80,000 it's a niche within an expensive niche. They also went out of business. The Nissan Leaf is a full electric car but it has a limited range and owners report real world range significantly lower than advertised. The Chevy Malibu mild hybrid had start/stop and a mild hybrid system but it was panned in reviews as not worth the additional cost, not well integrated, and was discontinued.

    The manufacturers who make hybrids vs. diesel also have different ideas about luxury and design. VW and Audi have class leading interior design compared to the strange Prius or Lexus HS250h interior. Compare the Lexus interior on the right with the Audi A3 interior below left - the A3's interior is much cleaner and richer. The Lexus has a joystick controller stuck onto the center console which juts out with buttons and stalks scattered everywhere. While the higher screen is easier to view, the driver's primary focus should always be safe driving.
    [​IMG] [​IMG]

    Hybrids also have compromises in the driving experience to maximize fuel economy. For example, a leading hybrid uses cheap, narrow, and hard tires to maximize fuel economy and the EPA test mileage. These tires are among the worst rated on tirerack's survey! Everything else being equal, hard narrow tires increase fuel economy but reduce handling and braking. In hybrids with regenerative braking, the limiting factor in braking is not braking force, but tire grip. Any more braking force cannot be put to the ground to slow the cars or else the tires will lose their grip and force electronic stability control to reduce braking. Using grippier, wider tires with more traction would increase handling and braking but at the cost of reducing fuel economy.

    I believe that driving pleasure and choice of car should be a balance of your needs and wants between sportiness, comfort, fuel economy, price, practicality, and safety, and that hybrids sacrifice some of these qualities. I believe that people can enjoy great freedom and pleasure when driving and that cars are more than just an appliance that takes you from point A-B as economically as possible. Those are my values. Ultimately, your values are what matters so test drive a Volkswagen or Audi TDI and then drive a Prius and compare them yourself. If your greatest priority is fuel economy and you can't tell the difference in handling, driving feel, interior quality, and design, then getting a Prius or another car is honestly a good option. Again, the best car for you is one that matches your needs, not mine.

    The future will have much better gasoline hybrid cars and I think electric cars will dominate the long term future. Electric-diesel hybrids are planned but by then, electric-gasoline hybrids and full electric cars will have advanced as well so it's only fair to judge what is here now. For a different perspective, here is the conclusion from an article in Autoweek comparing the Prius, a Jetta TDI, and a few other cars in a real world fuel economy test. The testers made the same conclusions as myself on driving feel and real world fuel economy vs. EPA estimates.
    "TOYOTA PRIUS: 8.3 gallons of regular gas at $2.599/42 mpg vs. EPA highway rating of 51 mpg

    Well, it didn’t make its 51-mpg EPA highway estimated, but 42 mpg on a long road trip would please most American drivers...That instant feedback loop, monitoring economy in short increments of time and distance—not to mention letting the driver see exactly where the energy is going to and coming from—is a big part of why Prius drivers are so prone to telling the rest of us, “You have to drive it differently.” We found that isn’t quite true; the Prius responds to the same economy-minded driving techniques experts have been advising for 30 years or more. ...The difference in the Prius is it offers up immediate gratification of the video-game variety, right there on the dashboard, no waiting to fill the tank and do the math yourself. ..It did really well. It just wasn’t the mileage champion.

    VOLKSWAGEN JETTA TDI: 7.0 gallons of B20 biodiesel at $2.749/ 49.9 mpg vs. EPA highway rating of 42 mpg

    Our fuel station was offering up B20 biodiesel, 20 percent of which comes from vegetable oil, animal fats and other sources, meaning that from an environmentalist’s perspective the German diesel didn’t just beat the Japanese hybrids, it trounced them. Not only that, it had more than half of its 14.5-gallon tank left at the end—it could have made the same trip again without refueling! Our example was pretty much a stripper, absent even the usual VW trip computer, so we had no instant feedback loop on our performance. Maybe if we’d had that, we could have nudged the economy from 49.9 mpg into the 50-mpg highway speeds its 177 lb-ft at 1800 rpm and 100 hp at 4000 rpm feel stronger than the Toyota and smoother than the Honda. The diesel spins harder than the Vette at 80 mph, running at 2500 rpm or so, but still it is a long-legged German car with autobahn-able credentials.

    For comfort, quiet and highway handling, our drivers found the TDI had significant advantages over every other car in the test. It would have been our choice, in other words, for an easy daytrip on the interstates, regardless of fuel economy. And we topped the hybrids by driving with just a little attention to fuel economy, not making it an obsession."

    Here is a video review from edmunds - "based on value, comfort, and fun, the 2009 VW TDI is the smarter choice and the car we choose over the current Prius." If they had reviewed the station wagon they would have found much more cargo room plus a roof rack and no penalty in economy due to identical weight. Below is another review comparing the Audi A3 TDI and VW Jetta TDI vs. Smart vs. the Insight, Prius, Smart, and Fusion hybrids.
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