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Introduction
Welcome to the myturbodiesel buyer's guide. Whether you're new to diesels or know a lot, this page will let you quickly compare available diesel cars, learn a little about the renewable fuel biodiesel, and why I think diesels are better than hybrids. For more detailed information such as technical specs, maintenance intervals, recalls, technical service bulletins, and "how to's" for your car, go to the bottom of that car's section for it's detailed specs link, or refer to: 1000 answered questions: diesel FAQ and "how to" index
If you have any memory of diesels as the same smoky and slow cars of the 70's, think again. If you have not driven a diesel lately, you are in for a surprise! Today's diesels are cleaner 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. They account for about 50% of all new car sales in Europe and have much better fuel economy due to the combustion process and energy content of the fuel. For example, the VW Lupo, a Europe-only subcompact Volkswagen, drove 20,000 miles around the world in a test, averaging over 80 miles/US gallon (2.5 liters/100 kilometers). A major concern for modern cars is improving fuel economy and emissions, so I believe that diesels will have a much larger market share in the short term US market. Honda, Acura, Audi, VW, BMW, and Mercedes Benz, are all bringing or have already have diesels in the US.
This section has both basic and advanced facts here, so I hope everyone can find something interesting. For a more advanced and detailed description of diesel mechanics, diesel systems, and turbos, refer to 1000 answered questions: how a diesel works and 1000 answered questions: turbocharging. If you are interested in running biodiesel, please read 1000 answered questions: biodiesel.
Most passenger car diesels are turbocharged and intercooled 4 cylinder inline cast iron engines that use direct injection, a technology that is only now being put into a few gasoline mass production cars. Larger diesel passenger cars and trucks are more likely to use 6 or 8 cylinder engines that are either inline or in a V configuration. Among the largest passenger car diesel engines is the Volkswagen V-10 twin turbo diesel engine. They also use electronic throttle and control of the fuel systems, which give better fuel economy and performance.
Among the basic differences between a modern gasoline and diesel engine is that
most gasoline engines use low pressure gasoline sprayed
into the intake right before the combustion cylinders. The air/fuel charge is compressed and burned
by a spark plug igniting the
fuel, then the spent fuel goes out the exhaust. A modern diesel engine uses high pressure fuel sprayed
directly into the combustion cylinders at extremely high pressures. The air/fuel
charge is compressed to much higher pressures and
detonates, a form of compression ignition without the use of a spark plug. Some gasoline cars can also burn
ethanol or a gas/ethanol mixture, both of which are incompatible with diesel engines, and diesel cars can burn
biodiesel or a biodiesel/diesel
mixture, which is incompatible with gasoline engines. Obviously, you cannot use diesel fuel in a gasoline car or vice versa
because the fuels are incompatible. Almost all modern diesel engines are also
turbocharged, most gasoline cars are nonturbo.
Some other major differences include the engine oil that a diesel engine
prefers. Diesel specific engine oils are approved for 10,000 mile oil
changes, are specially designed for long life and to hold diesel soot. A gasoline
specific engine oil will not lubricate a diesel engine properly. Partially
due to lower rpm operation than
a comparable gasoline engine, lower heat, and more sturdy construction, diesel engines are known for lasting up to 400,000 miles and beyond with proper
maintenance
and proper lubrication when you use the correct oil. The "how
to" page and detailed model specification page has links to a list of the
correct oil for your car, see 1000 answered questions:
diesel FAQ and "how to" index.
Why not a hybrid? I personally like the idea of gasoline electric hybrid cars. They are a good solution to reducing emissions and increasing fuel economy. However, it is my opinion that the diesels offer more advantages than hybrids in the current new and used car marketplace. If fuel economy were everything then ride a bicycle! The pros/cons of a diesel or hybrid are also effected by driving style and whether you drive mostly short local trips or longer highway commutes. For longer highway commutes, a diesel is better due to the much longer range and steady cruising. VW diesels were designed for the Autobahn and handle as such.
The biggest disadvantage of hybrids is the additional cost of the hybrid technology. The current generation of cars costs $3000-10,000 more than a comparable non hybrid car, a cost that many cannot afford and a cost that you will not recoup in fuel savings. They also incur a weight penalty due to the extra equipment. The largest hybrids use V8 engines put into flagship luxury cars and the hybrid label is used 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.
Another problem is that full hybrids are designed with compromises to maximize fuel economy. For example, a leading hybrid uses cheap, narrow, and hard tires to maximize fuel economy and the EPA test mileage. This leading hybrid's tires were among the worst rated on tirerack's survey! Smaller, harder tires increase fuel economy but reduce handling and braking. Everything else being equal, 5 feet of increased braking distances during an emergency stop may be the difference between rear ending someone and avoiding an accident. In hybrids with regenerative braking, the limiting factor is not braking force, but tire grip. Any more force cannot be put to the ground to slow the cars or else the tires will lose their grip, possibly inducing a slide or skid and forcing electronic stability control to reduce applied braking force. Using softer tires with more traction would increase handling 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 sporty-ness, comfort, fuel economy, price, practicality, and safety, and that many hybrid drivers sacrifice some of these qualities with their hybrids. I believe that people can enjoy an amazing level of freedom and pleasure when driving and that driving is about more than getting from point A-B as economically as possible. I feel that the current generation of full hybrids are missing a lot that the currently available diesel cars have. To prove this, test drive a Jetta TDI and then drive a Toyota Prius. If your greatest priority is fuel economy and you can't tell the difference in road noise, handling, interior design, and driving feel, then getting a Prius or another car is honestly a better choice. Again, the best car is a car that matches your needs, not mine.
EPA fuel economy testing also is more realistic in hybrid cars than diesel cars. One bias is because diesel engines take many thousands of miles to sufficiently break in before reaching peak fuel economy, EPA numbers are about correct for hybrids but a low estimate for diesels, assuming an average driver.
The future will have much better gasoline hybrid cars, but I feel that there is a lot lacking in the current generation. For example, plug in technology could have greatly extend the range a hybrid when operating on electric only. The engineering knowledge exists but was avoided not only for the additional cost, and minor engineering challenges, but also for marketing, to dispel the myth that hybrid cars have to be plugged in. I think it will only be a matter of time before you see electric-diesel hybrids with fuel economy in the 60-80 mpg. By then, electric-gasoline hybrids will have advanced as well, so who knows what will be better in 10 years.
For now, the only areas which hybrids are definitely superior to diesel cars is in emissions and High Occupancy Vehicle (HOV lane or carpool) access. However, if you take into account biodiesel use, a 100% sustainable fuel, diesels can have greener emissions than a hybrid. The future car marketplace will probably include more hybrids and diesels, but for current cars on the market, I believe that diesels are cheaper to buy, greener with biodiesel, better handling/torque, better range per tank, better looks, better resale value, and engines that will last 400,000 miles with proper maintenance.
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. http://www.autoweek.com/apps/pbcs.dll/article?AID=/20060424/FREE/60417021/1008
"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 range...at 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."
See 1000q: mk3 jetta/passat new owner checklist to see a detailed list of common problems and immediate maintenance these cars need, below is a summary.
a3/b4 VW refers to the 1996 - 1999 jetta (a3) or 1996-1997 passat (b4). These are usually the least expensive cars to buy because of age, mileage, and standard features. These are the earliest turbocharged VW diesels sold in the US. They feature the 1.9L 4 cylinder 90hp/149 ft-lbs torque engine, manual transmission available. All cars are front wheel drive. Jetta is 4 door sedan only, passat was available as a station wagon or sedan. Estimated MPG 35-38 city/46-50 hwy. It's possible to obtain the greatest mileage with the mk3 jetta compared to later cars due to their light weight. The trade off of lighter weight is less luxury and safety features.
See 1000q: VW mk3, m4, mk5 generation differences for a detailed list of differences between generations. For a full list of "how to" maintenance on these cars, refer to 1000q: mk3 "how to" index. Below is a quick reference.
Pros:
Cons:
Common problem areas:
Major model year changes:
For a full list of "how to" maintenance on these cars, refer to 1000q: mk3 "how to" index.
For more detailed technical specs, maintenance intervals, and model year
changes
click here for 1997-early 1999 a3 jetta
click here for 1996-1997 b4 passat
See 1000q: mk4 jetta/new beetle/golf new owner checklist to see a detailed list of common problems and immediate maintenance these cars need, below is a summary.
a4/b5 refers to the 1999.5-2005 Jetta, 1998-2006 New Beetle, 2004-2005 Passat, and 1999-2006 golf. These are the most common TDI because more cars were imported to North America than other generations. The 1999.5-2003 engine is now rated at 90hp/155 ft-lbs torque because of a newer turbo design which gives better low end power. All Passat have 2.0 8v engines with 134 hp/247 ft-lbs torque. 2004+ cars feature "pumpe duse" engine rated at 100hp/177 ft lbs. Both manual and automatic transmissions are available but the auto transmission gives lower fuel mileage. All cars are front wheel drive. Jetta available as station wagon after 2002, Passat wagon available after 2004 (auto trans only with Passat). MPG est. 35-42 city/45-50 hwy. Later cars after 2002 have 80,000 and 100,000 mile timing belts that can be retrofitted to earlier mk4 cars.
Also see 1000q: pumpe duse vs direct injection
to see some mechanical differences between the pumpe duse and non pumpe duse
cars. For a full list of "how to" maintenance on these cars, refer to 1000q:
mk4 "how to" index and 1000q:
mk4 how to index for pumpe duse cars. Below is a quick reference.
Pros:
Cons:
Common problem areas:
Major model year changes:
For a full list of "how to" maintenance on these cars, refer to 1000q: mk4 "how to" index and 1000q: mk4 how to index for pumpe duse cars.
For more detailed technical specs, maintenance intervals, and model year
changes,
click here for 1998-2003
new beetle
click here for 2004-2006 new
beetle (pumpe duse)
click here for 1998-2003 a4 golf
click here for 2004-2006 a4
golf (pumpe duse)
click here for early
1999-2003 a4 jetta
click here for 2004-early
2005 generation a4 jetta (pumpe duse)
click here for 2004-2005 b5
passat (pumpe duse)
See 1000q: 2009 VW Jetta diesel buyer's checklist and guide for detailed dealer invoice price, MSRP, options, and other buying tips.
a5 refers to the late 2005-2006 and 2009 and up jetta. These 4 door sedans are among the best condition cars because they are all only a few years old but are generally the most expensive. 2005.5-2006 TDI use the pumpe duse engines, 2009+ use the common rail engines. See 1000q: pump duse and common rail for more technical descriptions of the engines. They also have the option of the DSG automatically shifting manual transmission, not to be confused with a conventional automatic transmission. Introduction of the independent rear suspension on jetta on all models. Due to emissions, not available for model year 2007 or 2008 (some cars were built in early 2007 and sold as model year 2006). All early production cars may potentially be equipped with a defective clutch, the dealer should replace it according to this technical service bulletin.
See 1000q: VW mk3, m4, mk5 generation differences for a more detailed list of differences between generations.
Pros:
Cons:
For more detailed technical specs, maintenance intervals, and model year
changes,
click here for late
2005-2006 a5 jetta
Mercedes turbodiesel cars include 1984-87 mercedes 300sd, 1990-1995 300D nonturbo diesel, 1996-1997 E300D nonturbo diesel, 1998-1999 E300 turbodiesel, 2002-2006 320 CDI turbodiesel and the new 2007+ 320 bluetec turbodiesel.
This summary will concentrate on the 2002-2006 320 CDI and
2007
320 bluetec. The 2002-2006 320 CDI (common rail diesel injection) features an inline 6 cylinder turbodiesel iron engine featuring 201hp/369 ft-lbs torque and a 5 speed auto transmission. The 2007 320
bluetec features a new lighter v6 aluminum turbodiesel rated at 211hp/398 ft-lbs torque with 7 speed auto transmission and better "bluetec" emission equipment. Both are sedan only and rear wheel drive.
Pros:
Cons:
To dispel one of the biggest myths about biodiesel, it is not the same as used
grease or straight veggie oil. That would be like saying that gasoline is
the same as crude oil. It is a fuel for diesels, refined from oils or
grease. It is one of the most commonly used alternative fuels that will, in my opinion, gain
much more widespread use in the future. Note that I did not say that it was a
super fuel from the future. In other words, it is not a magic bullet that will solve all of the world's
fuel crisis. Having said that, as diesels
become more common again, biodiesel will also become more popular, especially once people learn about the advantages of using biodiesel.
Biodiesel is basically a fuel made from refined and processed oil, fat, or used waste grease. It is cleaner burning than petrol diesel, normally domestically grown and processed, and a 100% renewable fuel. It can be used in modern diesel engines and oil-fired home heating systems with little or no modifications. It is also biodegradable, less toxic than table salt, and with greatly reduced odor and emissions compared to diesel fuel. From an environmental perspective, it is greener than petrol diesel. From
a cost perspective, it can be cheaper than petrol diesel. From an engineering perspective, it is better for the
engine and injection pump lubrication. From a geopolitical and national security perspective, it is domestically grown and produced.
I expand upon these points in 1000 answered questions: biodiesel.
Unlike veggie oil, it's viscosity is much closer to that of diesel fuel, reducing the chance of stressing the mechanical fuel pumps, and requires no modification to a modern diesel car. Unlike a grease car that runs on veggie oil, it does not require modification to the car or require the car to be started and stopped on diesel fuel to flush the fuel lines. If the fuel lines are not flushed prior to shut down, a grease car may not be able to start with veggie in the fuel lines. The only negative of biodiesel is that it gels at a higher temperature than diesel. Diesel fuel begins to gel at -20oF, 100% biodiesel without winterization begins to gel anywhere from 14oF to 50oF depending on its source. Biodiesel available at retail fuel pumps, usually 20% biodiesel 80% petroldiesel does not suffer from these problems because it has winterization elements added.
Biodiesel is also better for a diesel engine. There is no question that it lubricates the engine better than petrol diesel and has a cleansing effect upon the fuel system, cleaning out any diesel build up. Because of the new ultra low sulfur fuel used in the US and Europe, using just 2% biodiesel will lubricate the engine and fuel pumps very well. There is debate as to biodiesel causing buildup on the fuel injectors but you should use fuel injector cleaner once a year anyways. Because the longevity of a well maintained diesel engine is already so long, the added lubrication will help guarantee a long engine lifespan.
Another reason or its popularity is that it can be inexpensively made by the user. It's cost may be anywhere from 25 cents/gallon to $1/gallon if you collect used grease from local restaurants that normally have to pay to have their grease removed and use this to make biodiesel at home. Please note that biodiesel making materials, processes, and equipment may be regulated by fire codes and is a potentially hazardous activity so always follow safe and prudent operating procedures. Always comply with any local, state, or federal regulations regarding your biodiesel making materials, processes, equipment, or biodiesel use.
For more information on making biodiesel at home, click here for 1000 answered questions: Intro to making biodiesel
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