Automotive/Honda vs. VW

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Expert: - 6/4/2008


Question
Sir,

Maybe I need to rephrase my question.
I am currently looking for a car, that gets good gas mileage, for under $5000.  I was wondering which car, Honda Civic or VW Jetta, would be better.  The Civic drives on regular gas and gets about 30 mpg.  The Jetta drives on diesel and gets about 40 mpg.  However, I have no idea how diesel compares with regular, or how VW compares with Honda.  Can you use your broad knowledge of various cars and knowledge of diesel engines to help me make an informed decision?  
Thank you.

Steven

Answer
The very general answer is that (1) there is more energy in a given volume of Diesel fuel than there is in an equivalent volume of gasoline and (2) the Diesel process is significantly more efficient than is the Otto cycle process.  Inasmuch as the Diesel process is an excess-air process, that efficiency is even better still if the engine is turbocharged, as most Diesels these days are.  

With those concepts in mind, a Diesel-powered vehicle will go more miles (or km) on less fuel, other things being equal, than will a gasoline engine.  This would equate to less operating cost.  The only negative in the ledger is the higher initial cost for a Diesel, however, those extra dollars are buying an engine which is inherently heavy-duty by virtue of its design to accommodate the high-compression stresses of the Diesel process.

My personal vote?  I have been driving my venerable Mercedes Diesel for over a year now, and I am sold!  Even though Diesel fuel presently is higher-priced than gasoline, my fuel bills have fallen substantially, even as my miles driven have increased over the past year.  I get between three and four weeks of suburban driving, driven five to six days a week, up to fifteen miles per one-way trip.  Specifically, I get a fairly regular 25 miles per imperial gallon (4.59 litres) in city/suburban morning rush-hour driving, and that from a pretty nimble and also very solid 24-year-old car.

Again, the above is general, and my own vote reflects my own personal experience.  You would do well to talk with both Honda and Jetta owners to get some ideas attuned tot he choices you are considering.  Reliability and service issues are important, whichever you might choose.

Take some test drives!  Happy hunting ... EGK

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Ernest (Ernie) Kenward

Expertise

The challenges I most enjoy are thoughtful technical questions of a trouble-shooting nature in both electrical, power electronic and mechanical systems, mainly automotive but also machine control and small-machine PLC applications. Please note, however, that I am NOT a walking shop manual! I DO, however, make it a point to have those manuals and other service literature for those vehicles I DO own, and highly recommend that anyone serious about maintenance or modification of their vehicles do the same; MOST of your answers WILL be found there. For that matter, I do NOT go out of my way to acquire shop manuals for any vehicle I do NOT own! That being the case, any general query to me along the lines of "What is the meaning of this code read from the ECU of my 2015 XYZ?" or "Where is the fuse for the windshield washer pump found?" (try your car's electrical distribution panel for a start!) will not go far. What I do offer is a pretty good collection of literature, insights and hands-on experience with 1950s to 1980's Ford products (plus a developing database of information and practice with the Mercedes diesel cars), along with an engineering perspective and the ability to design and implement custom control, electrical and mechanical subsystems for vehicles. For that reason, I am happy to make my thoughts and efforts available to those who are of like mind and/or are seriously making a point of learning about their vehicles. Use the Opportunity to Learn!

Experience

A key skill in my work and hobby pursuits both is STRATEGIC TROUBLESHOOTING. I am a senior instructor in Electrical Engineering Technology at a leading Canadian polytechnic, my areas being Electrical Power and Industrial Control, electrical and electronics design and manufacturing, and AutoCAD and related CAD/CAE software - plus equipment problem-solving and new equipment design and prototyping. Hobby-wise, I have 30-plus years of experience in auto restoration, mostly in electrical and mechanical systems. Ongoing projects include a 1959 Edsel Corsair, my 1978 Ford E250 class-B motorhome conversion, and the care and upkeep of my Mercedes 300CD. My vehicles become engineering test beds for electrical and mechanical upgrades as ideas present themselves. This includes the design and production of circuit boards to restore or enhance features for which no OEM replacement parts are obtainable, or where better specifications or reliability can be had via newer concepts. Regarding the E250 RV conversion, I designed and continue to revise a custom power distribution system, managed by a Programmable Controller (PLC); this has made most revisions as easy as uploading new firmware as I develop it. The "mini" PLC is a powerful device for custom automotive control systems. One good example (there are many) would be the Moeller "Easy Relay"; these offer a wealth of control, monitoring and variable-and-status display options for such projects. A good example project which has worked well is that one for my RV noted above, which has been on the job - revised in firmware only - for a decade now. It is a load management and charging control system to avoid the sulfation-induced early failure that often befalls deep-cycle batteries used in RV power applications. The battery installed in 2003 lasted long enough to more tnan pay for the PLC that contributed to its longer life ... and the PLC will be there for the next battery as well!

Organizations
IEEE - senior member ... past WCC Student Activities; SME - senior member ... past chair, greater Vancouver chapter chair 318; Edsel Owners' Club - have served in various capacities on chapter executive during seventies; have been Power and Driveline resource on the Edsel Owners' Club "E-team" for more than a decade.

Education/Credentials
Graduate of UBC

Awards and Honors
Certificates of appreciation from IEEE and SME for work in student and chapter activities

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