@HumbleMechanic and @JavierMota talk diesels: Pros/Cons

Discussion in 'Diesel powered automobiles' started by xcel, Jul 9, 2014.

  1. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi All:

    Listen to it in the background. Good stuff from two friends...


  2. tribosessive

    tribosessive Well-Known Member

    I just listened. If the fuel filter has to be replaced every 20k miles, that is often for me. It is highly doubtful, what with high pressure fuel delivery systems, but it would be nice if this procedure could be DIY.

    I am also excited about the possibilities with diesel hybrids. xcel, I am wondering how soon this will happen. Charles says it's when, not if.

    What is clear to me, is that mega durability makes diesel a winner, for my application. With the knowledge that the next Prius will get 70+ mpg, and the reports that hybrid batteries are lasting for a long time, I will have an interesting decision to make in my next car purchase.
  3. RedylC94

    RedylC94 Well-Known Member

    That's debatable, because gasoline engines are more durable that antiquated conventional wisdom would have us believe---assuming they're not defective or abused. I haven't been able to wear out my gasoline engine in 603K miles. Would a diesel have done significantly better? It doesn't matter, if the engine is going to outlast the body (or the owner) anyway.
  4. tribosessive

    tribosessive Well-Known Member

    First, thank you for your reply. Second, I applaud you, redylC94, for your accomplishment. It would seem that you and your GLC are unique. There has to be something going on here. Maybe it's your driving style or your maintenance plan. Maybe it's your self-discipline, which you have obviously sustained for all these years. Your points are indeed food for thought. What this means is that I will now consider a Golf Sportwagen with TSI, as well as TDI.

    Any additional comments on what you have done, specifically, to get over 600k, no doubt fuel efficient, miles out of your 1981 Mazda GLC, would be greatly appreciated.
  5. RedylC94

    RedylC94 Well-Known Member

    Thanks. I'll have time to reply tomorrow afternoon, I hope.
  6. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    While it's nothing close to 600, my Civic went 200,000 miles with nothing more than basic oil changes for engine maintenance. Other parts needed repairs, but I never touched the engine itself. (Main events were CV joints, exhaust in a couple places, radiator leak, clutch hydraulics leak)
  7. RedylC94

    RedylC94 Well-Known Member


    I'm back.

    I hope you won't be disappointed to learn that I can't reveal any magic formula for gasoline engine longevity. It helps greatly to be lucky enough to chose a model that doesn't have major design weaknesses, and a sample with no major manufacturing defects.

    Otherwise, I've mostly just paid attention to basics most people looking at this site probably already know and practice. For example, stuff like
    1) Use respectable fluids and filters (which need not be pricey ones, and need not be changed over-frequently);
    2) As much as possible, avoid trips too short to fully warm up the engine (Walk or use your bicycle for light-duty local errands!);
    3) Fix small problems before they become big problems;
    4) Stay away from high RPM when not necessary;
    5) Don't try to keep up with the speeders on the Interstates.

    As a child and teenager, I was impressed by occasional stories of engines going trouble-free beyond 100K or even 200K. Even more amazing, some of those were in gasoline medium-duty trucks in tough service. By now, such mileages are commonplace, and nearly everybody seems to know somebody who has taken a car or truck much farther. Then there are the famous examples---the Wisconsin Saab that went over a million miles, the Long Island Volvo that was way past three million when last heard from, the Prius cabs in Vancouver, the '56 Caddy cab in Chicago, et al.)

    Many different brands of vehicles have pulled off high mileages. Since you mention VW---my brother's gasoline-burning Jetta was still running as well as ever and burning very little oil (although it leaked oil, thanks to the dealership) when he gave up on it somewhere beyond 300K (estimated, because the odometer died much earlier) due to bad shift linkage. Now he has an Avalon that's in the same ballpark already, and also still running like new.

    As for my Mazda's engine in particular, there's not much about it that was especially novel in 1980, unless you count then-new friction-reducing measures like lighter valve springs, low-tension piston rings, and aluminum rocker arms. Having a proper chain instead of a rubber band to drive the camshaft hasn't hurt. When I bought the car, I decided to prove wrong all the old-timers who claimed small car engines wouldn't last. By now, it has made my point by outliving most of those old-timers.

    In hindsight, the worst mistake I've made with this engine was a piece of ill-advised tinkering, restricting flow in a seemingly needless coolant bypass hose. Bad idea!

    Sorry to ramble. The main point is, there's no great trick to racking up high mileage on an ordinary gasoline engine, if you're a little bit lucky and reasonably careful.
    Last edited: Jul 10, 2014
  8. seftonm

    seftonm Veteran Staff Member

    I don't think the durability of a diesel will be much of an advantage unless a person is planning on putting on lots of miles doing heavy towing or something like that. Gasoline engines can last a long time too.
  9. tribosessive

    tribosessive Well-Known Member

    I really enjoyed reading your post, RedylC94. You explained it quite nicely. Thank you.
  10. WriConsult

    WriConsult Super Moderator

    Agreed, almost all engines (as well as the entire Prius drivetrain) are good for 200k miles and more nowadays, without major repairs. The fact that diesels are typically good for 600k miles and gassers are good for 300k isn't very relevant when your typical VW vehicle is starting to fall apart by 300k anyway.

    To me it comes down to this:
    1. Hybrids have a distinct advantage in city driving because of engine shutdown and regenerative braking, and gain an edge for people who do more local than rural driving. That said, the non-SUV ones still tend to get excellent highway mileage due to aerodynamics and right-sized engines. Most of the popular hybrids (Toyota and Ford) also have exemplary reliability, significantly better than the diesel offerings (meaning VW, in the affordable end of the market). I think the lower priced hybrids still provide a better ownership-cost proposition than the lower priced diesels.

    2. Diesels have the FE edge for people who do mostly highway driving. But (here's "that said" again...) they idle 3-4x more efficiently than non-hybrid gassers and can still return excellent city mpg in the right hands. Also, my experience is that while hybrids require a pretty light touch for maximum mpg, you can put your right foot into a diesel a lot more and still get good economy. In other words, having a lead foot does a lot less harm in a diesel than in a hybrid. And finally, while they may not have appliance-like reliability, VWs also don't have an appliance-like driving experience. Fingers crossed to see if the Cruze finally brings us the benefits of a diesel with lower maintenance costs than VW.

    So if you do lots of short trips or have a moderate length commute in typical American suburbia, and want to maximize fuel economy and keep your costs down, hybrids are pretty appealing. If you have a long commute or do lots of road trips, or want a more exciting driving experience, possibly while maintaining a more aggressive driving style, diesel may be better for you. Diesels are also better if you want to avoid negative attention from irrational Prius-haters.
    Last edited: Jul 11, 2014
  11. tribosessive

    tribosessive Well-Known Member

    Thanks Wri. Next generation Prius at 70mpg will be very tempting. PriusV should be high. I need cargo area.
  12. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Dan:

    Excellent recap.

  13. phoebeisis

    phoebeisis Well-Known Member

    Yeah diesel durability-implying a spark motor will "break"
    Just not true.
    Besides it is the fuel systems on a TD that seem to fail early-and expensively.

    My 1998 GM -227,000 miles-still gets 21mpg hy
    And this is just a older plain jane GM -not a better QC more recent vintage car-or one from a manufacturer with historically better QC

    Like Redy says- modern spark motors rarely break before the vehicles are ready for the junk yard
    Heck the AT breaks on a 16 yo vehicle-you not infrequently are better off buying a "newer" $6000 used car rather than putting $3000 into the repair(depends on what other things you have repaired recently-AC CV radiator water pump joints etc-things that always wear out
  14. tribosessive

    tribosessive Well-Known Member

    As stated many times, I am a delivery driver-subcontractor. The deliveries are 1-250#, envelopes to standard sized pallets. Most deliveries are in the Bay Area hub, San Jose, Oakland, San Francisco. My circumstances are rare.

    However when my numbers are crunched, the factors everyone must consider, involving application, length of ownership,...ie cost of operating the vehicle are magnified.

    I spend $1600. per month on fuel. At 30 mpg vs 60+mpg for a hybrid, and almost that for a TDI, that cuts the fuel costs in half. We are talking about $800. month in savings, enough to cover a car payment, and then some.

    I need to study emissions systems regarding technology, reliability, and maintenance costs. Passing smog checks and extending the life of a vehicle is the goal. I know, for example, that Mazda has developed innovative technologies in emissions systems for their SkyActiv vehicles. I am anxious as to whether this will happen for SkyActivD in NA. VW/Audi TDI is very interesting also

    . Maybe there will be an HRV hybrid. LOL.
    Last edited: Jul 13, 2014

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