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Re: Diesel OK?

Posted by Steve Smith on Mar 29, 2018; 11:03pm
URL: http://friam.383.s1.nabble.com/Diesel-OK-tp7591363p7591364.html

Owen -

I would generally recommend diesel but have a few caveats for you:

First the pros:

  1. Higher MPG
    1. higher energy density per liter of fuel
    2. higher compression engine (more efficient)
    3. leaner combustion at idle or under low load
    4. better emmisions *except* particulates
    5. Usually are coupled with a turbo (they benefit more than petrol?)
  2. Longer engine life
    1. design/construction intention?
    2. better cylinder lubrication?
  3. HIgher power/weight ratio.
  4. Longer range (see pro: 1 above)
  5. Come the Apocalypse you can burn Vegetable (used or pressed from myriad growing things) Oil.
  6. Come the Apocalypse you can (also) burn motor oil drained (and highly filtered) out of the crankcase of petrol vehicles which are abandoned when they can't get more fuel.

I have only owned diesel tractors and full size trucks but most of the above probably still applies

The cons:

  1. Diesel is a bit messier/smellier (not a big deal with truck or tractor)
  2. Diesel fuel is more expensive than Petrol at the pump, that didn't used to be the case, I think it is based on demand-side economics since I think yield per barrel is higher and cost of refinement lower.
  3. Diesel pumps are very slightly less available... I occasionally pull in to a station without it or find only one bay with diesel...   Pricing seems to be more consistent.  The ubiquitous use in OTR trucks says you will never be far from a diesel pump.
  4. Diesel maintenance and repair is higher than petrol. 
    1. Air filters are more frequently changed (or cleaned)
    2. Fuel filters are more frequently changed.
    3. Oil volumes (my 5.9L Diesel engine uses 10 quarts) are greater, etc... but all this factors out nicely when you consider Pro:2
    4. Engine Complexity
      1. Turbo adds complexity
      2. lack of ignition system reduces complexity (a pro, not a con)
      3. Older diesels were mechanical injection, eliminating most electronics (not relevant to you).
  5. Cold Starting demands more (usually dual) batteries, leading to one more point of failure and/or expense...  a block heater with a battery trickle charge to plug into if you are planning to leave early on a cold morning is a good idea.

I seem to remember that Bruce and Ruth bought a diesel Jeep SUV and traded it in within the year because they were having maintenance problems associated with not driving it at highway speeds very often.   I don't know about this really since heavy equipment has an even sillier duty cycle than their commute nature did.  Probably a design issue that *might not* be one for the vehicles you are considering.

I get the impression that most passenger diesels shadow their heavy equipment and truck parts with higher mpg, longer lifespans, but higher maintenance costs...   but not in the same extreme.   I know of VW Golf TDI owners who get as good of MPG as my tiny 2 seater Honda Insight Hybrid (~50).

The Germans (BMW, Mercedes, VW) have a lot of experience with Diesels.

They all seem to have scandals around cheating on emissions testing (not just VW).

My sensibilities would recommend a diesel-electric plug-in hybrid since you probably have the cash to invest and trust it to pay back (mostly) in operating cost and good karma.  I don't think there are any of these outside of the concept showrooms yet though.  Almost surely not a BMW Wagon...

- Steve


On 3/29/18 4:13 PM, Owen Densmore wrote:
We're getting a new BMW station wagon and they recommend getting diesel over your basic gasoline. Better milage and more reliable engine.

I'm wondering what that's like here in the USA. In Italy it was the usual fuel but I'm wondering just how widespread diesel is here? And if there are other annoyances like only one diesel pump which can have a crowd?

   -- Owen


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FRIAM-COMIC http://friam-comic.blogspot.com/ by Dr. Strangelove
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