[Vwdiesel] Gas vs diesel hybrid

[David Cook]

William-

Interesting thoughts.  I actually saw a magazine at
Wal-Mart (I think it was Popular Mechanics) that had
something about 100 MPG cars on the cover.  I stopped
and read the article.

PM advocated the use of a diesel-hybrid auto as one of
the keys to a very high mileage vehicle.  They did
mention a couple VW vehicles, including the 1L car
during the discussion of diesels.

Here are my thoughts on this:

Those old engines were not necessarily intended to be
driven in that manner.  So, when on short trips, you
could say they were being driven outside their design
ability.

I would guess that first, in general, engines are
going to last longer than those older ones, just
because of improvements over the years.  Second, I
would imagine that a diesel hybrid engine would have
to be purpose built for that, not a whole lot of the
"hard" parts would be reused.  (Just a guess there.) 
Because of this, I am real sure that the heating
cycles would have to be considered when building the
engine.

An interesting thing the article mentioned was a guy
who sometimes achieves over 100 MPGs in his hybrid
Toyota.  He added solar panels to the roof to help
charge the battery so the engine doesn't have to run
as much.  Don't know that I'd do it, but it was a
pretty clever idea none the less.

David

--- William J Toensing <toensing at wildblue.net> wrote:

> I could & hope I am wrong, but I think gas engine
> hybrids are better than diesels under the normal
> conditions most cars are exposed to, namely short
> start & stop driving, based on my experience around
> 25 years ago. My first diesel was a 1979 Rabbit,
> which was bought new, but went to my X wife in a
> divorce. It had around 30,000 miles on it when this
> happened. My second diesel was a 1983 Nissan Sentra
> diesel which had about 51,000 miles on it when I
> sold it & at that time I suspected the head gasket
> was leaking as evidenced by a black scum in heater
> expansion tank, running warmer than normal, &
> periodically having to add water to the cooling
> system. My next diesel was a 1985 Mazda 626. At
> 50,000 miles the head gasket blew leaving clouds of
> black smoke behind. Mazda paid for the repairs under
> the Calif. emissions warranty, then 10 years or
> 100,000 miles. At 70,000 miles, the head gasket 
> blew again, this time, causing overheating. Because
> I was using synthetic oil, the engine did not seize
> but got so hot the valve springs lost their temper &
> the engine stopped. However, the engine got so hot,
> the temper in the block was destroyed & the engine
> had to be replaced. This time, because of the
> mileage, I had to pay 50% of the engine replacement
> & Mazda paid the other half because only 20,000
> miles elapsed between the first head gasket
> replacement. I also found out the Mazda used stretch
> bolts which Mazda did not recommend re torque.
> However, this time I had the head re torqued & the
> engine lasted another 127,000 miles when it
> overheated because a thermostat hose blew because I
> did not replace it along with other hoses, because I
> didn't know it was there. 
> I have had a long term interest in diesels ever
> since I saw my first Mercedes Benz diesel back in
> the early '60s. When GM came out with the converted
> gas to diesel Olds 350, the engine that gave diesel
> a bad name in the USA, I would ask owners of these
> GM diesels what their experience was. I found a
> pattern that when the engine was used for mostly
> local driving with occasional trips, the head
> gaskets would blow  at around 20,000 miles. The
> weakness, I understand, was due to only 4 head bolts
> per cylinder. That frequent heating & cooling along
> with the high diesel compression, would cause the
> head bolts to stretch, causing eventual head gasket
> failure. However, I found a few Olds GM 350 diesel
> owners that were claiming 250,000 to 300,000 miles
> on these engines with no problems. However, the
> response I got from those owners was they would
> drive these cars from 75 to 300 mile trips for most
> part rather than trips of 10 miles or less.
> Since a hybrid engine frequently cycles off & on, I
> wonder, based on the above, how well a diesel engine
> would do in this environment?
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David Cook
Red '86 Cabriolet Diesel Powered
Red '90 g60 Corrado 
Brown and White '78 Westy Campmobile "Bear"
and others in various states of disrepair
Pictures here: community.webshots.com/user/superdave5599

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