Hi all

On this bright morning I thought to ask you here on r.c.m. if any of
you know what makes the difference for a diesel car between very good
fuel consumption and just good fuel consumption.

The punchline is - where is the extra 30+% fuel consumption going in a
"modern" car?

UK / Europe factor - every car mentioned has manual ("stick-shift") transmission - five-speed or six-speed.

For nine years, I had a car which reached 20 years of age and went
everywhere, every day, at 63MPG (Imperial 10pint gallon (4.536L); 50.4
miles per US Gallon; 22.2km-per-Litre). With plenty of power -
delight to drive. Turbo spun-up and it surged forward no need for
gear changes.

Even a vibrating rattly tiny Fiat supposed to do 70MPG (Imperial) did
only 55MPG.

My current car mid-range (European style - probably very compact by US standards) is super luxurious, has a six-speed gearbox, goodly amount
of power - no hills steep enough to keep speed below 70MPH when
cleaning out the engine with sustained accelerator to floor - but
"only" 48MPG (38.4miles per US gallon; 17km per Litre)

A few years ago I was told 60+MPG "is a thing of the past" "with new
emission reg.s" (!!).

The 63MPG car, built in late 1990's, was turbo-diesel, fly-by-wire
diesel injection, probably no filters or anything on the exhaust side
of the engine.
At 63MPG, it cannot have been throwing anything / much out of the
exhaust part-combusted - else it wouldn't be doing 63MPG...
It weighed 1~1/2tonnes - heavy for a smallish compact car.
However, whatever that weight was, it seemed to be involved in
something which nett left you advantaged.
That was 1.9Litres - quite large by UK / Europe standards - where my
more modern car is something like 1.6Litres capacity.
It sounded like a tractor, for sure, when at idle.

That car, the 63MPG car, was Spanish built and badged from the
Volkswagen stable. Someone told me it had the engine from the earlier
VW Golf GTD (turbo diesel performance model). When that was no longer
the new premium model.

So yes, if you could be happy with

a car which sounded like a tractor, you warmed it up slowly to be kind
to the environment, didn't mind that the heaters only worked after
about 3 miles of driving (if you aren't burning much fuel you are not
producing much heat, plus you have a big heavy engine to warm up)

then you got a totally delightful car.

But that fuel consumption... 63MPG (Imperial)
That is the possible.

Where is that extra 30+% fuel going in a "modern" car ???????

The 63MPG (Imperial) shows what is needed to do the job with a
"straight diesel" car. So you can use that as a reference and ask -
for a "modern" car, where is that extra 30+% of "un-accounted-for"
fuel going ???????

I would be very very interested to know.
I've had that question in my mind for since I found I couldn't
like-for-like replace the wonderful VW-family car.

Regards,
Rich Smith

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