Two Part Answer here - Part one is a bit of a rant, Part two is something worth reading regarding diesel v/s petrol.
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I hate it that they ripped the Vectra for this azn 525i attempt.
Mind you though, I guess;
-The V6 Veccys were pretty dear and you were still only getting a Holden badge which, unfortunately, drew a lot of stereotypes which would say things like "but the Commodore's got a bigger engine" and "what's European?..is that where that Hitler guy lives" etc.
-Anyone who looked anywhere on the internet would see heaps of crap on the Vec from both that prat Clarkson & disgruntled owners who tried to run the Vec B like a cheap Daihatsu (91 RON, not serviced regularly or serviced poorly by Holden mechanics not knowing much about the car despite the fact it was made here for a number of years)
Not to Underestimate the mental capacity of our culture, but I guess the Vectra wasn't the right car for the "All Aussie" car maker to sell. The average Holden buyer couldn't justify the spend (for the V6 Vec Cs at least) when they could have more car for less in the commodore. Those that really wanted European would've probably been able to spend the extra 10-20k to get something like an Audi A4 Quattro or a 330i, and then they weren't buying a Holden badge.
In my honest opinion cars like the Vectra C (and perhaps the Tigra as well) would've done better if they were sold here with the Opel badge by an Opel or just generic 'GM' dealer. (Much like what Skoda is starting to do).
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To return somewhat to the Topic, a Diesel epica is all well and good, but it's getting to the point where the difference in the price between Petrol and Diesel is enough to more then offset any comsumption difference.
Put it this way - my 1998 1998cc Vec B CD does 7.8L/100km when I use 95 RON premium unleaded. (Mind you it uses a Cone filter and decent spark plugs so I'm guessing I have around 104kW of power (stock is 100). (Those two mods cost me a grand total of around $80.)
The claimed output on the diesel Epica is 110kW for 7.6/100km
I filled my car today, and I paid $1.45 for Caltex Vortex (hooray for living in QLD). Diesel was selling at the pump next to me for $1.72. The difference in price means that over the difference of one 60L tank, you'll pay $16.20 more for Diesel.
One 60L tank will theoretically get me 769Km, and one 60L tank will get the Epica 789Km. That's 20 extra Kilometers for $16.20. While driving those 20 kilometers, my 20th century technology Vec B will consume 1.56L of fuel, which to me is worth $2.26.
So summing up, My petrol Vectra B with $80 worth of engine mods will do 789Km for $13.94 less then it costs a new diesel Epica if prices stay around the same. Most predictions argue that the gap between diesel and petrol will grow as demand for the heavier distillate increases.
As an afterthought, let's not forget the other diesel things to know
-More low down torque, but overall less performance orientated
-Dirtier, more emissions
-Harder to start in cold areas; Start requires glow plug
-Reasonably agricultural in soundbyte
-stigma attached to them in Australia at least (as you can see from my stereotypical remarks above)
That's all for now...