The diesel vs petrol economy debate

I always price a car based on Total Cost of Ownership. To focus on just one particular item on the list of expenditure is like something the New Labour government used to do.
 
iaind said:
Oh lord do we really need another diesel thread, these only ever go one way.

Anyway, on a run from Exeter to essex down the 303 I'd see 52ish from the Mondeo and 35 from the Saab. Doing the same trip on saturday in the Honda and I reckon it would be about 40.

In terms of 'like for like' - how do you define that? Bhp? Peak torque? 0-60? Purchase price?

The closest I can think of is the Mondeo vs the Accord - similar performance, similar bhp, similar size and abount 10mpg difference in any given situation
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Which was petrol which was diesel?
 
2001 Astra 1.7dti - approx 50MPG on my daily commute

1997 Astra 1.6 16v - approx 30MPG on my daily commute.

I try to use the diesel as much as possible, but the Mrs hates driving the older astra.

No i am not an astra fanboy, in fact quite the opposite, i hate them both but circumstance dictated the vehicles rather than choice.

I am not a petrolhead at all, cars are cars to me, but given the choice i would take the diesel every time.
 
Used a E60 530d, E60 530i and now an F10 530d (last thursday) to jaunt up to Bracknell, some 80 miles of motoroway and DC roads.

E60 530d = 47mpg
E60 530i = 39mpg
F10 530d = 47mpg

All were driven slightly differently as no two trips are the same but all were with cruise set to 75mph for the majority of the journey.
 
Managed 53mpg from a 2.0TDCI S-Max on a long trip, and that was doing at least the speed limit

They're economical on longer runs but as soon as you get them into more urban situations the lines seem to blur a little
 
NathanE said:
I always price a car based on Total Cost of Ownership. To focus on just one particular item on the list of expenditure is like something the New Labour government used to do.
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I'm quite interested in this debate because I have a friend who is a die hard diesel fan-boy. Every discussion about cars always comes down to him telling me diesels are better "because they are more efficient and just as fast as petrols". Im beginning to lose hope because nothing I say can convince him otherwise. I tried explaining about the more favourable driving characteristics of petrols but he disregarded them as "an immeasurable subjective factor", which is false. You can measure it.

"You do you prefer driving petrols to diesels?"
"Yes".

Done. Measured. All to no avail. "But diesels are so much better, having that much torque makes driving on the motorway so much better", blah blah blah. So does having an automatic. Sigh.

Anyway, I decided to run a quick unscientific test using the quoted figures of the coupé 325x on BMWs website. Using the combined MPG figures and this fuel calculator, over 10,000 miles per year, it turns out the diesel would save you a whopping £229.17 a year in fuel! (With petrol at 114.9ppl and diesel at 115.9ppl)

So, you save just over two hundred quid a year. But, considering that the purchase difference between the 325d and the 325i from new is £1300 in favour of the petrol, it would take (if my rough calculations are correct) 5.6 years before you broke even on fuel costs if you bought the new diesel over the petrol.

Is it really worth it, considering that the petrol is quicker and more powerful, will be less noisy, probably incur lower service costs and wont smell? Given this evidence, who would really buy the diesel over the petrol?

Im aware I could have made a glaring error in some of my calculations as I was just working this out quickly. Feel free to check and criticise my figures, it just surprised me that it seems at first glance the diesel is actually the more expensive option to run from new.
 
OK, will that blow all my calculations out of the water when applied to company cars then?

Also, I'd like to say, Im not "anti" diesel. It isn't that one or the other is better; they are jsut different.

The friend Im talking about really annoys me because he looks at me smugly and tries to discredit my arguments by saying that "you just hate diesels, all you care about is going fast" because I argue with passion and get heated when he spouts more made up pro-diesel propaganda at me. Its evident that if there is any fuel fanboy, its him and his complete inability to realise the advanatages of anything that isn't diesel powered. If he wasn't so busy masturbating over MPG/torque figures all the time he would have heard me say several times that my next car will probably be a diesel.

He once told me that petrol fuel would soon be rendered obsolete. I'm still laughing at that one.
 
From my eyes at least, they both serve a purpose, but blindly saying that diesels aren't fun, or petrols can't be economical is just as daft either way.

For my usage patterns in the last 12 months, nothing would have come close to my 330d (or a similar car, large diesel engined saloon). It's smooth, refined, great to sit in on the motorway, and returns sensible consumption, and manages all this whilst being a great drive, and something in which I can have fun (due to the handling and driver feedback) should the mood take me.

Make no mistake though, should I be in a position to run an out and out sports car, with no consideration to fuel consumption, I'd be the first person to take a large petrol engined vehicle (preferably with a soft-top and RWD), but as an all rounder, a workhorse, a do-it-all, nothing really ticks the boxes as well as a decent diesel engine.

I actually loathe driving my LCR these days. Granted I plant my foot, and it makes a decent noise and tries to flee to the horizon, but in every other way it is more laborious than it is useful. Loud, brash, un-dynamic in its drive, AND it uses fuel like it's a cheap commodity. In the last week, I used my 330d for 5 days, and my LCR for 2. The 330d has used about £15's worth of fuel, the LCR has used almost £40.
 
paradigm said:
I assume he means Company Car Tax (BIC?).
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More than likely (it's Benefit in Kind or BIK). For those that don't know, basically the CO2 emissions dictate the percentage of the list price on which you pay income tax.

Typically, the diesel equivalent costs less in company car tax.
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This is still the case but it's nowhere near what it used to be.

A few years back, most petrols were belching out a lot more CO2 than the "equivalent" diesel. The resulting, much lower tax bill meant that the diesel would virtually always end up costing you much less, regardless of the usage of the vehicle, especially for higher-rate tax payers. The fact that diesel used to cost a fair bit less than petrol didn't hurt either! :)

The gap has now closed significantly. When I got my current car nearly four years ago, the equivalent petrol had significantly higher CO2 and would have made a good four or five percentage points difference on the BIK tax. The same car now only saves a couple of percent over the petrol.

On the economy side, I think the gap has also closed here as petrols seem to have made more gains in this area of late than have the diesels.

Basically, whilst a diesel is still cheaper to run, and still slightly more so as a company car, whether the savings are worthwhile is largely down to the individual and the car's usage. As an example, the 2.0T engine looks like a reasonable petrol alternative to my current diesel, yet 90% of my driving is short urban trips and I have a heavy right foot. By all accounts, the economy of the 2.0T under such conditions is diabolical.
 
paradigm said:
I assume he means Company Car Tax (BIC?).

Typically, the diesel equivalent costs less in company car tax.
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Would be interesting to look at those 325 figures quoted above as diesels automatically add 3% to the BIK (Benefit in Kind).

EDIT in fact both BMW 325s, derv and petrol are 23% BIK.
 
What's interesting is that they explained the 3% surcharge for diesels as being due to the high particulate emissions, yet whilst most new diesels now have particulate filters, there's no sign of this surcharge being reduced or removed for vehicles so equipped.

Frankly I doubt the surchage was ever intended to cover particulates but rather because, at the time it was introduced, diesel CO2 emissions were so low compared to petrols that everyone would have switched to a diesel and they'd have lost a shedload of cash :)
 
Vertigo1 said:
Frankly I doubt the surchage was ever intended to cover particulates but rather because, at the time it was introduced, diesel CO2 emissions were so low compared to petrols that everyone would have switched to a diesel and they'd have lost a shedload of cash :)
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Not sure they would have lost a 'shedload of cash' when the pre 2007 rate was flat at £500.
 
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