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Petrol versus The Black Art of Oil Burning

I've just landed myself a new job, however it will mean my daily commute quadruples from 20 to 80 miles, meaning my annual mileage will be around 20k a year, if not slightly more once I factor in weekend jaunts. I'm currently 2 years into a PCP on my MiTo Cloverleaf and managing just under 40mpg during dull commuter runs. With my new increased mileage, do I have to bite the bullet and think the unthinkable - buying a diesel?

I had a Guilietta diesel as a courtesy car, and it was very nice, it just lacks the noise of it's petrol counterpart. For those of you on here who own a diesel, why? What is your annual mileage, and are you actually saving money or is it a preference? I know some diesels quote mpgs as high as 70, but this is offset against more regular service intervals.

(As a yardstick, I'm test driving the A class diesel on Sunday - strictly for research purposes, please don't ban me!)
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Get a go in a 170hp jtdm2 and you will never return to the benzine side of the room! Imagine never changing gear to go up a hill at the same speed, if not accellerating up it!!
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Although I'm currently driving a petrol 156, I love diesels for the low down grunt they give. A lot of the modern diesels (especially the 2.4jtdm 159 I had) do actually sound half decent too.

However, I think if you do the sums, taking into account the cost of getting out of your current PCP, and the extra cost of diesel over petrol - and bearing in mind that diesels can still be relatively thirsty if driven hard (I only ever got 31mpg out of a very hard driven Jag S-Type with the excellent 2.7 twin turbo diesel), you won't be making the savings you're hoping for. Also, on steady speed motorway runs, petrol engines can be surprisingly economical.

Taking all that into account, my guess is that you'll be better off sticking with the MiTo until the end of your Contract and then maybe consider a diesel after that.

Very best of luck with the new job!
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My 147 is the first oil burner car I have ever owned, I have covered over 58000 miles in it and have now got to the point of preferring it to petrol, power where its most usefull, lazy in town, bags of grunt, fantastic tank range, adapt your style of driving and enjoy the difference !
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My gut feeling is that it's never economical to change a car before three years, so I'd second the "see out the Mito, then change" advice.

If you do go diesel, the TCT on the 2.0 is a great combination, and slightly more economical than the manual one.
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Convert your Mito to LPG!


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I either commute in a 156 V6 or a 159 2.4. Work pays the bills, so consumption doesn't come into it.

Yes, the petrol sounds better, but it is also more wearing. 4000 rpm on the motorway gets on your nerves after a while. You're not having fun, you're going to work. Though finding some quiet bits on the back roads is a joy.

The diesel - well on the motorway, you're just moving. The engine is spinning at a relaxed 2000 rpm, there is a huge seam of torque under your right foot, and it is easy. It is not as aurally fun, but when driven correctly, the diesel is an awesome overtaking tool.

For 80 miles a day, I'd take diesel, but put it in a decent sized saloon. I've been less happy with small diesels.
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I do 100 mile a day for work commute - althought now car shared halfs the miles it still saves me money in fuel. The JTD 170 makes sure i have performance and it makes me smile when the goverment doesnt get loads of road tax off me.

However its not all quite as simple as our other car is a fiesta ST 2.0 petrol, fiesta gets about 36mpg, alfa about 47mpg but that equates to about 3-4 extra per 100 miles
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Depends on the cost to end your PCP early, and the penalty if you go over the mileage limit with your PCP if you continue to use that. If those costs are high, could even be worth buying a sub-1000 diesel or LPG smoker to run just as a commuting tool for a year.

If you are getting 40mpg from the Mito, there aren't many real-world diesels that will get much over 50mpg unless you are really anal about fuel saving, so you'll not make huge savings with a switch to diesel.
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I don't get the whole 'diesels have more low down grunt than petrols' - diesels don't, a truer statement would be 'turbocharged engines have more low down than non-turbocharged engines'
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I don't get the whole 'diesels have more low down grunt than petrols' - diesels don't, a truer statement would be 'turbocharged engines have more low down than non-turbocharged engines'
Very valid point; but diesels do generally produce proportionately more torque than an equivalent petrol turbo. It's an interesting observation though because I always considered that my Seat Ibiza (1.8 Turbo Petrol) drove like a diesel because it pulled so strongly from very low revs!
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Very valid point; but diesels do generally produce proportionately more torque than an equivalent petrol turbo. It's an interesting observation though because I always considered that my Seat Ibiza (1.8 Turbo Petrol) drove like a diesel because it pulled so strongly from very low revs!
But once you factor in the difference of gear ratios, the diesel doesn't have more torque

Eg. 159 2.4jtdm & 1750tbi :

2.4 has 295lb at 2000rpm, 1750 has 236lb at 2000rpm

If you floor both in say 6th gear at 75mph :

Power from 2.4 is 295/5250x2000 = 112bhp

Power from 1750 is 236/5250x2600 = 117bhp
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I quite agree that gearing is a big factor; but surely it's because of the extra low down torque in a diesel that it's able to pull much higher gearing than the petrol? I'm afraid I'm not clever enough to understand the calculations you've used, but surely the Torque figures you quote prove that the diesel has 25% more pulling power at 2000 revs?

Please don't take this that I'm trying to rubbish your idea Phil - I'm not; I'm just interested in your opinion because it's a different angle on this long-standing diesel v petrol debate that I'd not really thought about before.
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Quote:
Originally Posted by rgwm View Post
Depends on the cost to end your PCP early and the penalty if you go over the mileage limit with your PCP if you continue to use that. If those costs are high, could even be worth buying a sub-1000 diesel or LPG smoker to run just as a commuting tool for a year.
What he said.
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I switched from a petrol Brera to the 170 diesel Giulietta. The 2.4 isn't a modern diesel. (sorry guys, it's been around for years)

Let's compare the 2.0 170 to the 2.4 200:
Alfa Romeo Giulietta III 2.0 JTDm vs Alfa Romeo 159 2.4 JTDm [34461369]

How about comparing the 2.0 170 to the fabled V6...
Alfa Romeo Giulietta III 2.0 JTDm vs Alfa Romeo 156 V6 [344610]

...it's clear that the V6 will blow the diesel away in a standing start, but in real world driving - e.g. when overtaking from 40-60 or 50-75, the 170 diesel outperforms the V6

So, performance isn't an issue, unless you're drag racing.

Now let's do a quick economy comparison...

Car///156 V6/159 1750/159 2.4/Mito QV/G 170D
MPG///23.9///34.9//////41.5/////47.1/////60.1
Noise//73.5///73////////75///////73.5/////74.5
Tax///280///260//////220////125/////105
Fuel///3150/2157/////1906///1598///1316

(these figures are from the government website, the Fuel value is cost of fuel for 12,000 miles)

In other words, a Diesel Giulietta will cost you less than half as much as a 156V6 in fuel & tax each year, and will be able to sail past it on a motorway.

But based on the OP's figures of 20,000 a year, the Giulietta will save him roughly 500 in fuel compared to his Mito QV, according to the government.

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I have had 7 156s two 2.0 Twin sparks/ 1 jts /2 10v jtds/ 1 16v / and my 20v.
All the diesels were better.Not had a v6 yet I beleave that will be best.
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I quite agree that gearing is a big factor; but surely it's because of the extra low down torque in a diesel that it's able to pull much higher gearing than the petrol? I'm afraid I'm not clever enough to understand the calculations you've used, but surely the Torque figures you quote prove that the diesel has 25% more pulling power at 2000 revs?

Please don't take this that I'm trying to rubbish your idea Phil - I'm not; I'm just interested in your opinion because it's a different angle on this long-standing diesel v petrol debate that I'd not really thought about before.
what you've said is not untrue

the essence of what I was saying is that for an identical driving speed, in an identical gear at full throttle the petrol turbo car in this example would give you more acceleration than the diesel
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Quote:
Originally Posted by fiisch View Post
I've just landed myself a new job, however it will mean my daily commute quadruples from 20 to 80 miles, meaning my annual mileage will be around 20k a year, if not slightly more once I factor in weekend jaunts. I'm currently 2 years into a PCP on my MiTo Cloverleaf and managing just under 40mpg during dull commuter runs. With my new increased mileage, do I have to bite the bullet and think the unthinkable - buying a diesel?

I had a Guilietta diesel as a courtesy car, and it was very nice, it just lacks the noise of it's petrol counterpart. For those of you on here who own a diesel, why? What is your annual mileage, and are you actually saving money or is it a preference? I know some diesels quote mpgs as high as 70, but this is offset against more regular service intervals.
I bought the diesel for economy and cheaper VED. I have never driven a V6 Alfa and only my GT so cannot compare it with like for like.
My Spider is the Alfa I enjoy the most by a long way. The GT was my head ruling over my heart just a little more

Annual is currently about 18k across four cars. Not sure what the GT does off the top of my head.
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what you've said is not untrue

the essence of what I was saying is that for an identical driving speed, in an identical gear at full throttle the petrol turbo car in this example would give you more acceleration than the diesel
Except you quoted the 1750TBi torque at 2000, then changed the figure to 2600 for your calculation (yes, I know that's due to gear ratios and the 1750 is known for having a flat curve), but let's look at a different calculation - same revs...

2.4 @ 2000rpm = 112bhp
1750 @ 2000rpm = 90bhp

So, it's quite clear that at the lower revs the diesel has more power.

...then go to a modern diesel and save yourself 1000 every 12,000 miles, and my little 170bhp diesel hits 258lbs from 1750rpm, so at 2000rpm I've got 98bhp
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Except you quoted the 1750TBi torque at 2000, then changed the figure to 2600 for your calculation (yes, I know that's due to gear ratios and the 1750 is known for having a flat curve), but let's look at a different calculation - same revs...

2.4 @ 2000rpm = 112bhp
1750 @ 2000rpm = 90bhp

So, it's quite clear that at the lower revs the diesel has more power.

...then go to a modern diesel and save yourself 1000 every 12,000 miles, and my little 170bhp diesel hits 258lbs from 1750rpm, so at 2000rpm I've got 98bhp
I think that you're missing the point that I'm making regarding the actual performance of the cars on the road
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I'd made that point earlier - the Giulietta in real life circumstances has better performance than the likes of the V6.
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I'd made that point earlier - the Giulietta in real life circumstances has better performance than the likes of the V6.
please refer to my 1st post of the thread..
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Lol - has this now turning into a debate about which is best out of Diesel, Turbo Petrol or V6.......

I must admit that in my opinion, normally aspirated V6's have had their day now (yes; I know you can't beat the sound of a V6), because modern Turbo Petrol's are so good. I also think that modern diesels are no longer the sensible option if you're looking for reliability in an engine - too many ill-conceived add-on's now, to try and make them more green (DPF, EGR), have made them a nightmare for the average motorist.

I guess that means I fall into the Turbo Petrol is best camp. As I said above, the VW Group 1.8T is an absolute gem of an engine. Last week I did 1400 miles in France in an Audi A3 with 4 on-board, powered by the 1.2 TFSI engine. It only really lacked power when overtaking from 80+ MPH - the rest of the time the DSG was changing up at less than 3k revs.
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Quote:
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please refer to my 1st post of the thread..
OK:

Quote:
Originally Posted by phil-gtv6 View Post
I don't get the whole 'diesels have more low down grunt than petrols' - diesels don't, a truer statement would be 'turbocharged engines have more low down than non-turbocharged engines'
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Originally Posted by phil-gtv6 View Post
But once you factor in the difference of gear ratios, the diesel doesn't have more torque

Eg. 159 2.4jtdm & 1750tbi :

2.4 has 295lb at 2000rpm, 1750 has 236lb at 2000rpm

If you floor both in say 6th gear at 75mph :

Power from 2.4 is 295/5250x2000 = 112bhp

Power from 1750 is 236/5250x2600 = 117bhp
Quote:
Originally Posted by WTFH View Post
Except you quoted the 1750TBi torque at 2000, then changed the figure to 2600 for your calculation (yes, I know that's due to gear ratios and the 1750 is known for having a flat curve), but let's look at a different calculation - same revs...

2.4 @ 2000rpm = 112bhp
1750 @ 2000rpm = 90bhp

So, it's quite clear that at the lower revs the diesel has more power.

...then go to a modern diesel and save yourself 1000 every 12,000 miles, and my little 170bhp diesel hits 258lbs from 1750rpm, so at 2000rpm I've got 98bhp
So, your first post was that diesels do not have more "low down grunt" than petrols. Except you've proved it wrong yourself, unless you change the rules and say that 2600rpm = 2000rpm.

Low down grunt is not low mph, it's low rpm.
So, does my car, producing 258lbft of torque at 1750rpm produce more torque than your car at 1750rpm?
Yes
Is your car a turbo petrol?
Yes
Is my car a turbo diesel?
Yes.

Want to move the goal posts?
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Who the hell would want to have 1.750 rpm in his Alfa?! There is a special stick left (right in my case) to your seat and, surprise, surprise, it's used for changing gears!
I have a 2.0 TS 1989 Alfa 75 and it's so much more fun driving it than driving the MA, although the TS is 146BHP and MA is 170BHP... I drove Giulietta diesel once or twice and the vibrations during standstill were enough of a put off.

For long motroway commuting diesel is the way to go (especially concerning running costs), but I guess I'd still rather get a 156 (or a 164 - they're insanely cheap right now) V6 LPG in your case - won't be cheaper than selling the MiTo and buying a new car?
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