Some calculations

[mikinoz]

I was answering some people on the topic of cost vs gains in having a TDI car. Have a look at the calculations. :D

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For arguments sake I am going to explore some aspects of this discussion in detail using some 'facts' that have been sourced from the internet. My sources are VW website, RACT data on fuel prices and to be fair I have used the RRP for the cars and also the fuel consumption as stated on the cars by the manufacturer (as these are independently tested and based on the same simulations - rather than the real world.

The cars are 2.0 FSI (petrol) Sportline Golf 6sp Manual and 2.0 TDI Sportline Golf 6sp Manual.

http://mjthomsen.gallery.netspace.net.au/albums/spotted/Picture_2.jpg

Cars RRP

The RRP for the FSI = $32,990.
The RRP for the TDI = $35,490.

In this equation there is a premium of $2,500 for the diesel model.

Fuel Consumption

Based on the independent data the fuel consumption is as follows;

2.0 FSI: 8.0 litres per 100 kilometers
2.0 TDI: 5.7 litres per 100 kilometers

In this equation, the petrol car will be using 2.3 litres more per 100 kilometer cycle than the diesel model.

Fuel Price

Based on RACT data for ULP and Diesel in Hobart the following;

ULP: 126.9 cents per litre
PULP: 129.9 cents per litre
Diesel: 132.4 cents per litre

In this equation, the price of diesel is 5.5 cents per litre more than petrol.

So to claim back the $2,500 price difference between the 2 cars the following equation is used;

FSI cost (ULP) per 100 kilometers: 8 x 126.9 = 1015.2 cents
FSI cost (PULP) per 100 kilometer: 8 x 129.9 = 1039.2 cents
TDI cost per 100 kilometers: 5.7 x 132.4 = 754.7 cents

The saving from driving under diesel fuel against ULP in this equation is 260.5 cents.

The distance required to claim the price difference of the diesel engine is as follows;

$2,500 = 250000 cents
25000 cents / 260.5 cents savings per 100km = 959.7 cycles = 95970 kilometers.

For arguments sake if the car covers 15,000 kilometers per year, then it will take 6 years and 146 days to recover the cost.

Now there is another aspect that is not financial, and that is to do with environmental impact through CO2. If only CO2 is calculated, the saving by driving diesel for the 95970 kilometers is as follows;

FSI CO2g/KM per 100 kilometers: 192
TDI CO2g/KM per 100 kilometers: 154

The additional CO2g/KM for the petrol car is 38g per 100 kilometers.

38g x 959.7 100 kilometer cycles = 36468.6g/CO2 = 364.7Kg/CO2

All of that being the case, the diesel car is 0.5 seconds slower to 100Km/h: FSI: 8.8 vs. TDI: 9.3. They should handle identically as they have the same suspension set up. The maximum power and torque will come in earlier with the diesel.

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Let the speculation begin! :D

[REDMKVGTI]

What about servicing costs?

[smithy010]

No Surprises there...

The main reasons i am drawn to diesel engines, are:

A lot of these reasons only apply to old type diesels as well..

- You can run on biodiesel.
- The engines last for longer.
-They are simpler and more reliable.
- They sound great.

The fuel economy is a bonus.

[The_Hawk]

Now run the same sort of comparison with an electric car and see where you end up...


The price difference in the case of the diesel vs petrol is bugger all really. And performance is also on par for the average user. The savings to running Diesel are also small in this case (as you have shown).


It's one of those things, you pay a premium to be nice to the environment and to help you sleep better at night.

[brackie]

You'd need to chuck resale value into the mix. Generally this is higher on a diesel than on a petrol.

Servicing the diesel may also be slightly more expensive as (if you love your engine) you'd need to change your fuel filter more regularly than recommended, and I'd like to know the cost comparison between the cambelt service for the two engines.

Fuel costs vary greatly depending on global supply and demand. At present heavy supply of diesel fuel to Asia is pushing the price up. This was not the case 30 years ago when diesel was up to 10c cheaper per litre than petrol. Who knows how this will change in the near future :???:

Driving technique can affect fuel consumption enormously. According to the computer I got 4.9L/100km on a trip to Launceston (300km) last Friday. This included 110kph on much of the Bass hwy, and also a lot of running around town, whereas 2 weeks ago it was 5.1 on a trip to Hobart when I was a little more "enthusiastic" in my technique :)

I won't go into why I love diesels, 'cos it's a personal thing.

[gldgti]

all that is as may be..... but i love the fact that the diesel has so much cheap horsepower waiting to be gained, without shortening the engine life or making your fuel economy worse.

thats why i love 'em - the fact that you can tune the diesel to have twice stock power and a lot more torque, but still get great economy when your driving normally.

[evorobin]

the fact that you can tune the diesel to have twice stock power and a lot more torque

When did this happen?

[Oneofthegreats]

Alway's thought a diesel was heaps cheaper to run overall than that.
The way you put it doesn't make it that attractive & makes perfect sense Mick. Nice work.

But I'll agree with brackie about the resale. When my brother was selling his TDI, the dealership gave him back what he paided for it without question. There was a shortage of 2.0TDI's at that time.


They sound great.

:rolleyes: I don't know about that. Must love the sound old tractor's on a cold morning.j:


When did this happen?

I'd like to know too.j:

I remember a bloke down my way who played with turboing the old 1.5L Diesel mk1 a couple of time's.

It cost him mega buck's to get it right (went through 3 engine's before everything fell into place) & it still didn't go anywhere near as good as my old beater. Even my stock freaky 1.6L could blast past it. I felt sorry for him spending all that coin & it still didn't make 100hp. In gear performance wasn't that crash hot either.

Saying that though, I can remember an article in "The Golf" magazine about a tuned mk1 diesel that ran low 14's at Santa Pod. Cost him a packet too.

Don't get me wrong, I'm not knocking diesel's. I'd love to fit a tuned 2.0LTDI into a mk1.

[gldgti]

When did this happen?

a tdi will put out 200 whp easily with some quality modification.

you guys who have experience with aussie delivered 1.5 n/a diesels dont understand what a vw diesel is really about - we missed out on all the fun of the 1.6TD - an engine capable of 200whp itself in the extreme, and commonly boosted to well over 100whp from the stock 72hp and 130Nm.

try to think outside the box we call australia, and its diesel-phobia that was wrongfully started by our government before i was born.

[evorobin]

Never really caught on though did it...

[Rod_H]

I love my Diesel too, mum.....
I don't give a stuff what it cost I love the torx... and the tractor sound...
And I only fill up every 3 weeks or so!....

[Edison]

I am ONLY ever getting diesel from now on. It's better on all fronts.

Simple. same reason the bettle was a success, no radiator simplicity for it, no distributor/leads/sparks/coil/contacts ect. Simple. Reliable.

I like it for more power at lower revs, I always have old cars, I always take it easy to prolong their life. First car I had taught me this after 155kms on the f3 to 'see what it'd do' it dumped its fanbelt and loosened a bolt on the alternator? i think, problems emerged, so from then on low revs are the go, and the engines love it. I'll take you broken cam busted head gasket car and drive it another 3,000 k's by this technique any day.

The engines are built better.

waste vege oil. $0.00 cents per litre.

Theres nothing tow starting can't fix.

Lose an alternator in the daytime and drive another 400km's +

[Bazzamon]

I did my comparisions between 2.0l petrol comfortline/auto & the 1.9l diesel/comf/DSG. Both the same price $32290 The 1.9 diesel av quoted 5.7l/100..I get average closer to 4.9/5.0l/100. One does not have to find 98ron. & you have less unshedule maintenance EG cleaning inlet manifold , ign coil failure etc. And no engine oil usage problems. The 1.9l puts me way in front & its power output is still quite respectible. I love my 1.9 diesel Bazz

[BarneyBoy]

You're absolutely right about resale.
I hear it all the time: "but a diesel costs $2500 more..."
But you get back the proportional amount when you sell it.
For example, with a 62% resale value after 3 years (Red Book), you recoup $1550 - so after 3 years, that diesel only actually cost you <$1000 more ($333 per year).
Once you factor that in, the break-even point is very soon.

[Big Al the Butchers' Pal]

You need to do the calculations for Golf 1.6 Petrol vs Diesel

This car runs on stock unleaded. According to my calculations

$2500 extra costs me 13% lost investment income in my share fund per annum = $325 per year.

Extra fuel consumption is 2 litres per 100km.

So, to even start paying off the $2500 cost, I have to save more than $325 per year in fuel.

You forgot to factor lost opportunity cost of the extra cost.

Also the fuel cost is now 15 cents cheaper for a 1.6 petrol vs diesel.

This equates to a 0.8 litre per 100km equivalent fuel saving at current prices.

Half of the saving in consumption is blown in extra fuel cost.

Even if I travel 20,000 km per year, I am still behind in cash terms and the $2500 outlay will never be paid off, no matter how long I keep the car.

Then you have the issues with dual mass flywheels that cost major dollars every few years etc.

And PRAY you never need to do major engine repairs on a diesel engine, as that is mega dollars.

And Pray you never get a shonky (added kero + heating oil) load of diesel or water in the fuel, as that will totally stuff your engine and require a full engine rebuild.

[Tim]

what about the bit where u get depressed cos u drive a 1.6 with no poke? and youre wife leaves u cos youre a cheapskate and u lose your job cos youre always grumpy and then u have to get the dole?

I think the unseen costs of owning a 1.6L golf are far worse than the extra cash u may have to spend on a diesel. :)

[mikinoz]

All good points, however I would prefer to pay more and own a TDI than own another 1.6lt petrol! I still cannot see how you come at using the 1.6 vs 2.0TDI as the cost in purchase is more expensive that the illustration above.

TDI was for me a choice based around wanting a more economical car than a 2.5T Forester and keeping some performance, and not being able to justify the GTI for the use the car was going to receive.

[Big Al the Butchers' Pal]

Sorry, my error in not being more specific.

I compared my car to the exact same car, but with the equivalent diesel engine. As far as I am aware the diesel engine that cost $2500 extra was the 77kW diesel engine. From memory the 0-100 time was 0.1 seconds quicker than the 75kW petrol engine.

As for the comments re the Golf 1.6, as far as I am concerned it is a better car than the Toyota Corolla, albeit with a less powerful engine.

The Golf was cheaper than a Corolla with the same safety features specification (as Toyota charged extra).

But then again, there is also some merit in having a simple 2 valve belt driven OHC engine with a simple Siemens ECU setup and a clutch that does not involve a dual mass flywheel.

I also see merit in the fact that the 1.6 sold in Australia is a destroked version of the 85 KW 2.0 litre engine. I prefer a short stroke engine with long connecting rods as it is free revving and easy to drive in manual form. As far as I am aware the Golf 1.6 is the only oversquare passenger car engine currently sold by any manufacturer. Even the Hyundai Gets 1.6 has an extra 20mm stroke than a Golf 1.6.

[TDI Dude]

Well gentlemen I'll just say one thing on this subject.... YOU BUY A DIESEL AS A CHOICE NOT BECAUSE THE ACCOUNTANT SAID SO!!!! P.S. cant wait for mine to turn up!!!!!! :D

[Logzy]

Im getting a diesel to satisfy my fetish i have at the moment with Turbo Diesels.
I just like the idea of them.

I wouldnt get a 1.6l petrol that needs to have the ring hole revved out of it to produce the power so for low fuel consumption a diesel is for me.

I'm going from a VXII 5.7l Clubsport that averages 14l/100k so the way i see it I'll be saving heaps in fuel and I'll have a engine that will last instead of a 4cyl petrol engine that needs to be revved.

The fuel price for me is about the same as diesel per litre as the clubby needs 98RON
I'll save about $45-$50 a week in fuel, not to mention another $360 a year in insurance and $$ in tyres.

[mikinoz]

As for the comments re the Golf 1.6, as far as I am concerned it is a better car than the Toyota Corolla, albeit with a less powerful engine.


I have to say the 1.6 MKV that I drove was reasonable and a huge advancement over the 1.6 MKIV in standard form! :cool: My company car is a corolla and they are 2 different beasts indeed!

[GermanwithaVdub]

can someone confirm what im about to infer.

i dont have much experience with an mkv fsi, but im guessing that if you're a person who constantly revs close to redline and always hard acceleration, that you're going to use exponentially more fuel than if you drive the same way in the equivalent diesel?

[Big Al the Butchers' Pal]

can someone confirm what im about to infer.

i dont have much experience with an mkv fsi, but im guessing that if you're a person who constantly revs close to redline and always hard acceleration, that you're going to use exponentially more fuel than if you drive the same way in the equivalent diesel?

You are correct. The efficiency of an internal combustion engine is proportional to the compression ratio. A diesel engine has far greater compression (11 to 1 vs 19 to 1), and is thus more efficient. The cost of this efficiency is however higher engine drag torque. This is the case because the internal moving and reciprocating parts are heavier and also because more work needs to be done to achieve the higher compression. The engines are also heavier. The 2.0 TDI engine is 140kg heavier than a 1.6 petrol engine. A TDI engine also needs to use 20% of engine output to drive the turbocharger via the exhaust stroke.

Diesel engines are therefore around 30% more efficient in producing power. This is why diesel engines are used exclusively for power applications such as generators, compressors, ships, pumps and trucks. Diesel engines are however less efficient that petrol engines in NOT producing power, because the drag torque is double that of a petrol engine.

So for aero applications and motor vehicles, where the engine spends the majority of the time at part load, the petrol engine will be more efficient in non full load situations. This is why I get over 900 km from a tank of fuel in my car, because I spend most of the time cruising on the highway at 80 to 100k/h at a 10 to 20% of full load application.

If I were however to go on the autobahn at 180km/h flat pedal, my car would drink like an Irish sailor. The diesel engine would be far more efficient in such a constant full load situation.

If you are a lead foot then the diesel will be a better choice, however driven ultra efficient, the petrol engine will be (in overall terms) more efficient than an equivalent diesel engine. This example was proved in the recent fuel consumption world record where a petrol VW Golf achieved that record.

[Big Al the Butchers' Pal]

Well gentlemen I'll just say one thing on this subject.... YOU BUY A DIESEL AS A CHOICE NOT BECAUSE THE ACCOUNTANT SAID SO!!!! P.S. cant wait for mine to turn up!!!!!! :D

You are correct in your analogy. I buy Benson & Hedges as a choice, not because my doctor said so.

[GermanwithaVdub]

You are correct. The efficiency of an internal combustion engine is proportional to the compression ratio. A diesel engine has far greater compression (11 to 1 vs 19 to 1), and is thus more efficient. The cost of this efficiency is however higher engine drag torque. This is the case because the internal moving and reciprocating parts are heavier and also because more work needs to be done to achieve the higher compression. The engines are also heavier. The 2.0 TDI engine is 140kg heavier than a 1.6 petrol engine. A TDI engine also needs to use 20% of engine output to drive the turbocharger via the exhaust stroke.

Diesel engines are therefore around 30% more efficient in producing power. This is why diesel engines are used exclusively for power applications such as generators, compressors, ships, pumps and trucks. Diesel engines are however less efficient that petrol engines in NOT producing power, because the drag torque is double that of a petrol engine.

So for aero applications and motor vehicles, where the engine spends the majority of the time at part load, the petrol engine will be more efficient in non full load situations. This is why I get over 900 km from a tank of fuel in my car, because I spend most of the time cruising on the highway at 80 to 100k/h at a 10 to 20% of full load application.

If I were however to go on the autobahn at 180km/h flat pedal, my car would drink like an Irish sailor. The diesel engine would be far more efficient in such a constant full load situation.

If you are a lead foot then the diesel will be a better choice, however driven ultra efficient, the petrol engine will be (in overall terms) more efficient than an equivalent diesel engine. This example was proved in the recent fuel consumption world record where a petrol VW Golf achieved that record.

ah thanks for that, very clear now :)

[neil]

You'd need to chuck resale value into the mix. Generally this is higher on a diesel than on a petrol.

Servicing the diesel may also be slightly more expensive as (if you love your engine) you'd need to change your fuel filter more regularly than recommended, and I'd like to know the cost comparison between the cambelt service for the two engines.

Fuel costs vary greatly depending on global supply and demand. At present heavy supply of diesel fuel to Asia is pushing the price up. This was not the case 30 years ago when diesel was up to 10c cheaper per litre than petrol. Who knows how this will change in the near future :???:

Driving technique can affect fuel consumption enormously. According to the computer I got 4.9L/100km on a trip to Launceston (300km) last Friday. This included 110kph on much of the Bass hwy, and also a lot of running around town, whereas 2 weeks ago it was 5.1 on a trip to Hobart when I was a little more "enthusiastic" in my technique :)

I won't go into why I love diesels, 'cos it's a personal thing.

Hey brackie.
Good to see you still around.
Have missed your posts re: fuel consumptions.

Did a trip from Sydney to Young via Boorowa approx 380km @ 4.7 L/100
Return trip, took it easier via Wombat 350 km @ 4.1 L/100:D
Was sitting on 4.0 until I hit the city.
Anyway how do these manufactures get the figures they state on the
brochure. I cant get anywhere near there estimate of 6.1 even in the city.
Take care Neil.

[evorobin]

You need to do the calculations for Golf 1.6 Petrol vs Diesel

This car runs on stock unleaded. According to my calculations

$2500 extra costs me 13% lost investment income in my share fund per annum = $325 per year.

Extra fuel consumption is 2 litres per 100km.

So, to even start paying off the $2500 cost, I have to save more than $325 per year in fuel.

You forgot to factor lost opportunity cost of the extra cost.

Also the fuel cost is now 15 cents cheaper for a 1.6 petrol vs diesel.

This equates to a 0.8 litre per 100km equivalent fuel saving at current prices.

Half of the saving in consumption is blown in extra fuel cost.

Even if I travel 20,000 km per year, I am still behind in cash terms and the $2500 outlay will never be paid off, no matter how long I keep the car.

Then you have the issues with dual mass flywheels that cost major dollars every few years etc.

And PRAY you never need to do major engine repairs on a diesel engine, as that is mega dollars.

And Pray you never get a shonky (added kero + heating oil) load of diesel or water in the fuel, as that will totally stuff your engine and require a full engine rebuild.

ABRZ from vortex australia has entered the building LOL

[Spoddy]

Anyway how do these manufactures get the figures they state on the
brochure. I cant get anywhere near there estimate of 6.1 even in the city.
Take care Neil.

We seem to have found the method.... short trips to the station where the car doesn't warm up :( Seems such a waste driving a car that way but then its my wife's car and thats the only way to get to work. We are averaging 6.8 whilst the silly MFD says 5.9 to 6.1.

[neil]

We seem to have found the method.... short trips to the station where the car doesn't warm up :( Seems such a waste driving a car that way but then its my wife's car and thats the only way to get to work. We are averaging 6.8 whilst the silly MFD says 5.9 to 6.1.

Interesting spoddy.

I'm quoting the MFD, I'll do a few manual calculations and see what
I come up with.
neil.

[GermanwithaVdub]

Hey brackie.
Good to see you still around.
Have missed your posts re: fuel consumptions.

Did a trip from Sydney to Young via Boorowa approx 380km @ 4.7 L/100
Return trip, took it easier via Wombat 350 km @ 4.1 L/100:D
Was sitting on 4.0 until I hit the city.
Anyway how do these manufactures get the figures they state on the
brochure. I cant get anywhere near there estimate of 6.1 even in the city.
Take care Neil.

you must drive VERY conservatively. i was lucky to get 6.1 or below on my 2.0tdi comfortline when i had it. mostly up around 7 or 7.5. and you cant count the cruising on a highway, i can make my car sit at 3 point something on a straight flat stretch, it has to be a mix of city/highway to have relevance.

[neil]

you must drive VERY conservatively. i was lucky to get 6.1 or below on my 2.0tdi comfortline when i had it. mostly up around 7 or 7.5. and you cant count the cruising on a highway, i can make my car sit at 3 point something on a straight flat stretch, it has to be a mix of city/highway to have relevance.

Yeah, most of my driving is long distance.
But city driving I have learnt to conserve fuel by getting off the
accelerator as soon as I see a red light and try and pick the change to green
while still in secound. Still get great economy in city, around 5.1

[TDI Dude]

You are correct in your analogy. I buy Benson & Hedges as a choice, not because my doctor said so.

I'll drink to that also!!!!!!!!! Cheers :D

[Big Al the Butchers' Pal]

ABRZ from vortex australia has entered the building LOL

I was banned from the VW Vortex! (I think because I did not meet the membership criteria)

I found this forum because I did some Googling as my warranty is due to expire shortly.

I think that this forum is more useful and informative, as the contributors seem to actually use the forum for its intended purpose.

I do however still visit VW Vortex if I need advice on which socks to wear or which mobile telephone to buy.

[gldgti]

can we get this discussion back onto fuel economy somehow guys? cheers :-)