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.

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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.



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!

[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.

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

When did this happen?

I'd like to know too.

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...