Petrol vs Diesel: A 10 year urban running cost comparison

[Whitey]

Hey all,

This is a redo of the plot in post #92 without the range, just a simple savings vs economy. This way you can look up whatever diesel economy you are getting and see what the average savings is per year;



This data is with respect to an average economy of 15.2l/100km for the petrol.

The savings includes fuel + service schedule + rego.

One other factor to consider for diesels is if you get better economy figures by throttling the egr system with a reducing plate. This graph should be considered only as relative for an unmodified diesel.

If you get better economy by essentially bypassing/limiting the egr system, then you are running a vehicle which is polluting significantly more than when it came out of the factory, and that type of diesel should be considered as another comparison outside this model.

Best

Mark

[photoprado]

Hey,

Just put human readable numbers in and save everyone except maths/science geeks confusion.

1.25e+5 is 7 characters
125000 is 6 characters

So it saves a lot of bandwidth too

[Whitey]

Hey,

For those who don't like the scientific notation, here it is in simpler engineering notation;



Best

Mark

[brogers]

Hey,

Ok, if you want to be pedantic, the "e" is shorthand scientific notation, and the "e" refers to the exponent.

1.25e+5 = 1.25x10^5 = 125000.

Nothing confusing about it. Multiple graphing software programs that output this notation.

...and yes, in this case you are very wrong.

Best

Mark

yep, indeed 1.25e+5 is 125,000
but 1.2e+5 (which I thought he was referring to) is 120,000
...either way, it is indeed shorthand scientific notation, however e in this instance is not referring to the mathematical constant (Euler's number) ....its a shorthand way of displaying large numbers. But no more, its of topic anyway.

[Whitey]

Actually if you want to be pedantic, e is known as Eulers number and equals approx 2.718281828,
Its one of those mathematical constants that made sense to some esoteric mathematician and confuses the heck out of the rest of us....

so 1.2e+5 actually equals 178.096
for further information see the wikipaedia article.

ps not looking for an argument nor a prolonged discussion if I am wrong then so be it.

Hey,

Ok, if you want to be pedantic, the "e" is shorthand scientific notation, and the "e" refers to the exponent.

1.25e+5 = 1.25x10^5 = 125000.

Nothing confusing about it. Multiple graphing software programs that output this notation.

...and yes, in this case you are very wrong.

Best

Mark

[Corigator]

Just a friendly comment...
I believe that 1.2e+5 is actually scientific notation for 1.2 times 10 to the power of 5 , so that makes it 1.2 times 100,000 which equals 120,000 (and not 125,000)

Actually if you want to be pedantic, e is known as Eulers number and equals approx 2.718281828,
Its one of those mathematical constants that made sense to some esoteric mathematician and confuses the heck out of the rest of us....

so 1.2e+5 actually equals 178.096
for further information see the wikipaedia article.

ps not looking for an argument nor a prolonged discussion if I am wrong then so be it.

[Whitey]

Hey,

I just re-did the model for 98 octane. I've assumed a flat 17c/litre difference between 91 and 98, and a maximum 2l/100km gain in economy. You would save roughly $40/year compared to running ULP.

Keep in mind that is a rough figure, as I don't have historical figures for 98, and the 17c/litre is the difference I saw tonight at the local BP, it will of course vary a lot over the last 10 years.

You will of course use less fuel by running 98, and it will be better for your engine.

Best

Mark

[Whitey]

Hey,

Just checked here;

http://www3.toyota.com.au/prado/spec...xl-petrol-auto

So they are saying 95 is the minimum fuel now, and engine power is 207kW.

Toyotas "urban" figures are 15.5l/100km, very close to the 15.2l/100km used in the model here. Take Toyotas figures with a grain of salt of course!

Kerb weight of the new model is 2220kg, and they claim 9.4l/100km for highway driving. My 120 weighs in at 2.3t with all my ARB gear and decked out rear cargo area, and I get around 11l/100km for highway driving using 98. Different aerodynamics I know, but hard to believe you can get down to 9.4l/100km using 95. A loaded up 120 diesel is down to 10l/100km with highway driving!

Best

Mark

[Whitey]

Did the calculation include premium unleaded? Thats the minimum requirement for the petrol now? Suspect thats why they quote 11.5l/100km. Usually get 1 to 2 litres better with 95 - 98 RON

Hey cuda,

The model is only for ULP and for 120 series Prados. ULP is the only historical data available. I could make some assumptions about how much more it is for 95 or 98 and scale the average, but it wouldn't be accurate.

I didn't know that Toyota are now saying the petrol has to be run on premium!? As far as I'm aware, it's still the same 1GR-FE tweaked out to 200kW?

Is 11.5l/100km the urban figure Toyota are claiming for the petrol?

Best

Mark

[cuda]

Hey,

There aren't any "stuff ups" in the model. That is why the model uses the national average for fuel prices stretching back 10 years.

The relative price difference between diesel and petrol may change depending on where you are, but diesel is typically always more expensive than petrol, and it has been that way for over 10 years.

If you redid the model using prices from say Innamincka, you would get similar outcomes.

Comparing a petrol driver in Melbourne to a diesel driver in the bush is hardly fair, and the petrol will obviously win that cost race hands down.

If you want a fair comparison and interpretation, you have to compare the diesel and the petrol under similar driving circumstances.

Best

Mark

Did the calculation include premium unleaded? Thats the minimum requirement for the petrol now? Suspect thats why they quote 11.5l/100km. Usually get 1 to 2 litres better with 95 - 98 RON

[Whitey]

Another factor that stuffs all of those theories up is the price of fuel - both the difference between ULP and diesel and the price variation from city to city, region to region and state to state. Somebody in Melbourne enjoying cheap ULP could be miles ahead of a country fella in a diesel.

Hey,

There aren't any "stuff ups" in the model. That is why the model uses the national average for fuel prices stretching back 10 years.

The relative price difference between diesel and petrol may change depending on where you are, but diesel is typically always more expensive than petrol, and it has been that way for over 10 years.

If you redid the model using prices from say Innamincka, you would get similar outcomes.

Comparing a petrol driver in Melbourne to a diesel driver in the bush is hardly fair, and the petrol will obviously win that cost race hands down.

If you want a fair comparison and interpretation, you have to compare the diesel and the petrol under similar driving circumstances.

Best

Mark

[Bushbasher]

Another factor that stuffs all of those theories up is the price of fuel - both the difference between ULP and diesel and the price variation from city to city, region to region and state to state. Somebody in Melbourne enjoying cheap ULP could be miles ahead of a country fella in a diesel.

[Whitey]

Just a friendly comment...
I believe that 1.2e+5 is actually scientific notation for 1.2 times 10 to the power of 5 , so that makes it 1.2 times 100,000 which equals 120,000 (and not 125,000)

Hey,

You are correct of course, sorry, slip of the mind and keyboard!

Best

Mark

[photoprado]

Perhaps it would be better to just put in the real numbers instead of playing scientist mumbo jumbo.

[brogers]

1.2e+5 = 125000, it's the scientific notation in SigmaPlot.

Just a friendly comment...
I believe that 1.2e+5 is actually scientific notation for 1.2 times 10 to the power of 5 , so that makes it 1.2 times 100,000 which equals 120,000 (and not 125,000)