Help Needed - I'm Crap At Maths

[Grumpy Cabbie]

I've had the Prius working as a cab one year on November 3rd, 2010 and I'm wanting to do a little report on how good it is on fuel economy and emissions to show the local taxi inspector.

I'm crap at maths so I'd be grateful for someone to check my figures are correct and also convert them into percentages etc. Now my average consumption so far (as you can see from my fuelly) is coming in at 49.2 mpg. Now over 34,100 miles (will probably 35k by 3/11/10) that works out at 711 gallons? Which at an average cost of say £1.15 a litre works out at 3228 litres or £3,710 a year. This is pretty much close to what I got in reality.

Now how do I show how many metric tonnes of CO2 I have saved compared to a car doing 40 mpg, 35 mpg, 30 mpg & 25 mpg in costings AND percentage savings? Also, I want to show the savings of NOx compared to say a modern diesel engined taxi (Mondeo diesel?) on the above mpg's (40, 35 etc) and then I'd like to show how this equates if say 100 of the 500 taxis in our town suddenly became Prius's overnight etc. There was a recent article in the local paper saying that the town failed on NOx pollution in certain parts and I'm sure if more taxis were Prii, then this might not be so bad. Of course the 10 year old smoggy buses in town don't help any! :censor:

I told you I'm no good at maths - if I was I know I wouldn't be driving a cab round for a living! lol. Can anyone more arithmetically minded help or do the above sums for me so I can have my presentation ready for the cabs annual birthday in November?

Cheers guys n guyettes.

[Carltona123]

Easy peasy. Excel Spreadsheet. Job done.

[Grumpy Cabbie]

So says the accountant.

I'm just a poor humble cabbie and don't posses such things as excel.

[wooski]

A lot of assumptions here.

Your calculations are correct. Your 35K miles = 56329Km. So that's 5.01 tonnes CO2 and 337.9 g NOX

Assuming a 2 litre Mondeo diesel auto - will do around 29mpg urban, cost £1.20 a litre, puts out 187g CO2 and 216mg NOX (Prius is 6mg NOX)

Thus you would need 1206 gallons, 5479 litres costing £6,575 which is £2,861 more or 77% more

CO2 would be 10.5 tonnes, 5.5 more or 110% more

NOX would have been 12,167g, or 11,829g more or 3500% more!

That Mondeo is Euro 4. Ford must have a Euro 5 version coming (which will have lower NOX).

(I did this in Excel too!)

[Carltona123]

So says the accountant.

I'm just a poor humble cabbie and don't posses such things as excel.

Oh you don't need Excel yourself, just a grandson/grandaughter who's got it. Or a neighbour's kid.

I'm no expert either, but I'm thinking you could just copy all your text about nitrous oxide etc then paste it into an Excel cell then hit the autosum button and presto. I think.

[Grumpy Cabbie]

Wow I knew diesels were bad for NOx but I thought i had got my sums wrong. Is it really 3500% more than my actual figures? I just can't believe a diesel taxi will produce that much more.

Also, I really want to get the figures correct otherwise I'd look a right prune. If 3500% more is correct then increasing the number of hybrids will make a significant difference to the towns pollution. I might also write a letter to the local rag but again I want to make sure my sums are correct.

Any help from the less arithmetically challenged would be appreciated.

[cootuk]

I thought the CO2 (g/km) figures quoted for cars were based on the extra urban mpg so real world emissions can be quite different.

http://www.eta.co.uk/2010/02/22/calculating-car%E2%80%99s-co2-emissions-its-mpg

A petrol car has g/km co2= 6760/mpg

A diesel has g/km co2= 7440/mpg

Your true co2 level is more like 134g/km than the quoted 80g/km as this assumes 76mpg.

Doesn't look so good when calculated not using the car manufacturers set figures, but then it all depends

on real world mpg.

As for NOx, the stated Prius is <0.010g/km whereas a typical Mondeo diesel is 0.235g/km so a x24 difference.

[Grumpy Cabbie]

The mpg's quoted by wooski are about right - 49 mpg for me and 29 mpg for a mondeo diesel. Remember these are about right for town use

[wooski]

I got these from http://www.vcacarfueldata.org.uk/

As we are talking a minicab I have gone for the automatic gearbox model:

Prius G3 T3 is 89g CO2 / km and 6mg NOX / km

2010 Ford Mondeo 2.0 TDCI Auto (140ps) is 187g CO2/km and 0.216g NOX/km = 216mg NOX / km (i.e. 35 times more)

It will be interesting what the newer diesels with urea injections fair. The new Mercedes 350 CDI blutec which has this technology has NOX levels down from 0.197g to 0.065g NOX and is Euro6 rated. However 65mg is still 10 times more than the Prius. As a comparison the current S500 with a 5 litre V8 petrol has NOX emissions of 0.031g. And I read somewhere that the Adblue urea costs well over £1,000 every 15K miles to top up.