diesel v petrol

aidanki

going to be buying a car soon so was doing a few sums today

The equation for diesel v petrol for me is

Cost of Diesel for X miles+€2000=Cost of Petrol for X Miles
Lets say a diesel car does 50 miles to gallon and Petrol 40miles to gallon
€2000 comes from additional purchase cost of a diesel car over petrol
Cost of Diesel €8 per gallon, cost of Petrol €8.27 per gallon

When you solve above equation you get 42.8k miles to break even

I assumed that tax and insurance are equal for a petrol and diesel which is fair enough lots of 1.4 and 1.6diesels about these days

so to my mind diesel is the right option at 15k miles per year 3year payback time for forking out the extra for a diesel

have I forgotten something?

colm_mcm

Where'd you get the €2000 figure from?

aidanki

colm_mcm wrote: »

Where'd you get the €2000 figure from?

my guess at how much a diesel is over a petrol when buying secondhand

colm_mcm

It's not usually that simple unless you're thinking of a particular model in a particular year

thebiglad

Resale values?

Service costs?

Doesn't MPG really depend on type of driving - i.e. long distance/motorway are preferable to a Diesel.

randy hickey

aidanki wrote: »

my guess at how much a diesel is over a petrol when buying secondhand

I have been on the hunt for a decent 07 Avensis for a while now, and I just ain't seeing a notable price differential between the petrol and diesel models, let alone two grand.

FrontDoor

randy hickey wrote: »

I have been on the hunt for a decent 07 Avensis for a while now, and I just ain't seeing a notable price differential between the petrol and diesel models, let alone two grand.

Of course the other side of this is that a standard diesel Avensis is far preferable in performance terms to a standard petrol 1.6.

A truer comparison would be a 1.8 or 2.0 petrol surely.

166man

You also need to factor in that with the current trend in Ireland for diesel, whatever you buy if it is a diesel will most likely be worth more than the petrol equivalent when you go to sell it on. It's not just the initial saving in cost price and fuel economy difference of the petrol.

Doubt you'll average 40mpg from too many petrols tbh on driving that a diesel would average 50mpg.

If you divulge your estimated annual mileage and the sort of car you are considering it would help.

aidanki

RoverJames wrote: »

Doubt you'll average 40mpg from too many petrols tbh on driving that a diesel would average 50mpg.

If you divulge your estimated annual mileage and the sort of car you are considering it would help.

annual mileage 12-15k

driving a mix of long spins and around town trips

on the look out for a mid sized sedan something like a ford focus, volvo s40 toyota corolla/auris

budget 10k or thereabouts

has to be a 1.4-1.6 for me try and keep my insurance costs down a bit as I have no no claims bonus

Nissan doctor

aidanki wrote: »

annual mileage 12-15k

on the look out for a mid sized sedan something like a ford focus, volvo s40 toyota corolla/auris

budget 10k or thereabouts

has to be a 1.4-1.6 for me try and keep my insurance costs down a bit as I have no no claims bonus

What kind of driving are you doing though? If its mostly city/urban driving or shorter trips then you will not get any benefit from the diesel.

The MPG figures you are quoting will only be possible from constant speed motorway cruising.

I would also do some research into maintenance issues with using modern diesels for short trips etc.

vectra

Nissan doctor wrote: »

What kind of driving are you doing though? If its mostly city/urban driving or shorter trips then you will not get any benefit from the diesel.

The MPG figures you are quoting will only be possible from constant speed motorway cruising.

I would also do some research into maintenance issues with using modern diesels for short trips etc.

I know you know your stuff but to be fair I do get decent mileage out of my diesel around town

Almost 100% stop start journeys now as I was also doing in my Cordoba 1.4tdi as well,


Was getting well over 700 kilometers to the tank with the cordoba, 45 litre tank.
I would never leave the tank run dry.

700 / 40 = 17.50 to litre * 4.54? = 79.45 k per gallon = 49.6 mpg. That is excellent around town. I do not see a pterol doing that


Current car = Octavia vRS tdi 2.0 litre. can squeeze 700 ish around town
55 litre tank again would never leave it run dry

700 / 50 = 14 * 4.54 = 63.56 k per gallon = 39.7 mpg

I consider that excellent mileage

Only a modern petrol engine would come close to that.

Wetbench4

Don't you also run the risk of having to change your dpf filter in your diesel? Heard they cost a few quid.

Nissan doctor

vectra wrote: »

I know you know your stuff but to be fair I do get decent mileage out of my diesel around town

Almost 100% stop start journeys now as I was also doing in my Cordoba 1.4tdi as well,


Was getting well over 700 kilometers to the tank with the cordoba, 45 litre tank.
I would never leave the tank run dry.

700 / 40 = 17.50 to litre * 4.54? = 79.45 k per gallon = 49.6 mpg. That is excellent around town. I do not see a pterol doing that


Current car = Octavia vRS tdi 2.0 litre. can squeeze 700 ish around town
55 litre tank again would never leave it run dry

700 / 50 = 14 * 4.54 = 63.56 k per gallon = 39.7 mpg

I consider that excellent mileage

Only a modern petrol engine would come close to that.

But looking at nothing but the fuel economy figures will not be making an informed decision about which suits the OP's needs IMO.

The old tech diesels are(pre common rail) are well able for short journeys compared the latest generation of engines.
Its more about the maintenence/care requirements for running a modern diesel for lower mileage/urban use then just blindly looking at the fuel economy.

Modern common rail, dpf, dmf fitted diesels are designed to give all their major benefits during high mileage motorway type use. DPF fitted cars are simply not designed for exclusive city use.

I'm just trying to expand the OP's information on the subject as the people who blindly run out to buy modern diesels saying 'it does better MPG, so will cost me less' will very often be worse off in 3 years, not better off as the OP expects.

Injector/dmf/dpf/turbo etc failures are not guaranteed as some will try to scare monger, but they are much more likely and are also all system that the equivalent petrol engine will not have. And if only one of these items fails on a diesel engine, it could push the OP's break even time from 3 years to 5 years!

vectra

Wetbench4 wrote: »

Don't you also run the risk of having to change your dpf filter in your diesel? Heard they cost a few quid.

It doesn't bother me anyhow as I allow the car to "stretch it's legs" occasionaly to clear the cobwebs

vectra

vectra wrote: »

............... 45 litre tank.
I would never leave the tank run dry.

700 / 40 = 17.50 to litre * 4.54? = 79.45 k per gallon = 49.6 mpg. That is excellent around town. I do not see a pterol doing that


Current car = Octavia vRS tdi 2.0 litre. can squeeze 700 ish around town
55 litre tank again would never leave it run dry

700 / 50 = 14 * 4.54 = 63.56 k per gallon = 39.7 mpg

I consider that excellent mileage

...............

There's a decent chance those figures are well off (10 to 15%) as you're presuming you are using the full tank less than 5l in both cases for your calculations, that's a very very crude method of calculating mpg.

vectra

RoverJames wrote: »

There's a decent chance those figures are well off (10 to 15%) as you're presuming you are using the full tank less than 5l in both cases for your calculations, that's a very very crude method of calculating mpg.

Actually I use my old receipts to check how many litres was used to fill up after clocking up the mileage so figures are very accurate,

If you wish I could do a full Accurate calculation on both cars to see what they averaged over the period of owning them

vectra

vectra wrote: »

Actually I use my old receipts to check how many litres was used to fill up after clocking up the mileage so figures are very accurate,................

Well if you specified that in your above post I wouldn't have commented

vectra

RoverJames wrote: »

Well if you specified that in your above post I wouldn't have commented

No problem,
I keep all my documents for several years :P
Just a habit of mine

aidanki

Nissan doctor wrote: »

What kind of driving are you doing though? If its mostly city/urban driving or shorter trips then you will not get any benefit from the diesel.

The MPG figures you are quoting will only be possible from constant speed motorway cruising.

I would also do some research into maintenance issues with using modern diesels for short trips etc.

2 v long spins at the weekend of greater than 90miles each week. the rest is short around town trips 2-3miles average each time.