When does buying diesel become more economical?

Briando

Reading the forums for a while, I see a lot of people saying they want a diesel because of the cheaper fuel price and better mpg.. so lower running cost.

Diesel tends to be in a lower tax bracket also.

Petrol : Cheap initial Price , more expensive to run.
Diesel : More expensive initially, cheaper to run.

Looking at 2L engined cars, in the year 2009 (Audi A5 for example)

There is a diesel is about 3000 more expensive.

If I keep the car for 5 years, doing 250km per week how do you calculate when its better to go with the 3k initial saving and get the petrol, or invest in the diesel.

Cormac2791

250km x 52weeks = ?

? X 5years = ?

? X €pricefuel = answer

conzy

250km certainly isn't diesel territory, I do well over 250km a week in a 325i and I manage just fine and I'm only a young chap

250km a week is only ~8000 miles a year! Id say 3 times that is getting into diesel territory..

Anan1

You work out your fuel costs in petrol over the period, do the same for diesel, and subtract one from the other to get your savings. Factor in servicing, maintenance, , tax and insurance differences too. You then work out how much more the diesel car will cost to own than the petrol car, ie purchase price less resale value for both.

ShadowHearth

Diesel will cost you more initially and it will cost you more in repairs then n/a petrol car.

250km a week is not that much. Is that city driving mostly? If it is, them getting a diesel won't even save you that much on refills too.

Blazer

At least 20,000 miles a year.
By the time you factor in turbo replacements, DPF replacements you'd need to be doing at least that mileage for it to be worthwhile.
I do around that a year and save about €1500 on diesel over my last petrol car.
However if the turbo/dfp blew on my car that would instantly wipe out any savings I did make.
My car also increased by about €200 and since it's a BMW service costs are higher thus very nearly wiping out what I saved over my petrol car.

In fact depending on whether your car has a warranty or not, I'd say based on the above if no warranty you'd want to be saving a minimum of 2/3 grand a year over petrol in order to switch.

Mycroft H

Fuel PA

2l A5 Petrol FSI (180Bhp) = 39MPG.
2l TDI (177BHP) = 61MPG

Average price per litre of petrol
159.9c

Diesel
149.9


Cost PA in fuel alone

Petrol: 155m@39MPG= E1502
Diesel: 155m@61MPG= E900.64

Tax band:

Petrol @ 161g/km = E481 PA
Diesel @ 120g/km = E160 PA

There is a saving of E903 PA by choosing the diesel over the petrol based on fuel and tax.

The maintenance and insurance are figures you yourself are going to have to calculate. Depreciation is going to be a big factor too, the petrol is going to depreciate a hell of a lot quicker then the diesel.

Briando

The whole service cost things make me wonder.

Owned a Toyota D4D for the last 5 years and had it repaired once for 800Euro and only other times(twice) it went in was to be checked before the NCT which was tire change and oil etc. Not expensive.

Diesels cost that much more to maintain/service for what reason? Needing to replace the turbos? Are there other reasons? I'm ignorant of the service differences between petrol and diesel.

Mycroft H

Briando wrote: »

The whole service cost things make me wonder.

Owned a Toyota D4D for the last 5 years and had it repaired once for 800Euro and only other times(twice) it went in was to be checked before the NCT which was tire change and oil etc. Not expensive.

Diesels cost that much more to maintain/service for what reason? Needing to replace the turbos? Are there other reasons? I'm ignorant of the service differences between petrol and diesel.

A lot of it is down to poor Irish maintenance and less then ideal driving conditions. Diesel particulate filters need to have the engine running at a sustained temperature for a decent amount of time. Any motorway or N road driving will tick all the boxes. Town driving and short hops really do not do diesels any favors.

Lemming

BX 19 wrote: »

Diesel particulate filters need to have the engine running at a sustained temperature for a decent amount of time. Any motorway or N road driving will tick all the boxes. Town driving and short hops really do not do diesels any favors.

Somewhere around 25+ minutes at 80kph+ (or somewhere north of 2000 rpms) with a consistent speed to allow the DPF to self-clean AFAIK

Blazer

Lemming wrote: »

Somewhere around 25+ minutes at 80kph+ (or somewhere north of 2000 rpms) with a consistent speed to allow the DPF to self-clean AFAIK

Easily..for my 520D I've to hit over 75c at 3000rpm so that the DPF will regenerate.
Short trips means the DPF never gets to regenerate and starts to build up with soot/deposits leading to DPF/Turbo failure...
I normally take it for a good hard drive at least once a week to ensure it does this.
You're talking about €1200 minimum for each to replace unless under warranty.

Mycroft H

Lemming wrote: »

Somewhere around 25+ minutes at 80kph+ (or somewhere north of 2000 rpms) with a consistent speed to allow the DPF to self-clean AFAIK

I'd run with that. I get my mother to run her car in 4th for about 10 minutes at 100km/h every now and then. She does do a lot of short journeys but a large amount of long journeys too. Its the environment in which the car is driven in, not the mileage.

Briando

So going on that logic, Turbo Diesels are not a great car when you are commuting through the city everyday?

Would you be wrong to expect your turbo to last 10+ years?

Blazer

Briando wrote: »

So going on that logic, Turbo Diesels are not a great car when you are commuting through the city everyday?

Would you be wrong to expect your turbo to last 10+ years?

With just city driving? Definitely TD's not recommended for that..it takes something like 20 mins for diesel engines to properly warm up.
10 years would be highly optimistic for a turbo in city driving.

Mycroft H

Blazer wrote: »

With just city driving? Definitely TD's not recommended for that..it takes something like 20 mins for diesel engines to properly warm up.
10 years would be highly optimistic for a turbo in city driving.

I don't know what diesel your driving. My Xantia and the C5 were up to operating temp within 10 minutes.

Max Power1

BX 19 wrote: »

I don't know what diesel your driving. My Xantia and the C5 were up to operating temp within 10 minutes.

Same for my Golf (Mk4)

Mycroft H

Max Power1 wrote: »

Same for my Golf (Mk4)

Now in saying that, our old defender with the belt driven fan would not get warm during the big freeze. We taped up the front of the radiator and only then it started to get warm.

smash

Really is doesn't matter about only doing 250km per week. Bottom line is that diesel costs less, lasts longer in the tank and is cheaper to tax.

Up to you if you want to spend the extra 3k purchase price or not. And sure you might save that 3k by importing.

Blazer

smash wrote: »

Really is doesn't matter about only doing 250km per week. Bottom line is that diesel costs less, lasts longer in the tank and is cheaper to tax.

Up to you if you want to spend the extra 3k purchase price or not. And sure you might save that 3k by importing.

And that's the problem with most Irish buyers..they only see what you just said.
Have a quick read of the below link

http://www.which.co.uk/cars/driving/driver-tools/petrol-vs-diesel/choosing-between-petrol-and-diesel/

About DPFs

http://en.wikipedia.org/wiki/Diesel_particulate_filter

Idbatterim

I'm going to throw in another non cost related point, petrols are far nicer and quieter to drive than diesels... Another point on the likes of an 09 A5, forget about fuel as being the main cost, I wont even mention the motor tax (as its virtually nothing) depreciation will be several thousand per year...

firefly08

Fuel PA

2l A5 Petrol FSI (180Bhp) = 39MPG.
2l TDI (177BHP) = 61MPG

Average price per litre of petrol
159.9c

Diesel
149.9


Cost PA in fuel alone

Petrol: 155m@39MPG= E1502
Diesel: 155m@61MPG= E900.64

Tax band:

Petrol @ 161g/km = E481 PA
Diesel @ 120g/km = E160 PA

There is a saving of E903 PA by choosing the diesel over the petrol based on fuel and tax.

There is a diesel is about 3000 more expensive.

3000 / 903 = 3.32.

So, to buy the diesel and drive it for 3 years and 4 months will cost you exactly the same as buying the petrol and driving that for 3 years and 4 months...assuming, of course, that

• the difference in price between diesel and petrol remains the same for 3 years
• the difference in tax remains the same for 3 years
• both cars cost the same to service for 3 years

I think it's safe to say that this represents the best case scenario. (Although I didn't factor in depreciation; this is just cash you have to spend)

But since you can't predict those things, the question is - do you want to wait for 3 years before you start saving anything? Or just keep the 3000 euro in your pocket for the time being? I know what I'd do

Mycroft H

firefly08 wrote: »

3000 / 903 = 3.32.

So, to buy the diesel and drive it for 3 years and 4 months will cost you exactly the same as buying the petrol and driving that for 3 years and 4 months...assuming, of course, that

• the difference in price between diesel and petrol remains the same for 3 years
• the difference in tax remains the same for 3 years
• both cars cost the same to service for 3 years

I think it's safe to say that this represents the best case scenario. (Although I didn't factor in depreciation; this is just cash you have to spend)

But since you can't predict those things, the question is - do you want to wait for 3 years before you start saving anything? Or just keep the 3000 euro in your pocket for the time being? I know what I'd do

And the diesel is going to be worth more when selling it on in three years

firefly08

Im going to throw in another non cost related point, petrols are far nicer and quieter to drive than diesels...

Normally I'd agree but that VAG 2.0 diesel is pretty sweet to drive (still sounds a bit agricultural though )

ghogie91

cormacharraghy wrote: »

250km x 52weeks = ?

? X 5years = ?

? X €pricefuel = answer

When you put it like that and lets say take Diesel at 1.55 and petrol at 1.66 (guessing roughly off hand) its now that much of a saving there is it :O obviously ruling out any mpg improvments with diesel, thats a differant ball game

Idbatterim

bear in mind if you are borrowing that money, that if you go for the petrol you will also be saving money on the interest... IF one thing goes wrong with the diesel that wouldn't have with the petrol, you can probably knock at least a years worth of fuel saving off the diesel...