Unleaded Vs Diesel

steve-L

The calculators don't mean much....
If you ignore purchase price for now then Joe's calculation shows a reasonable calc.
If you include purchase price then you also need to include depreciation, service (including DMF) over the time you own the car.

The DMF is looked at like a fixed item whereas its more like a replaceable part... the clutch/DMF can be looked at like pads/disks... sometimes you only need to change the pads and sometimes pads and disks.

So my Honda got 111,000 from the first clutch and 180,000 from the first DMF.
The DMF is attached to the clutch, they need to take it off to replace the clutch.... so labour is identical.
For example:
Changing the clutch is 25% part and 75% labour
Changing the DMF & Clutch together is 50% part and 50% labour.

Reality is clutch costs about 150-200 and a DMF about 400-500 but the labour is likely £600-£1000 on a FWD car (depending which car and labour costs of garage)

Real question is comparing diesel and petrol and to be honest this is like comparing a motorbike and a car.
How do you compare?
You could start by looking at the same model of car but with the same combined MPG.
Hence you are looking at say a 1.2 or 1.4 petrol vs a 1.9 TD
Another way is to say I have £X,000, that buys me say a older BMW 320D/Octavia 1.9TDi or newer Fiesta 1.2 and they get similar MPG on extra-urban... then its which do you prefer to drive?
Its quite surprising what you can get on a £/£ basis in an older diesel.
The 1.2 Corsa/1.3 Fiesta will probably on average not make 100,000 miles... some will... most won't. The BMW or Skoda should make 500,000 miles.... they will need some parts along the way like the clutch/DMF but there is no reason the engine properly looked after shouldn't make half a million. If you like your car and its not costing too much to maintain then keeping the diesel for 100,000 miles will doubtless be a LOT cheaper than changing the Fiesta/Corsa frequently and in most situations be a nicer car to sit in. (IMHO)

In simple terms if you do mostly longer journeys especially on A roads and motorways then the diesel will get better MPG and be more stable on the motorway .... if you do mainly 1-2 mile journeys to the local shop then the diesel will never warm up, run at lower MPG, damage the DPF etc.

Hence as I said, you are comparing cars as different as a car and motorbike in many ways. Even the same model but a small petrol vs bigger turbo diesel .....

If you buy a non-turbo diesel then its how long the rest of the car lasts...

So you need to decide what type of driving you do.... what you like to drive and how long you will keep the car. If you mainly do 1-2 mile trips then the answer is IMHO simple and a small eco petrol... if you do mainly motorway/NSL roads then the diesel and somewhere inbetween.... a lot of preference for what you would prefer to drive.