[Squintstream]

The father in law and I worked out the rough costs of my 335i and how long it would take before it would make better sense to be driving a diesel.

Here's the workings:

My current 335i cost approx 21k and to buy a diesel with the same spec would work out about 3k more, due to the higher residuals of a diesel.

In my previous 335d I was averaging 37 MPG and in my current I'm averaging around 27 MPG.

Diesel in my area works currently works out around £0.08p more per litre vs. petrol.

Finally, road tax costs are basically irrelevant due to the minimal differences of £10 per annum.

Therefore:

Petrol pence per mile = 27MPG/4.54 Litres in a Gallon = 5.95 miles per litre
£1.35 per litre/5.95 miles per litre = £0.226 per mile

Diesel pence per mile = 37MPG/4.54 Litres in a Gallon = 8.15 miles per litre
£1.43 per litre/8.15 miles per litre = £0.175 per mile

This means the 335i is costing £0.05 per mile more in fuel.

So, £3,000/£0.05 = 60,000 miles. Indicating I'd have to do over 60,000 miles before I'd see any gains and as I only travel around 18,000 PA, I won't see any benefits for 3 years I plan to keep it.

Now, am I missing anything? Or do you concur with my workings? I suppose the only thing I haven't taken into consideration is the lesser depreciation (over 3 years) on a diesel.

Thanks,


Charlie

[AlanQS]

I think you've got it about right. The only real unknown is how much more you would get for a diesel. If end sale price was still £1,000 more than for a petrol then you should work your calculations on £2,000 and not £3,000 so, in truth, you would get your money back around the 40,000 mile mark - so over two years in your case.

Finally, offset the extra enjoyment (assumed) of the petrol over a diesel which after all has some sort of value, to estimate which choice suits you best.

[makkan00]

Good caluclations.
Have you included the insurance prices in that?
Considering diesel cars are cheaper to insure, it changes your calculations to some extent.

[Danny.B.]

Thats an aye opener!

Although that said, my 330d is doing 50.4mpg at the moment

[Gibbo]

Charlie, I got around 37mpg from my 335d so if you can get 27mpg out the petrol I would say your are about right.

Depreciation and changing a car will always be the bigger costs in motoring. It's the 'Psychological' cost of spending £100 every time and it not lasting as long as you would hope which could wear you down over time.

You now have the facts and that should not cause you any issue. If you want to work this to your advanage there are some great M3 leasing deals at the moment.

[Hotcoupe]

Originally Posted by Squintstream

Diesel in my area works currently works out around £0.08p more per litre vs. petrol.

Funnily enough the difference in price was the exact opposite (diesel cheaper than petrol) when I bought my first diesel car (E46 330D) back in 2003.

The days of diesels being more cost effective over a petrol equivalent are a distant memory, and your workings out demonstrate it so well.

The only thing keeping the price and depreciation of diesel cars higher than petrols is people's misplaced perceptions that diesel cars are cheaper to run.

No longer the case unfortunately,unless you regularly drive long distances.

Next car for me will be a petrol,probably a 335i,a better soundtrack and far more tuning potential.

I'll live with the missing torque,and enjoy the extra horses

[MEGA]

Consider one extra factor which is premium fuel.

I don't know if you ALWAYS put premium in your 335i: But I would in your shoes. Wheras I abuse the crap out of my derg. Any fuel will do. I don't feel it makes any difference to the way the car drives or how it feels / the mpg it achieves etc.

This makes the difference just 2p/litre which is a sizeable difference.

Regardless of that though.. We discussed this in some length on EvoTechnik last month.. It happened to be days before I committed to buying a diesel, so I'd done some crunching.

I calculated out my own situation and found the break even point to be much sooner.

Below.

[MEGA]

In short Teddy the answer is not yet. But we aren't that far away either.

I was looking at this with regard a 335d. As you guys know I like to crunch numbers so I'll share. Some of this is new, some I had before.


So. I've been led to believe that the 335d is approx 5mpg more economical around town than 335i.

For instance I would get 23mpg instead of 18.

4.55 litres per galon so this means:

335i: 3.95 miles per litre
335d: 5.05 miles per litre.

Therefore a 70 litre tank will get you:

335i: 276.5 miles
335d: 353.5 miles.

And that 70 litres will cost you:

335i: £93.45
335d: £98.84

Or to put it another way, a cost per mile of:

335i: 34p
335d: 28p.

So the diesel is still cheaper.

But let's assume even on a 3 year old model the d engine carries a £1500 premium.

so for instance the i will cost 17k and the d £18,500.

It would take 25,000 miles before you break even. IE not untill you've done 25k in either of the cars will the diesel be worth the same.

If you plan to put more than 25k miles on the car then the outlay is worth while.


...But it's not quite that unreasonable...

The diesel engine is likely to retain it's higher value when you sell the car.


If you factor that in and say general depreciation means the gap will close in from the 1500 I expected at a 3 year old car (bear in mind its 2300 or so on a brand new model between the top petrol and top diesel 3 series): down to 1000,

Then the mileage you need to break even is just 16,700. And any further miles beyond that is profit for the diesel driver.

If you argue most people keep their cars for 2 years then that is just 8,350 miles per year. Not at all unreasonable. Quite below average instead.



So for me, diesels are still worth purchasing: Although only when we're comparing performance models. The fact is there's no reason to get a 2 litre diesel over a 1.4 litre turbo charged petrol if economy is your only concern: The diesel will be alot more fun after a remap still, but you'll never break even: Especially buying new. However the premium between comparable 6 cylinder engines means for most people the diesel will still work out cheaper. The numbers change every month depending on depreciation and mileage but I still think it's worthwhile.

Of course if that disparity raises by another 6p at the pump: My maths goes out the window. At that point you'll never break even.

[MEGA]

My calculations were based on 1.33/litre versus 1.41/litre by the way.

[Gibbo]

Originally Posted by Hotcoupe

Funnily enough the difference in price was the exact opposite (diesel cheaper than petrol) when I bought my first diesel car (E46 330D) back in 2003.

The days of diesels being more cost effective over a petrol equivalent are a distant memory, and your workings out demonstrate it so well.

The only thing keeping the price and depreciation of diesel cars higher than petrols is people's misplaced perceptions that diesel cars are cheaper to run.

No longer the case unfortunately,unless you regularly drive long distances.

Next car for me will be a petrol,probably a 335i,a better soundtrack and far more tuning potential.

I'll live with the missing torque,and enjoy the extra horses

Ian, sounds good and makes sense now to go to Petrol if you are not doing mega miles. The reality is that Europe never built the capacity for the diesel volumes we currently have and hence the premium vs petrol.

The next generation performance Petrols 328i, New VW Golf GTI will be heading for 40mpg+ in daily use and therefore become a valid option.

[Kerr]

As everyone has noticed diesel has increased in price much quicker than petrol over recent years.

This will continue to happen at an accelerated rate making the mileage required to make back the difference even longer.

How many people on this site will cover 60,000 miles anyways?

[ed335d]

I had thought about doing the calcs when I changed from the big D to the M, but the rush of blood from the brain to my gentlemen's area when I'm driving makes me forget all about it.

[MEGA]

Originally Posted by ed335d

I had thought about doing the calcs when I changed from the big D to the M, but the rush of blood from the brain to my gentlemen's area when I'm driving makes me forget all about it.

Haha.

Is this the famous "fizz behind the penis" that James May always talks about ?

Personally seeing mid to high 20s mpg on the motorway and low teens when driving it properly given the mileage you do Ed... I couldn't bear it.

Then again I drive like a f*cking moron most of the time so wouldn't ever be able to calm down and conserve fuel, etc.. Heh

(So far 22 to the gallon over 800 miles in the D)

[225_AB]

I enjoy having to fill my car less often, I prefer the torque of the diesel engine. From a financial point of view I could have bought either a diesel or petrol and I chose the diesel because of its driving characteristics. Will probably have another petrol in the future but with a BMW 6 pot diesel for now and another one (640D) ordered for July gonna stay in the diesel camp for now. Also of you drive in Europe (we go to France once a year) diesel is cheaper than petrol.

[m1bjr]

Nobody considering servicing costs then?

Must be higher on a petrol, especially given its appetite for plugs, HPFPs, coilpacks and injectors?

Worth bearing in mind!

[ed335d]

Originally Posted by MEGA

Haha.

Is this the famous "fizz behind the penis" that James May always talks about ?

Personally seeing mid to high 20s mpg on the motorway and low teens when driving it properly given the mileage you do Ed... I couldn't bear it.

Then again I drive like a f*cking moron most of the time so wouldn't ever be able to calm down and conserve fuel, etc.. Heh

(So far 22 to the gallon over 800 miles in the D)

Not sure I'd describe a semi as a 'fizz behind the penis'

That's terrible mpg for the 335 Dave, you're obviously driving it right

My mileage has really dropped recently, due to project work in London. I only did about 10k last year compared to 18k the year before. Only spent £240 on fuel so far this year, which is nice.

[MEGA]

Originally Posted by ed335d

Not sure I'd describe a semi as a 'fizz behind the penis'

That's terrible mpg for the 335 Dave, you're obviously driving it right

My mileage has really dropped recently, due to project work in London. I only did about 10k last year compared to 18k the year before. Only spent £240 on fuel so far this year, which is nice.

Good news that..

240 for 9 weeks of driving! That's incredibly good going really..

Shame Will's not about to "pick up" on your semi comments.. He's more experienced at taking such things.

[Mart1000]

Originally Posted by Danny.B.

Thats an aye opener!

Although that said, my 330d is doing 50.4mpg at the moment

Do what? F**k me sideways that's good!

I average 45mpg on way home up the M11.

[Danny.B.]

Originally Posted by Mart1000

Do what? F**k me sideways that's good!

I average 45mpg on way home up the M11.

Ive been doing alot of mileage randomly trying to get my DPF to regen, two bouts of 100mile+

Normally sit at around 45mpg on my daily 13mile (each way) trip to work which i think is bloody good going!

And i wouldnt exactly say i drive like Mrs Daisy

But all within the restraints of the law you do understand Mr Officer

[Squintstream]

Yeah, depreciation, servicing and insurance are all good points that you should include within the calculations if you're seriously trying to weigh up which engine is best for your needs.

I really did it for fun. But having driven the new petrol car for a month I couldn't be any happier, the sound has got to be worth 2p a mile

Not tried the premium unleaded, so may have to fill up with that next time and see how it goes.

All in all though, it seems you have to drive quite a few miles before the diesel makes sense. Unless you drive like Mega with his lead lined boots

[CarAbuser]

The 335d is not the most economical engine, the 330d seems to offer much better economy for little power sacrifice.

Am I right in thinking the 335d is still the old engine where the 330d is completely new block?

[MEGA]

It's a BIG power sacrifice mate

50bhp is only slightly less than your average hatchback has in total and is still 30% more power. Not "little".

And that is before you remap