Engine choices - higher power diesel or petrol?

[Condi]

I'm considering options for a new (to me!) car, and have a very mixed driving profile, consisting of short runs (5 miles to the gym, 12 miles to work etc) but then also fairly frequent longer runs of 150+ miles on the motorway each way. The fuel economy for the shorter runs doesn't really matter within reason, but I can't be doing longer runs at 30mpg! The x35i petrol engine figures suggest good economy on longer trips of about 45mpg which would be very acceptable, or there is the option of the diesel 330/335 engine which will be much better on a longer run, but maybe not so fun for the shorter trips? I've had diesels before and with the mix of driving it gives plenty of runs to clear out the DPF, so it doesn't massively concern me, but a petrol would be nice for a change.

Heart says petrol, head says diesel!

[steve_n]

If you can't afford 30mpg then you need the diesel. Even on a so called long distance run you'll struggle to crack 35mpg with a 35i petrol by the time you add on the non motorway parts of the journey.

[TwinExit]

If you average 27 MPG on petrol vs 40 MPG on diesel, the basic calculations based on 500 miles a week works out it will cost you approx £100 per month more in petrol than diesel based on today's typical prices per litre of petrol vs diesel.

Then if you factor in depreciation/resale and the overall cost of running the car (barring any repairs/fault fixes) the petrol option relatively is not that much more expensive to run.

[Court_S]

Personally, I’d go petrol but I prefer them to diesel’s.

The 35i engines are pretty good on a run. My old N54 will average circa 37 on a decent trek which I’m happy with. It’s sub 30 on shorter runs.

I never managed any of the crazy high MPG figures that other M140i owners managed, even on long trips.

[steve_n]

The B58 40i is a good 5mpg better on a long run than the 35i N54/55.

I'd get petrol too out of personal preference and the cost being acceptable.

However, if you're expecting more than low to mid 30s on a long run you'll be disappointed.

[Maxus]

I have looked into petrol v diesel for my next car. If it were the 40i v a 30d, with the reported economy of the 40i in a car and the fuel cost variance the difference is not great for an average mileage.

A quick calculation of 10,000 miles a year on a 30 mpg petrol v a 40 mpg diesel I calculate a c£30 a month premium for the petrol.

[Pica-Pica]

The main factor for me would not be the cost, nor any dpf risks, but simply ‘how much torque would I appreciate’.

[Court_S]

Are there any clean air zones likely to impact where you live? That’d affect my decision if it was an issue.

[bigdom]

BMW diesel starting being Euro 6 from 2012. I have petrol & diesel, both good in their own right, used for different jobs.

[Condi]

Thanks for the replies, I've done the maths and the petrol isn't as much as expected over the diesel, not least when the diesel I have does less than 40mpg!

Off to take a 435i and a M235i out for a test drive, the 435i is currently preferred as it will take a tow bar, whereas the M235i isn't approved/cant be fitted with one.

The ULEZ thing was something I had forgotten about - between Birmingham, London, Bristol and soon the Scottish towns, seems prudent to get something exempt.

[Mr Tidy]

Interesting to see costs may not be too different overall.

I think it depends on what model the engine will be fitted in as well. My daily is an E90 330i manual and most of the time I'd be just as happy with a 330d, but in an X5 for example I'd definitely prefer the diesel.

I've gone for petrol because being retired I don't do longer trips often enough to regenerate a dpf and I have family in a London Borough - I'm not sure I'd want to pay £12.50 for each visit!

[smashy]

Condi said:

Thanks for the replies, I've done the maths and the petrol isn't as much as expected over the diesel, not least when the diesel I have does less than 40mpg!

Off to take a 435i and a M235i out for a test drive, the 435i is currently preferred as it will take a tow bar, whereas the M235i isn't approved/cant be fitted with one.

The ULEZ thing was something I had forgotten about - between Birmingham, London, Bristol and soon the Scottish towns, seems prudent to get something exempt.

Diesels from 2016 are Euro 6 so fine re ULEZ my F30 30d used to do 50-54mpg on long motorway journeys once saw 61mpg going up to leicester ,never used eco. My 335d does around 48-50 mpg although once saw 58mpg on a long M4 run

[puresilk]

High powered diesel all day long.

[MikeM6]

puresilk said:

High powered diesel all day long.

Conversely, I'd say definitely petrol for this scenario. Economy on those things is seriously impressive, whereas the diesels are mostly disappointing regarding MPG. If it was a 2.0d then yeah, but it's not as though the 35d is hitting 50mpg easily, so for the slight difference you can have the nicer petrol.