Petrol or Diesel? Your opinion matters.

[DieselE]

I had the privilege of engineering this diesel in August. It only did 9mpg but then it also did over 350mph. Diesel technology is advancing at a much greater rate than petrol. I would not try to keep up with that speed on the road, but I would with the technology and I am getting over 40mpg from my diesel Mercedes...

I am as envious as hell. A lot of us start our careers as engineers hoping to be involved in something great. Actually being involved only comes to very few.

 

[Dieselman]

I think Dieselman may have been drinking at the office party ...16 mpg indeed.
Using the tank to tank method I got 24 mpg over 1 year running a BMW 740i, an old 4 litre V8 in a heavy 1800 Kg body. I do lots of short 2 mile trips into my local town and the occasional 160 mile trip up to London.
My C180 comes in at around 35 mpg and an old diesel golf at 42 mpg.



adam

I've read a few replies saying I am wrong and quoting full tank and intermediate length journeys. Please don't think I am singling out this post.
Please remember we were supposed to be talking about journeys of upto 3 miles from a cold start.

As the information from Bosch shows the consumption is 4 x for the first kilometre and gradually gets better.

I have only extracted the information, not generated it.

Can someone who drives a petrol engined car please perform a proper study of journeys of no more than 3 miles so we can have some data as opposed to conjecture over much longer mileages.

My wifes previous car used on the same trips she does now used to average approximately 30-32mpg, she now has a heavier diesel car and averages 47-50mpg for exactly the same journeys.
This is just an example.

 

[Dieselman]

I reckon on 1 mile to a mile and a half is my car's norm.

This is a clear indication of lack of efficiency.
The longer a car engine takes to warm up the better the efficiency as the engine is converting more of the fuel into motive force and less into wasted heat.

Figures I've seen elsewhere usually say the car consumes double when cold which fits with my experience.

Is this for regular sub 3 mile journeys or longer journeys?

There is still a £500 saving to be made per annum given 6000pa and 43mpg diesel, 22 mpg petrol, which Bosch dispute.

 

[Dryce]

This is a clear indication of lack of efficiency.

Yes ....

But it doesn't exactly support your rather unrealistically extrapolated numbers

Is this for regular sub 3 mile journeys or longer journeys?

It doesn't matter because it's just the first mile to a mile and a half of *any * journey that involves a cold start.

There is still a £500 saving to be made per annum given 6000pa and 43mpg diesel, 22 mpg petrol, which Bosch dispute.

I have never seen 22mpg out of any reasonably sized petrol car! You're extrapolating some Bosch numbers you quoted which don't appear to have any bearing on the real world.

You might also refer back to my original reference to the 6000 miles which didn't refer to 6000 miles of sub 3 miles journeys. Also lots of short hourneys doesn't necesarily the same number of cold starts. Some will be follow on journeys.

 

[Robbo]

Can someone who drives a petrol engined car please perform a proper study of journeys of no more than 3 miles so we can have some data as opposed to conjecture over much longer mileages.

Whats the point though? It is a totally unrealistic scenario. Who only ever does 3 mile journeys from cold and nothing else? Nobody.

Thats why I think your estimated costs for petrol v diesel engines over 6000 miles pa are unrepresentative of the real world. If you want to use an mpg number for a petrol engined car doing 6000 miles pa with plenty of 4 mile short trips from cold (2 per day), use my C320 long term average of 25 mpg. A more reasonable sized engine would be a lot better!

Yes diesels are cheaper than petrols to run, but it's not as extreme as you suggest.

 

[Aletank]

I do 6-8000 miles per year, mostly 4-5 mile journeys and average 21/22mpg from my C200 Auto,.

 

[Dieselman]

Whats the point though? It is a totally unrealistic scenario. Who only ever does 3 mile journeys from cold and nothing else? Nobody.

Because the original post was about a car doing nearly all 3 mile journeys with occasional holiday commuting.
Bosch carried out their testing under lab test conditions and had the posted result. I supect this is somewaht more scientific than your average consumption as posted.

Thats why I think your estimated costs for petrol v diesel engines over 6000 miles pa are unrepresentative of the real world. If you want to use an mpg number for a petrol engined car doing 6000 miles pa with plenty of 4 mile short trips from cold (2 per day), use my C320 long term average of 25 mpg. A more reasonable sized engine would be a lot better!

Please see the previous post which indicates 21-22mpg for a C200. A C220 CDi would average 42-44 over the same journeys.

 

[Laters]

I'm with Dieselman on this one.
I used to get 19-21mpg around town from my c200.
I now get 35mpg from my c250td & that's taking advantage of the extra power from the 250td engine.
I have no doubt that I could easily get it to nearer double the mpg of the c200 but the power & sound of the car are preventing that for now