At the moment it looks like my job could be moving location. Currently I only live 2.5 miles away from work but my role sees me doing a fair bit of business mileage (paid at 40ppm). Whatever the outcome my business mileage is likely to decrease but my commute rise to either 12 miles a day or 60 miles a day. If it is the former my Octavia vRS will stay with me for another year or so but if I end up doing the longer commute I'll be getting rid of it.

On to my point (finally) one of the things I'd be looking for in a replacement is better fuel economy, more importantly a better fuel cost per mile which is where a bit of uncertainty sets in.

At the moment diesel is a bit more expensive than petrol but not by enough that it cancels out the big MPG advantage that diesels have over the equivalent petrol. However a few unreliable internet based sources have been saying that this is likely to change in the future as the demand for diesel continues to rise leaving an excess of petrol. Supply and demand would therefore dictate that the gap between petrol and diesel costs will continue to grow. I've heard that this could start playing a major factor in as little as 5 years.

Is this all hype and speculation or is there any weight behind this theory?

Obviously 5 years is enough time that if I had to change my car tomorrow I wouldn't let it sway my decision but it was food for thought at least.

I wouldn't worry about the possible difference in cost between petrol and diesel in the future.Most of fuel cost is tax.If a large difference occured ,the government would simply increase the tax on the lower priced fuel.To answer your question ,it would be diesel every time for me with your current mileage.You would also have better resale if the car was your own.

Just make sure you do the sums on purchase price vs MPG vs fuel savings. You may be quite suprised how long it will take you to start saving money the higher mpg diesel compared to purchasing a petrol car.

http://www.parkers.c...sel-calculator/

The petrol/diesel gap always widens in tehe winter and closes up a bit in the summer months. This is due to teh demand for heating oil which as a very similar product to diesel.

If I remeber correctly diesel production capacity in both the UK and Europe has increase lately and there further new facilities due to come on stream shortly.

I wouldn't worry about the possible difference in cost between petrol and diesel in the future.Most of fuel cost is tax.If a large difference occured ,the government would simply increase the tax on the lower priced fuel.To answer your question ,it would be diesel every time for me with your current mileage.You would also have better resale if the car was your own.

Yeah the problem I find myself with now is that I've really got a taste for turbo charged cars. They suit my driving style and what I want (and now after 3 1/2 years of owning my current car, expect) from a car. I'm not too fussed whether the thing is diesel or petrol powered so it does come down to the finances aspect.

Just make sure you do the sums on purchase price vs MPG vs fuel savings. You may be quite suprised how long it will take you to start saving money the higher mpg diesel compared to purchasing a petrol car.

http://www.parkers.c...sel-calculator/

A good point. When shopping for a car though I always set a budget and end up spending all of it. The concept of spending say £8k on a diesel or £6.5k on a petrol and keeping the rest for fuel wouldn't work for me because I'd simply end up spending £8k on a petrol car instead!

The petrol/diesel gap always widens in tehe winter and closes up a bit in the summer months. This is due to teh demand for heating oil which as a very similar product to diesel.

If I remeber correctly diesel production capacity in both the UK and Europe has increase lately and there further new facilities due to come on stream shortly.

I think this was one of the points that was raised when I was reading a little about this. Diesel production capacity has indeed increased but along with this petrol production will rise as a by product. Therefore going back to my original point, surely this would drive the petrol costs down, even though they would still be kept relatively stable due to taxation?

A good point. When shopping for a car though I always set a budget and end up spending all of it. The concept of spending say £8k on a diesel or £6.5k on a petrol and keeping the rest for fuel wouldn't work for me because I'd simply end up spending £8k on a petrol car instead!

But you'd get a much better petrol car for you money.

For example;

When I was looking for my A4 it was either going to be a 2.0TFSI q or a 3.0TDI q. I got my pristine 3yr old motor with only 16K miles on the clock for £3k less than a 3.0tdi with 55K on the clock in not as good condition. Harrogate Audi even said they'd have no problem selling the tdi and wouldn't budge on price yet would happily let me bid for the TFSI as they knew it would stay longer on the forcourt because of peoples "IMHO mostly silly" view that diesel is "ALWAYS" cheaper overall.

I can get 35mpg out of mine on a run at legal motorway speeds and it's a hell of a lot more agile in the corners than the equiv powered/performance 3.0TDI. And this is like for like real world performance comparison... infact is anything the TFSI is quicker than the TDI.

But you'd get a much better petrol car for you money.

For example;

When I was looking for my A4 it was either going to be a 2.0TFSI q or a 3.0TDI q. I got my pristine 3yr old motor with only 16K miles on the clock for £3k less than a 3.0tdi with 55K on the clock in not as good condition. Harrogate Audi even said they'd have no problem selling the tdi and wouldn't budge on price yet would happily let me bid for the TFSI as they knew it would stay longer on the forcourt because of peoples "IMHO mostly silly" view that diesel is "ALWAYS" cheaper overall.

I can get 35mpg out of mine on a run at legal motorway speeds and it's a hell of a lot more agile in the corners than the equiv powered/performance 3.0TDI. And this is like for like real world performance comparison... infact is anything the TFSI is quicker than the TDI.

I can see what you are saying and if I was considering a petrol at say £10k and a diesel at £12k then that makes perfect sense. The reality for me is that realistically I'd be considering a petrol at £6k or a diesel at £6k :p The only thing that might change is that the Diesel might be a year or so older and therefore I might want to get rid of it quicker but I think I'll end up keeping whatever I bought for 3 to 5 years by which time my priorities will probably have changed again so it isn't really an issue.