Petrol or Diesel?

snow hope · Post by **snow hope** » 08 Aug 2006, 08:55

As time goes by and depletion starts, will petrol or diesel be easier to get?
Which is refined more easily from heavy sour oil?
Is the difference in price due to refinery costs at current mix volumes?
Will the price gap become greater?
Of course, I am aware that current cars get about 10 mpg more from diesel.

The reason for my questions is that I am trying to advise people who want to buy a second hand car. And yes they do need to change their current 9 year old machine. And no they can't do without a car currently.

Thanks in anticipation.

isenhand · Post by **isenhand** » 08 Aug 2006, 10:01

Only 9 years old? Still go a few years in it yet!

I would go for diesel, if the worst comes to the worse you have the possibility of making your own or using vege oil.

PS_RalphW · Post by **PS_RalphW** » 08 Aug 2006, 12:07

Obviously on the surface diesel seems the right answer - easier
to convert a diesel car to run on biodiesel or veg oil than a petrol
car to run on ethanol, and more efficient.

However, they are created from different fractions when the oil is
being refined, so each barrel generates some petrol , some diesel and
some other products. By adjusting the refining process you can
adjust the ratios to some extent, ie. more petrol or more diesel, but
they are not fully interchangable.

Diesel cars have become so much more common in Europe, that the
refineries are struggling to meet demand for diesel fuel, and when
oil gets short diesel is going to get short before petrol in many areas.

I'm sure there are more knowedgable people on this site who can give
a more definitive answer...

Post by **mikepepler** » 08 Aug 2006, 21:45

As far as I know, diesel is a simpler mix of chemicals than petrol, but as RalphW mentioned, there may be a supply imbalance in Europe. I'd go for diesel because it is more fuel efficient, and you can convert to veg oil which is readily available. If you have petrol, I don't know what would be involved in converting to ethanol, but even if you do, you can't exactly buy it neat for a low price!

p.s. usual caveats about ethics of "food vs fuel", availability if everyone does it, and the need to get rid of our cars soon anyway...

Cycloloco · Post by **Cycloloco** » 09 Aug 2006, 01:07

RalphW wrote:
Diesel cars have become so much more common in Europe, that the
refineries are struggling to meet demand for diesel fuel, and when
oil gets short diesel is going to get short before petrol in many areas.
...

It's impossible to answer this reliably.

Diesel engines cost more, are heavier, last longer and give better mpg.
Petrol will be extended with butanol, not ethanol, (my guess) in future.
Diesel was kept cheaper when the gov't wanted to promote it. Now it is too popular in Europe and costs more.

Answer: suit yourself. It is anyone's guess.

Andy Hunt · Post by **Andy Hunt** » 11 Aug 2006, 15:16

Diesel.

We've got biodiesel (in small quantities), and don't forget diesel from coal liquefaction - could be massive. And if all else fails - straight veg oil.

AFAIK, you can't put ethanol or methanol straight into a petrol engine.

Philip W · Post by **Philip W** » 16 Aug 2006, 09:28

What about converting a Petrol car to LPG instead?
You then have the choice of two fuels if supply becomes restricted.

During the fuel tanker strikes a few years back there were no queues at the LPG pumps.

It is half the cost of petrol and diesel, better for your engine and more environmently friendly.

When you get rid of your LPG car you can take the kit and gas tank out and have it put in your next car saving you ? on your next conversion.

What more could you ask for?

snow hope · Post by **snow hope** » 16 Aug 2006, 11:47

That sounds good - why aren't more people doing it?

What are the drawbacks?

Philip W · Post by **Philip W** » 16 Aug 2006, 12:08

The drawbacks are that you have to pay for the conversion up front ?1,900 and you will only see the payback over time. I calculate a petrol car costs around 12p a mile and LPG around 6p. You have to do over 31,000 miles to break even.

Most people don't want to pay that kind of money up front even if it means halving their fuel bills in the future.

If you move the kit to another car you would pay ?650 which means your payback would only be after 11,000 miles.

Another drawback is not every garage has LPG. However there are LPG finders on the web which is very useful when travelling around the country.

Post by **mikepepler** » 16 Aug 2006, 13:19

And a bigger drawback is LPG is still oil-derived, so whilst saving money, it's not doing anything to reduce dependence on oil.

Philip W · Post by **Philip W** » 17 Aug 2006, 09:24

I thought LPG was a by-product of oil production and refining (the stuff that we used to see being burnt on oil rigs or in refineries). So in response to the question Petrol or Diesel, I still think LPG beats them hands down on both environmental, price and energy supply grounds.

Clearly an electric car powered by an array of PV cells would be a better answer though!

Post by **mikepepler** » 17 Aug 2006, 11:21

Philip W wrote:I thought LPG was a by-product of oil production and refining (the stuff that we used to see being burnt on oil rigs or in refineries). So in response to the question Petrol or Diesel, I still think LPG beats them hands down on both environmental, price and energy supply grounds.

I don't think it's a by-product, Wikipedia says it's made of a mix of propane/butane/etc: http://en.wikipedia.org/wiki/Liquified_petroleum_gas
These are useful in their own right as heating fuels, and I imagine for synthesis into more complex chemicals.

Philip W wrote:Clearly an electric car powered by an array of PV cells would be a better answer though!

True, or better yet, no car at all!

Andy Hunt · Post by **Andy Hunt** » 17 Aug 2006, 14:12

Post-peak mudguard sticker:

"My other bike is a horse"