Price rise per litre and per gallon as the price of a barrel of crude oil rises
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When averaged, crude oil represents 42.6% of the retail price of gasoline in the USA. The same is broadly true for most countries, except that there is an overlay of tax applied to petrol sales in most European and developed Oceanian countries.
Broadly, as there are 42 US 'short' gallons in each barrel of oil, a $US1 increase in the price of a barrel of oil translates to a 2.5 cent increase per US gallon of petrol or diesel at the pump.

As 1 US gallon is 3.79 litres, a $US1 increase in the price of a barrel of oil translates to a 0.65 US cents increase per litre of petrol or diesel at the pump.

Price changes don't happen immediately - refiners and gas stations increase (and decrease) prices according to how much fuel is in stock, how much has already gone, when the next 'batch' will have to be bought in, and the change in cost to replace oil or gas in the refining system or in the storage tanks. Fast turnover countries may see 80% of their stored 'old price' petrol gone in 2 weeks, and the 'restock' fuel may therfore be charged out at the new price less 20% (representing the dilution effect of petrol at the 'old' price). Other countries with slower sales or greater storage may see prices change less frequently, but more steeply.

Retail margins are very small, and there is little opportunity for gas stations to absorb costs.

World
As oil is almost totally priced in US dollars (at the moment) the increase below will have to be converted into your own currency. Obviously, movement in exchange rates will raise or lower the price of petrol without any movement in crude prices at all. 
If your currency becomes weak relative to the US dollar the price of petrol and diesel will go up no matter how stable the oil price.
If your currency strengthens against the US dollar, the price you pay for petrol and diesel will go down, no matter the international oil price hasn't moved in any direction at all.

If the price of crude oil surges by:

$US1 add 0.65 US cents per litre to what you are paying at the pump
$US2 add 1.03 US cents per litre to what you are paying at the pump
$US3 add 1.95 US cents per litre to what you are paying at the pump
$US4 add 2.60 US cents per litre to what you are paying at the pump
$US5 add 3.25 US cents per litre to what you are paying at the pump
$US6 add 3.90 US cents per litre to what you are paying at the pump
$US7 add 4.55 US cents per litre to what you are paying at the pump
$US8 add 5.20 US cents per litre to what you are paying at the pump
$US9 add 5.85 US cents per litre to what you are paying at the pump
$US10 add 3.60 US cents per litre to what you are paying at the pump

This very rough formulaic approach can allow you see how much more you are paying now relative to a previous time (or price point).

For example, in june 2005 petrol hit $US60 a barrel. By mid august it was about $US65 a barrel. This jump is likely to increase the cost per litre by just over 3 cents (US money).

If there is a refinery bottleneck around late 2007 oil might be pushed by futures traders to the 'psychological' $100 a barrel. This jump (from june 2005 levels of $60)  is likely to increase the cost per litre by ($40, and thus 4 x the $10 increment of 3.6 cents) about 14 cents (US money) a litre.

USA

Oil is currently almost exclusively traded in US dollars. If the price of crude oil surges by:

$1 add 2.5 cents per gallon to what you are paying at the pump
$2 add 5 cents per gallon to what you are paying at the pump
$3 add 7.5 cents per gallon to what you are paying at the pump
$4 add 10 cents per gallon to what you are paying at the pump
$5 add 12.5 cents per gallon to what you are paying at the pump
$6 add 15 cents per gallon to what you are paying at the pump
$7 add 17.5 cents per gallon to what you are paying at the pump
$8 add 20 cents per gallon to what you are paying at the pump
$9 add 22.5 cents per gallon to what you are paying at the pump
$10 add 25 cents per gallon to what you are paying at the pump

This very rough formulaic approach can allow you see how much more you are paying now relative to a previous time (or price point).

For example, in june 2005 petrol hit $US60 a barrel. By mid august it was about $US65 a barrel. This jump is likely to increase the cost per gallon by 12.5 cents.

If there is a refinery bottleneck late in 2007 oil might be pushed by futures traders to the 'psychological' $100 a barrel. This jump (from june 2005 levels of $60)  is likely to increase the cost per gallon by ($40, and thus 4 x the $10 increment of 25 cents) $1 a gallon.

How can you reduce fuel consumption short of buying a motorscooter?
Gasoline consumption can be reduced by 10% to 20% by -
What is the cheapest form of motorised transport?
A bicycle with an electric engine.

Off the shelf electric motors for bicycles provide speeds of nearly 20 miles per hour on the flat. The battery is recharged from domestic supply in about 4 hours, at a cost of cents. Calculated on joules of energy expended before recharging, the motors give the equivalent of around 1000 miles to the gallon.

Solar powered trickle chargers would make re-charge essentially free.