Typically like most things, gas oil prices are also influenced by supply and demand. When gas oil suppliers purchase gas oil in the summer months, because of the demand this often drives gas oil prices higher. In the winter where there is more reliance on other fuels there is less demand for gas oil suppliers to purchase this fuel. Gas oil prices are influenced by the oil prices futures. As this is traded as a commodity, gas oil prices change on a daily basis.
There are 12 countries that produce 46% of oil to supply to the world. OPEC regulates not only the supply but they can also influence the price of gas oil. OPEC aims to keep a barrel of gas oil to $70 USD. In the US, contained within a reserve known as the strategic petroleum reserve there are over 700 million barrels of gas oil stored for emergency uses. Typical examples where reserves would be called in is disasters such as hurricanes and earthquakes.
There are agreements known as oil futures or futures contracts. These allow for the buying or selling of gas oil at a specific date and specific price in the future. The process involves traders bidding on gas oil prices based on their forecasts of supply and demand of what they think the gas oil will trade at. If traders feel that gas oil prices are going to be elevated they will bid the gas oil prices upwards. Even if there is large amounts of gas oil readily available these forecasts can still cause a hike in gas oil prices.
If you are looking for cheap gas oil and want to evade fluctuations in gas oil prices then you need to find a national or local gas oil supplier and setup a fuel management scheme. By setting this up with them you are building a working relationship with them. The fact that you are purchasing gas oil from them on a regular basis means you will be less subjected to the fluctuations in the forever hiking gas oil prices as they will want to keep you as a customer.
There are many national and local gas oil suppliers in the UK that these fuel management schemes can be setup with. Many fuel companies offer an exceptional service from taking the order to delivering the fuel and offer good technical advice.