Oil tanker routes are relatively fixed in the same way that dry cargo, grain carriers or container vessels maintain shipping route. Many shipping companies have several different vessels which are assigned to different routes that are predetermined by the cargo suppliers and consumers. Oil tankers chartering companies also play a big role towards maintaining oil tanker routes over long periods and it is rare to find vessel that sail the open sea just haphazardly without knowing of the next destination and cargo they will be sailing to.
Oil tanker routes could be compared to conventional land transport that most people are used to using and have more knowledge about, if one is observant it is rear to find a transport vessel that constantly changes it route. This is simply because it is time consuming and unpractical over long term since there is instability of the cargo that will be transported since the chartering companies will only deal with a shipping company that will ensure the timely delivery of customer cargo.
Only by maintaining a constant rout can a shipping vessel of any kind is able to secure stable cargo thus income to be able to sustains itself and create profits. Since the vessel is mostly out at sea they rely on the chartering companies to handle most of the land based affairs. Even the largest of the companies that have offices in many countries cannot be able to employ and manage all the people involved in collecting and planning a vessels cargo. Some cargo vessel ships like oil tanker do not require many chartering companies or agents for their cargo but even oil tanker routes are mostly predetermined since the few chartering companies book the vessel only if they are able to uphold punctuality and commitment to a chartering company.
Shipping companies must maintain determined route but in the same way that the shipping companies uphold this promise the chartering companies are also expected to uphold there side of the bargain by providing a full load or a fixed price for any shortfalls. Having this partnership helps safeguard both parties who could either benefit or loss but would impart both in the same ways.
Oil tankers are specialized marine vessels meaning that cannot load any other cargo besides petroleum produces and it is a rather one sided issue since some countries proves while other consume and the vessels are empty half the trip while going back to the supplying nation to load. Mostly tanker vessel have this privilege of voyaging empty but other cargo carriers like grain or container vessel always have a hefty load waiting for them and as soon as the offloading is done the loading begins.
Oil tanker routes and routes used by all marine vessels are predetermined and booked in advance and even if a vessel owner is planning to change the route, advance notice must the provided to the oil tanker chattering companies and suppliers to prepare them in advance for another vessel. Abruptly changing the vessel route is not possible unless for some emergency and if a vessel did try without following the correct procedure that it could result in boycotts from chattering companies on the route the vessel plans to move to until the damage costs are paid to the chattering companies affected.