Yes, fuel polishing is worth the investment as it can help prevent unexpected downtime and costly repairs caused by fuel-related issues.
The cost of fuel or oil polishing or any other service is dependant upon the work entailed and ultimately the level of contamination. As specialists we will do a preliminary sample and or survey and advise of the cost before any works therefore ensuring your not spending any more than you need to. 
To determine if oil is clean, you can visually inspect it for any cloudiness or discoloration. Clean oil will be clear and free from any suspended particles. Additionally, oil analysis tests can help assess its cleanliness.
The length of time it will take to polish your fuel or oil will vary depending upon many factors such as amount of contamination, tank type, and amount of fuel or oil to be polished. We only charge by the amount of fuel/ oil polished and amount of filters used not by the length of time it takes us. ​
Diesel bug refers to the growth of bacteria and fungi in diesel fuel. It can cause fuel degradation, clogging of filters, and corrosion in the fuel system, leading to engine problems and reduced performance. ​
Fuel polishing involves the purification and filtration of fuel to remove water, sediments, and microbial contaminants such as diesel bug. By eliminating these impurities, fuel polishing effectively treats and prevents the presence of diesel bug in the fuel system.