With legislation constantly changing in regards to oil tank siting and specification your tank may not be up to standard this more often than not is overlooked but could invalidate various insurances in the event of a fire, so if you think that your tank isn't up to standard it may pay off to get it moved or install a new one altogether, having said that as your tank ages the likely hood of an environmental incident increases so regular inspection of your tank to ensure its of good working order is a good practice to protect yourself against an oil spill and a negative unwanted and unnecessary environmental impact.