BE VERY VERY AFRAID OF OIL BOILERS, TANKS AND LINES!
An Oil leak is a catastrophic event which will have major structural, financial and psychological effects on you, your house and your neighbours!
I know from experience! Such an event has taken years off of my life...
Be certain that your home insurance is correct and that it covers you adequately for escape of oil.
Only employ a certified and INSURED Professional to service the boiler etc. Always get a receipt and a report/cert from them after each visit.
Never let a tenant, neighbour or oil delivery truck driver "bleed" a burner. (fit a Tiger loop)