Thank you for contacting Porch. First, if your system is 30+ years old you might consider replacement as newer technology is much more efficient and safer, regardless of fuel used. If your system is oil burning it must be serviced annually or it will not perform well, and you risk smelly failures. A fuel gas system would need filters changed, probably control adjustments and other minor items. Electric is about the same. If you need more specific information please provide the make, age and fuel type of system you have and if warm air furnace or hot water (hydronic). Should you need to locate a local pro, try the below link to input your zip code or call us at 1-855-707-0141 to get started. https://pro.porch.com/near-me/hvac-companies