KevCnew wrote: ↑ Ten years isn't even that old. Synthetic oil has it's benefits (more protection, better low temp performance, high heat performance), its more expensive but you can run longer oil change intervals (10-15k+). Just make sure your car doesn't burn/consume oil; you won't be able to take advantage of the long oci and might as well stick with conventional.
Never blindly double your oil change interval because you are using synthetic. There are many factors in how quickly an engine can degrade motor oil. Things like small sump capacity or use of forced induction (especially turbocharged engines) can degrade motor oil much faster. If you plan on keeping your vehicle long term, do an oil analysis to properly determine how long you can run an oil before the additive pack of the oil deteriorates too far.