I'd go through and get a full tune up done. Spark plugs, oil, oil filter, air filter, run a couple tanks of premium gas through it. It wont hurt it and will absorb some of the gunk in your engine. Being that you are calculating less than half what it should be i'd probably check how your measuring it.
The old people seem to be worse than the teens texting, I say once your 60: driving test every year.