IMHO it's not coolant, but if you're concerned have a used oil analysis done to check for it. I use
Blackstone Labs; for around $30 they'll analyze your oil and let you know how your engine is doing.
A small oil leak could be in a hose, power steering, or just some that the jiff lube place spilled. If the vehicle were mine I would wipe it off and check it every day or two to see where it's coming from.
Cost of synthetic:
I get about 1.2 mpg better in my Grand Cherokee using synthetic oil. Doesn't seem like much, but over 5000 miles it saves more than double the increase in price of oil. some vehicles don't get an increase in mpg, and if yours doesn't you'll have to decide if the extra cost is worth it.