If it's spec'd for a 5w30, I would run a cheap but good syn blend (e.g. Chevron Supreme, Mobil Super) and keep it topped up.
The story goes... conventional does not burn as much as synthetic because conventional does not flow as good as synthetic. Personally I never believed this to be true, but also I haven't owned an oil burner since 2009. In your situation, it could not hurt to try.
The story goes... conventional does not burn as much as synthetic because conventional does not flow as good as synthetic. Personally I never believed this to be true, but also I haven't owned an oil burner since 2009. In your situation, it could not hurt to try.