If oil is going to be used in the fight against fat, the best choice would almost certainly be olive oil. Olive oil is rich in monounsaturated fat (MUFA), the mainstay of the famous Mediterranean diet. Numerous large, long-term studies have demonstrated a powerful association between relatively high dietary intake of MUFAs, and reduced risk of abdominal obesity, diabetes and heart disease.
Perhaps the final word on this topic is that while some kinds of abdominal fat can be particularly dangerous, there tends to be a silver lining. Abdominal fat tends to mobilize first when a meaningful weight-loss effort is made. In other words, the best and most reliable way to reduce harmful belly fat is simply to eat well and exercise.
If I were using oil to grease the skids for losing belly fat, my top picks would be omega-3 oils from fish, krill, seafood, algae, flaxseeds and/or walnuts, olive oil and canola oil, which is a source of both MUFAs and omega-3s.
But I would place an even greater emphasis on a different kind of oil altogether: elbow grease!