To me it seems, you both are rather debating semantics.
Of course it is "speculating" trying to estimate fuel prices, but this is not meant, when people condemn "gambling" on the stock market. What they mean is people with lots money investing wherever short term profits are possible and often gaming the market while doing so. So creating unexpected price changes for the actual industries needing those supplies and they obviously don't like that. But I couldn't draw a clear line between "necessary gambling" and "unnecessary gambling".
Of course it is "speculating" trying to estimate fuel prices, but this is not meant, when people condemn "gambling" on the stock market. What they mean is people with lots money investing wherever short term profits are possible and often gaming the market while doing so. So creating unexpected price changes for the actual industries needing those supplies and they obviously don't like that. But I couldn't draw a clear line between "necessary gambling" and "unnecessary gambling".