The correct oil/fuel mix will not effect how the saw runs in the short term, so don't expect to simply replace the tank of fuel with a correctly diluted sample and the moment you start it up it will miraculously cure itself. The oil is only a lubricant. It only effects the running in terms of lubrication to the moving engine components- too much oil will produce excessive exhaust fumes, choke up the exhaust eventually and will over oil the spark plug causing starting problems. Too little oil in the mix will eventually lead to metal to metal contact within the engine and the engine and will cause expensive/near terminal damage.
Richards answer is correct. The easiest way to determine what type of oil you have is to read the bottle of the oil you are using and the recommended ratio will be clearly marked. If its one of these cheap supermarket brands and no ratio is listed or it states multiple ratios, then bin it and buy some decent, quality oil from a machinery specialist.