Your experimental result would probably be greater than the accepted value for the specific heat capacity.
In this type of experiment you would apply a known amount of heat to a calorimeter containing a known mass of oil and measure its temperature change.
Let's say you add 1000 J of heat but due to heat loss (inevitable, proper insulation or not) only 900 J of that are transferred to the oil. You don't know this number because it is difficult to quantify heat loss.
You are still measuring the temperature change but instead of accrediting it to 900 J of heat, the calculation uses the 1000 J value. This means it looks like it takes more heat than it actually does to raise the oil temperature one degree. This leads to the higher SHC value.