[bbnks2]

Spoilers do not generally add drag. They create a pocket of high pressure which allows air flowing over the roof to pass over the rear of the car more easily. This generally reduces drag and rear end lift. A wing uses that airflow to generate down-force which is where added drag can become significant.

Dragy is a decent app but you're talking about comparing different conditions, different dates, different mods, different roads, different slopes, etc. Way too many variables. Spoiler surely isn't one of them though LOL.