Swedish car mag runs various long term tests, sometimes for 5 years.
They have compared 5 years and 200,000km with a diesel V90, to a petrol Volvo 850GLT that they also ran for the same time/mileage 30 years ago. They included all costs - fuel, insurance, taxes, repairs, tyres, and depreciation.
Adjusted for inflation, the old 850 was just a couple of hundred quid cheaper than the V90. Total costs for each car (adjusted) was around 50,000SEK, or £42000.