There are vegetable oils and mineral oils. Some vegetable oils have double bonds(called drying oils - linseed is one and with added catalysts(dryers) makes the

There are vegetable oils and mineral oils. Some vegetable oils have double bonds(called drying oils - linseed is one and with added catalysts(dryers) makes the furniture varnish we know) drying oils in roads - the drying aspect hardens the road, like slow-slow cured cement - at the cost of brittleness = a tradeoff. So the correct formula of mineral oil/vegetable oil/drying oil = max endurance. vegetable oil = 5-10x the $$ of mineral oils mixes(asphalts). Asphalt is the solid residue of oil fractionation is decanted into 45 gallon drums for trade(but is also bulk shipped in heated tanks , or = tank shaped lump. MacAdam created macadamised roads = a graded mixture of crushed rock from dust to ~.5 inch with the calculated minimum void space. Void space uses up asphalt, so minimum voids. Minimum voids + asphalt = strongest tarmac = well studied. Hot roads = higher melt asphalt needed - or sticky roads.