Tarmac issues

What you are experiencing is a common phenomenon called asphalt bleeding (or flushing). The Cause: Tarmac is bound together by a petroleum-based product called bitumen. When the sun beats down during hot weather, dark tarmac absorbs a massive amount of heat. Combined with the stationary weight of parked cars, the bitumen softens and gets squeezed or drawn up through the tiny air pockets to the surface. It leaves a shiny, sticky, dark, or oil-like patch right where car tyres sit. The installers are right that heat and vehicle weight are the triggers. However, excessive bleeding can also indicate a slightly rich mix (too much binder used relative to stone) when it was laid.