Slipstream / Tow
VerifiedSitting in the wake of the car ahead cuts drag on a straight, giving a following car a speed boost.
A car pushes through the air and leaves a pocket of low-pressure, slower-moving air behind it. A car following closely on a straight can sit in that pocket, meeting less resistance and gaining extra speed for the same amount of power. That's the 'slipstream' or 'tow'.
It's the helpful side of running close behind another car. The same wake that costs a following car downforce and grip through the corners, dirty air, works in its favour once the road straightens out.
A strong tow can be worth several tenths on a long straight, enough to close a gap or set up a move at the braking zone, which is why drivers jostle for a run out of the last corner before it.