W-20 synthetic oil is all the rage these days, but what engines actually need this grade of motor oil - and, more importantly, how long does it last?

Like all Mobil 1 Extended Performance motor oils, Mobil 1 Extended Performance 0W-20 provides outstanding ... including simulated highway, city and road trip driving, changing the oil every ...

Pennzoil specifically warns against using different oil weights — the number following the dash — in your car's engine. It's acceptable to use 0W-20 engine oil in place of 5W-20 or even 10W-20 ...