Porter-Cable via eBay offers its Porter Cable 4-Gallon Stack Tank Air Compressor, model no. PCFP02040, for $119.99 with free shipping. That's the lowest total price we could find by $78. It features a 1.1HP induction motor with a cold start valve, oil-lubricated pump delivering 3.4 SCFM at 90 PSI, and 135 PSI max working pressure.