I just received my Viair 400P-Automatic Portable Compressor as a replacement of my old 400P. Get the item here.

The difference between this and my old buddy is that this automatic compressor will shut itself off without you flipping the switch. In the past when I used 400P non-auto version, while filling up each tire, I had to run back and forth between the compressor and the tire to get an accurate pressure reading. But with the Automatic, I can stay at one tire, make sure I’ve got the ideal pressure, then move on to the rest without touching the compressor in between.

Here are some side-by-side comparison photos:

Left: 400P  |  Right: 400P-Auto