Review on 🚗 ESUPPORT Car Motor Vehicle Black Face 2" 52mm Pointer Vacuum Gauge Meter with LED Light: Efficient Performance Measurement Tool by Chad Moser

I use one of these to maximize the mileage of my van. The longer you hold the needle in a 15-30 inch vacuum, the better your mileage. I can get 2mpg by using this to balance the speed/tachometer/gauge readings. Sits on the dashboard in a case that I also got from Revain. This sensor is a little sticky in its movement though, so it's not super accurate, but you get a really good idea of what's going on. An added benefit is that these sensors are a good diagnostic tool for things like burned valves, timing issues and general engine health. There is a lot of information on the internet about this.