Aeromotive has long been a proponent of "dry" fuel pressure gauges. In fact, this type of gauge is all we have ever offered. Many of the gauges on the market today with the exception of ours, were liquid filled. While there are many advantages to the liquid filled design, there has always been on inherent issue; when the temperature underhood increases, so does the oil inside the gauge. This causes the pressure inside the gauge to read differently as the oil heats up and expands. Now instead of reading fuel pressure against atmospheric pressure, it reads against the pressure inside the gauge case itself. This leads to false readings and in many cases a wild goose chase for the user since the pressure will change with temperature. If you would like to learn more about this issue and the causes, you can read more about it in our FAQ section here: FAQ On the flip side of this discussion, the oil inside the gauge does help with vibration and the durability of the gauge. Aeromotive has long weighed the durability of the gauge against the problematic pressure changes. However, all that is about to change. Aeromotive has teamed up with Auto Meter, the industry leader in high-performance gauges, to design a fuel pressure gauge that "IS" liquid filled, but offers a solution for the pressure fluctuation due to temperature changes. These all new gauges offer a pressure relief valve that equalizes pressure between the atmosphere and the gauge when activated. Before taking an accurate reading, simply pull the pin to equalize pressure in the case of the gauge. Now it will read fuel pressure against atmospheric pressure, no matter the temperature. Aeromotive offers these as both high pressure (EFI) and low pressure (carbureted) gauges. For more information, see the part numbers listed below. 15632 - 0-15 PSI Fuel Pressure Gauge 15633 - 0-100 PSI Fuel Pressure Gauge