Some info that I found that maybe useful to others.
We receive many questions regarding gauges. Particulary, consumers want to know which is better for their car, mechanical or electrical gauges. Both mechanical and electrical gauges are equally accurate. The determining factors more involve installation and application than gauge accuracy. This short list of advantages should help you make the best decision for your specific application.
MECHANICAL GAUGES Mechanical gauges do not require 12V power to operate. They make direct physical contact with the item they are reading. They do this through tubing or lines, which eliminates the need for electrical signals.
Ideal for vehicles that operate on voltage other than 12V, with no voltage at all, or operate on a battery with no generator.
ELECTRICAL GAUGES Full 270�° sweep, makes them easier to read accurately.
No large connectors and tubing coming out the back.
Can be mounted in more unusual positions without connections showing
Easier to install in tight areas.
Easier to install a great distance from the item being measured.
Stops fluids from entering the passenger compartment.