Mike,
From my "for what it's worth" department
Had two liquid filled gauges in my car. Both failed to read accurately after a month or so of use. When new, they would read 6 to 7 pounds, but when they failed they would indicate anything from zero to something short of 7 pounds.
Upgraded to an AutoMeter #2172 and have not had another problem in over two years.
Standard disclaimer..... your mileage may vary
- Jim -