2-1/2" Oil Filled Vacuum Pressure Gauge, Water Oil Gas - Stainless Steel Case, Brass, 1/4" NPT, Lower Mount Connection -30HG/30PSI

TOOL MAKES JOB OF SETTING TDC VERY EZ... VERY ACCURATE READING... JUST PLACE TOOL IN NUMBER 1 SPARK PLUG HOLE... (USE RATCHET WITH 16 MM SOCKET) ROTATE ENGINE CLOCKWISE.. AS U DO SO GAUGE WILL FLICKER VERY SLIGHTLY TO POSITIVE VACUUM THROUGHOUT ROTATION ( NEEDLE JUMPS TO RIGHT VERY SLIGHTLY ) ... (INDICATING COMPRESSION STROKE) CONTINUE ROTATING ENGINE.. UNTIL NEEDLE SUDDENLY DEFLECTS TO THE LEFT INTO NEGATIVE VACUUM ..WHICH INDICATES EXHAUST STROKE... STOP AS SOON AS GAUGE INDICATES NEGATIVE VACUUM AND THEN U START TO TURN ENGINE VERY SLOWLY COUNTER CLOCKWISE .. NEEDLE WILL SETTLE INTO THE ZERO RANGE = TDC ... THIS IS YOUR TOP DEAD CENTER... GAUGE WORKS GREAT !!!

I purchased 2 of these so I could compute Total Dynamic Head (TDH) for my new Pentair intelliflo 3 HP pump that I installed this morning. These gauges worked perfectly and appear very accurate. When I re-plumb my pool system, I plan to add a couple flow meters downstream of the pump but, in the meantime, these gauges, allowed me to estimate water flow rate (GPM) based on TDH calculation, pump RPM, and pump curves. Until recently, I had no idea what the suction was and had to rely on old filter pressure gauge. These are top notch quality and seem very accurate and have come in very handy!

Normal don't leave reviews cause everyone else has done it, but I was just too impressed with this little guy. Showed up to the house in good order. It was reading a few inches under 0, but I wasn't too worried about accuracy for my purpose. When I went to install the gauge, I noticed a fantastic feature on this product. It comes with a little plug on top that zeros out the pressure. That's pretty neat.

Nice vacuum gage. One problem is vent on top of the gage in that instructions say to pull up the rubber stopper on top to vent air off but when doing so the stopper comes off easily and oil now all over the gage.

Using this as a fuel pressure gauge on a Cummins diesel engine. Just installed it the other day so can't speak to it's longevity yet, but it was shipped quickly, was exactly as described, and worked. Looks great, is easy to read, and when checked with a known accurate gauge was very close to showing the same pressure as the known gauge.