Can any fluid replace the mercury in a manometer?

Yup, any liquid can be used. The reason why mercury used is because it has high density. Hence for same pressure difference, we need small column height compared to other liquids. As. P = density*g*height. read more

In fact if you want to measure very small pressure variation with high accuracy, you should use a less denser fluid as it will give longer column deviation. So basically, As far as you are using density value of the liquid used , any liquid will work in a manometer . Enjoy. read more

Yeah, ATF is nowhere near as dense as mercury, hence the sucking and losing of fluid on your part- you would need a very tall manometer to keep the ATF fluid in. On the homemade manometers people talk of using small ID aquarium tubing, something that really throttles the air flow down. read more

Generally in U-tube manometer we are using mercury as manometer fluid whose specific gravity is 13.6. Which means it is 13.6 times heavier than water. if we take specific gravity of oil as 0.9, nmercury is 15.11 times heavier. read more