I've got an Autometer (yeah yeah) mechanical fuel pressure gauge installed in my dash connected to a high pressure isloator under the hood. What is the best fluid to use between the gauge and isolator? I'm using antifreeze as the instructions said, and every time it gets hot outside, the needle will read some insane level and not give me proper readings. I'm guessing this is due to the antifreeze expanding. Anyone able to help me out with this problem?