I while back someone posted the stl file for printing a fuel return block. I’m unable to find the post so going of memory I don’t remember him talking about which filament should be used, but I could be wrong.
Unless you specify the correct filament it will most likely be printed with PLS. It will start to soften at 120 degrees.
I use Carbon Fiber PETG-CF. It is a high-performance engineering thermoplastic, and fortified with carbon fiber, this filament is an engineered Metal-Like Strength to excel in high-stress applications, offering superior toughness, chemical resistance, and thermal stability. It performs well in continuous service temperatures up to 392–428°F and resists exposure to fuels, oils, and industrial chemicals. This combination makes it ideal for automotive and high-temperature functional parts. Carbon fiber reinforcement also reduces warping and improves surface flatness, making printed parts more reliable and precise for functional applications.
I had a couple print up with PETG-CF and selling them for $50.00 including USPS shipping. Contact me though the forum or email at jeff@fisherresource solutions.com
