Why do you think we’re refining methane-burning engines?
You are going to need to produce 10,000x more energy than your fuel contains to make the fuel, and that energy has to come from somewhere.
Are you even attempting to Google these questions before posting them here with such an aggressive tone? Manufacturing oxygen on Mars is demonstrated engineering [1]. Manufacturing methane, theoretically sound and demonstrated in the lab [2].
This is what I meant by the aggressive strain of ignorance having overtaken the science with popular astronautics [3]. Some folks read a hot take on Musk and what Hawthorne hasn't done, ignore the thousands of scientists demonstrating actual technology a hundred million miles away, and then assume they're vindicated when the rest of us get tired of arguing with willful denseness.
[1] https://www.science.org/doi/full/10.1126/sciadv.abp8636
[2] https://ntrs.nasa.gov/api/citations/20170001421/downloads/20...
I just don't see a Mars colony as a reasonable goal without sending potentially thousands of rockets full of tools and materials, which is too expensive to do without an already existent space mining and processing industry.
The only reasonable method of shipping rocket fuel to Mars or anywhere else in the solar system is to mine and refine it off the moon or an asteroid, which means a moon base or mostly self-sustained asteroid colony would need to exist first.