What makes an old vehicle a POS? Age? Yours will get old. Miles? Yours will accumulate them as well. Things breaking? Yours will have a lot more things to break and inspection criteria to meet being OBD2.
You could have bought an older truck, for ~5000$, and with the money saved you would have enough to buy, I’m approximating here, but 3 YEARS worth of gas, AND money set aside for repairs that could possibly occur.
I’m sorry I just don’t agree with somebody buying a newer gas hog vehicle just to complain about gas prices, it’s ridiculous.
YOU set yourself up by trying up easy money into the truck that gets bad MPG, there is no way around that, it was your decision not looking into the future and not expecting gas to go up is an oversight mistake.