Help with pricing for hauling with a pickup

Just bought a pickup truck. I’m only using the bed 10% of the time so I’m gonna try and offer some hauling services during my free time.

What would you recommend I should ask as payment? I was thinking round trip mileage based plus a flat fee. So gas is about $4 a gallon around here right now so if I’m getting 17mpg I need to charge at least 24¢ a mile to break even on gas. So say someone wants me to take a load to the dump that’s 20 miles from the place I’d pick up and I end up charging 40¢ a mile plus like a $30 fee totaling to $46.

Do you think that’d be under/over priced? Is there a better way to go about it? I’m assuming the people willing to pay for a service like this are just avoiding renting a U-Haul truck so I would think I’d have to make it comparable to that plus the price of the convince of not having to go through all of that yourself.