Attached is his old logo concept (on the tshirt comp that says Paramount). He likes the font type and font color. This doesn't mean you can't play with it and offer up your own solution - but should give you an idea what he likes.
He also likes the two trucks showing in the back facing outward from one another. He does NOT like the abstract figure displayed on the front of the logo which was something we played with, but was too abstract for him and in retrospect don't know what we were thinking.
Use it for inspiration or do your own take on that.
The green color is inspired from his personal truck which is actually that monster green color (I've attached a picture of his truck for reference). His truck is sorta like part of his brand. It's this huge looking, you can't miss on the street kinda truck. Everywhere he goes, they know he's the diesel mechanic because of the truck (this is back when he was a "mobile" tech). He also likes black - think Harley Davidson bikes.
He's kinda rednecky, likes and owns Harley Davidson bikes, boots and leather jackets. You get the deal. This is what he wants his brand to reflect - something cool and grungy.
I've also attached an Antique Archaeology t-shirt that he really likes, so it gives you insight to his likes. I took notice of the font type and design style - again kinda grungy. Just use for inspiration, no need to do exactly what is said here.
This whole design style is actually quite prevalent in the trucking industry. In fact Peterbilt trucks make tshirts that he loves. Just google Peterbilt tshirts.