One of the things that perplexes me is that the autobots didn't really adopt car culture very much, or maybe I am missing some things. For example, did an Autobot ever have personalized mudflaps? Dice on the mirror or raccoon tail on the antenna? Truck nuts?
Many of the vehicles the Transformers turned into were highly customized. The most obvious example was Optimus Prime himself turning into a Western Star 5700.
Here is how the truck comes "stock":
And here is how Optimus customized it:
As you can see smoke stacks, front bumper, clearance lights, mirrors, and fuel tanks are all very customized - not just painted.
I'm fairly confident custom mud flaps would not have been a problem, and I can't say for sure is he didn't actually have them.
Of course the most famous of our Transformers, Bumblebee, was certainly not a generic 2016 Camaro (pictured below):
Bumblebee from Transformers 5: The Last Knight enjoyed really spicing up his image with completely customized ground effects, a spoiler, and hood scoops.
Hot Rod(Rodimus) exemplifies a lot of car culture both in physical design and the character's personality.
As for personality, the specs on the back of his original toy box describe him as an all-American-boy, typical adolescent, who doesn't follow rules too closely. He's impulsive and can be hotheaded. A toy commercial featured him taunting his enemies and saying, "watch my smoke!" He is often described as a rash and arrogant, turbo-revving young punk.
Beyond Hot Rod, there are numerous other Transformers with modifications and embellishments beyond a stock vehicle. From the original cartoon, Wheeljack and Jazz are both modified for racing and feature racing paint jobs as well. Sunstreaker is a customized Lamborghini Countach with supercharger intakes. The Hot Rod Patrol was a collection of four Micromasters who turned into cars with superchargers and custom flame paint jobs. Side Burn from Robots in Disguise also featured a custom flames paint job and an exposed engine.
Regarding mudflaps in particular, according to TF Wiki:
In the The War Within #4, Elita One's silhouette is depicted on Optimus Prime's mudflap in vehicle mode, similar to the "Trucker Lady" silhouette decal seen on modern vehicles. Optimus Prime also has a bobble-head of her inside his cab.