That's pretty much the analogy I used to then 9yo DS driving home from him being diagnosed; I wasn't expecting such a definitive diagnosis to be made so "easily" and I was reeling at the time, but he needed to know what the appointment was about and what it meant.
DH has an automatic. I drive a manual which I'm well used to. I've driven the same make for 10+ years because it fits my ergonomics. When I get into DH's car, I'm still driving and doing all the observing and reacting required for driving, but the controls aren't in the same place. I've got a dialogue chuntering through my head of "don't use my left side" and my left hand flaps for non-existant gears when I change speed, the controls feel odd and clunky, my right quad burns because of the awkward angle of the accelerator etc. I'm still driving but there's more mental effort and I get physically tired much quicker.
That's what it must be like for DS getting through most days, manually vetting most interactions, battling sensory input.
Another analogy is like every day being like an all-day job interview. Every one puts on their best, polished front for an interview and it can be done for short phases, but to do it all the time, you'd lose your sense of self, you'd be exhausted when you get in, you'd begin to dread the day ahead when you get up each morning.
And if you're masking with autism, it's not just manually filtering your way through unwritten laws of social communucation, you're probably also battling physical urges to stim, to hide away, manage body language, and brain-mashing sensory input like that clock on the wall that ticks out of synch with your heart beat, or the faint hum that no one else seems to hear, or the way that someone's nostrils whistle when they breathe.
It was DS's regular explosions the moment of stepping out of the school doors when he could let the mask drop, once cuminating in a 4 hour meltdown that lead us to investigate/ diagnose. He is exemplary at school, but at great personal cost. He can't do anything other than zone out for at least two hours after school. Now at secondary, I judge from his head position as he walks up the road to the car if it's a radio off, and wait in silence until he can talk day.
We all have a best, polished front, but with autism it's having to be in that mode pretty much constantly to socially survive. You may not know that your doing it, but the extent of it impairs your ability to function in wider life. We hear a lot about meltdown, but shut down is another significant trait where you just can't process anything else.