I've been hunting out of my Superduty diesel. I've been really surprised how little it bothers the pigs and deer. I go slow using parking lights for illumination if it really dark and stop every now and then and scan with thermal. It's shocking to me how many times I've seen pigs or deer 100yds or less yds away when I stop and look. If i'm about to crest a hill in a good area, I park. and walk to the top. I will often find pigs and or deer 50-75 yds away from where the truck is parked still idling.
It is a less than ideal setup for sure, but it makes me think super quiet motor may be overrated, at least where I hunt. I'm not sure that you can truly drive quietly enough for them not to hear you at all. The tires on the road or grass still makes a good bit of noise. Sneaky unusual sounds seen to scare them worse than blatant familiar one.