Unpopular ATS opinion (?): I like California's 55mph speed limit
It's very chill and relaxing to drive, which is one of the best things about playing ATS in the first place.
You don't have to bother with changing speed limits for country and town interstate sections at all; just steady on 55.
I suppose you never do elsewhere either: if it changes from 65 to 70, nobody is forced to speed up but my brain makes me feel like I should.
It's very economical on fuel which I find very satisfying and it's suitable for pretty much all weather conditions. Sure it's slower to complete deliveries which costs money but I find it lets me look around and enjoy the scenery more as well. And you essentially get it back on fuel savings anyway.
I just make sure to fill up on gas just before entering and just after exiting the state though, lol. Paying $3.77 rather than $5.28 per gallon is a lot better, especially running the real economy mod where every dollar counts in your expenses.