When I fill up my almost-empty car (20 year old, diesel engine), if I pump 50€ worth of gas, the needle goes up to 55 or 60%, tops. But to get a full tank, I only need to pump another 15€.
Why is it so non-linear? Is it just old and out of whack? Is there a design choice in there? What am I not getting?
If I recall right it’s some weirdness with how the float bulb in gas tanks, which is used for that display, works.
I don’t think I’ve ever seen an instance as extreme as what you’re describing myself, but there tends to be more actual fuel volume at the lowest and highest ends, so the gauge isn’t exactly linear. Not sure if it’s something that can be compensated for by the manufacturer in the design or not.
IIRC, the guage running from “very nearly empty” to “almost full” is an intentional thing, weirdly enough.
On the upper end, it’s because supposedly people feel better if they fill the tank and the needle doesn’t start going down immediately.
On the lower end, it’s to give people an earlier warning that their tank is (very nearly) empty, so they don’t run out of gas on the road.