on my mom's campro0 gen2 hi-line, auto-cruise "on" really save fuel.
on highways of +-300km stretch, i seldom drive without auto-cruise, within speed limit of course.

i agree with u.
may be the ecu is in learning process?

from my observation,

1. auto-cruise set at 120km/h more or less have the same rpm without, provided the road is level.
it may fluctuate a lil bit if there is gradient, coz auto-cruise tries to maintain speed.

2. auto-cruise cannot be set at low speed (<50km/h if i'm not mistaken).

but that on my mom's campro0 gen2 la..not yet tested on my mom-in-law's exora bold cfe..

hahahaha

very easy.
1. switch it on,
2. speed up car to ur liking,
3. then "Coast/Set" it.

auto-cruise can be cancelled by:
1. braking,
2. or "cancel" switch.

re-apply auto-cruise after cancellation by:
1. switch "Accel/Res".

it's quite convenient to push "Accel/Res" to gain speed, without pushing ur accelerator

no la..if u travel jauh2 mmg penat kalau kaki kanan xangkat.
try it. Sg. Besi-Ayer Hitam @120km/h FC 7.0L/100km. campro0.

(but hey, i cannot drive all the way @120km/h..if u know what i mean)

lupakan je la. aku ulang alik NPE-Jln Ampang ni naik kapchai jek..

what's the problem with the electrical system eh?

my mom's gen2 twice a year the headlamps went kaputt,
but my wifey myvi hl perfect for 4years?