Sorry for this but I need help with my 1992 K3500

Oups! Seems like I forgot some really basic stuff!

Regarding the ODO I actually checked it by driving a stretch of road I know and the mileage counter seems to be quite accurate

It's a 350TBI that's bone stock.
4L80E transmission that seems to be in quite good condition.

The mileage has been horrible since I got it.

Normal road tires on stock rims

Engine temp according to the gauge at least seems OK

Quite a soft foot actually, no racing machine anyways ;)

Can't tell the RPM since theres no RPM gauge...

240.000 kilometers on the ODO