This is idle. 06 f350. Gaskets and egr bulletproofed prior to buying. I can never get an answer on what is too high. What are the normal ranges? I know you want to stay between 10 but what is normal.

iirc the stock 6.0 is a 190 or 195 thermostat.

I would start watching close at 210, get nervous at 220, and tear it apart at 225.

Oil temps on the 6.0's run hot. Always have unless the truck had a bigger oil cooler put in when work was done but most people do not due to the enjoyment of putting them in. Not quite as bad as studs but pretty fucking close.

Fuel gage dropped to empty on me. Got a "fuel level data error" on dash.

Sending unit?

Yes, known issue. I know they have a TSB out that updates the PCM to not illuminate the CEL when error comes up but does not fix anything. Just replace the sending unit.