It was a tractor that would throw engine codes because the tractor with its 160 degree thermostat would never reach operating temp. After around a year of the tractor OEM and the dealer trying different things to fix the issue, they basically told the guy we can't fix it. so the guy changed from the factory 160 to a 180 degree thermostat and that repaired the issue. The mistake the guy made was telling the OEM what the fix was. His reward was lose of warranty.Question here is who changed the thermostat. If the dealer did on the advice from Ford then they should not have voided the warranty. If the owner changed without authorization then they could nit pick and do it just to be jerks. OF course they are more worried about the EPA fining them instead making the necessary change and getting it re-approved by the EPA. Government bureaucrat policies are sometimes plain stupid. Sometimes the local mechanic has a better idea what is causing the problem than the factory as he dealing with real life problems.
It like my 73 IH PU that the factory 180 degree was too cold and I had water condensation in the crankcase. I went to an 195 degree which resolved the issue. IH later changed the thermostat spec for my 345 engine.
Of course now days the states stick a sniffer up the vehicle butt to see they are meeting the factory preset specs and then demand you make the vehicle operate worst just because someone miss entered factory information.