Bellal981

I have e200 2004.. I got problem with oil coolant.. mechanic remove it.. then I clean radiator. And change thermostat 87. Now tempreture go from 85-100. After start in 10 minutes Degree go to 100 then go down to 85 then rise again to 100 ( stay moving ). It's not stable degree keep like rise and go down in all way inside city and in highway 110 km/h.
is this normal??

e350forme

keep draining/repalcing coolant
or thermostat defective