Running to cool?

[Downey]

So I think my truck is running a little cool. Normally cruising down the highway 70mph ect is 168-175 and eot is 8-11 degs warmer. But when hook the 32ft 13k fifth wheel it runs around 205 ect and with in 2-3 dog for eot.

Is this to cool for empty? Some times the best suffers too. Then at times it runs up at 195 the. Once starts cruising again drops back right back down.

 

[Cutting-Edge Diesel]

replace the thermostat