Temp rise after fuel treatment

[FutureSelf]

I put 5oz of lucas high mileage into my 2010 gmc yukon after about 3 miles the temp went above normal operating temp to around 230 240 and drops fast when i stop at light or park. Used it cause i thought acceleration felt a little late to respond. Been running fine before i went down the auto section at Walmart and then put in 15 gallons of gas 10 mins later its at 230 fans are on no leaks no hissing new temp sensor few months back coolant full and recent just bought a year ago. Not mechanically inclined in detail but can recognize some symptoms. Never checked my thermostat could this be what it is? Any advice is helpful and again im not a pro so please use laymans terms lol thanks

 

[02Lightning]

My guess is the fuel treatment is not related.

 

[Geotrash]

+1 ^^^

The timing is coincidence. Lucas increases oil viscosity and is useful for keeping aftermarket cams happy, or for increasing oil pressure in an engine with significantly worn cam journals and bearings. It won't on its own, increase engine temperatures. My guess is you either have a blockage in your cooling system (e.g. radiator), a water pump with a loose impeller, or something else going on.

 

[gpracer1]

Sounds like a water flow issue, thermostat or clogged rad........assuming it is full.

 

[Foggy]

Not related.... find the cause of your overheat situation.. Check
coolant level... Check Fans for operation: they have 3 settings and are
always simultaneous. Off/ Low Speed/ High Speed. You can run the AC and
that should kick them on at Low Speed pretty quickly...

Others have suggested the Thermostat could be bad.. Or maybe even the
coolant temp sensor has gone bad...