I flushed the cooling system and added a 50/50 mixture of glycol and distilled water to my 89 Eldorado. It has the 4.5 litre and 104xxx miles.

The current thermostat isa 195 degree model. When purchasing the new stat I was offered 3 choices 160, 180 and 195 degrees.

This leads me to ask the question, on a car with more than 100,000 miles should one consider lowering the range or stick with the service manuals recomendation of 195?

I think 160 is too low but I am considering the 180 thermostat.Would 15 degreesmatter all that much, since even the pricey themostats tend to not open exactly at the range specified, or is it that critical to run closer to the 195 degree mark specified?

Thanks is advance for yourassistance.

 

Best to run 195. 160 will dissable tcc, egr and keep engine in warm up mode.... meaning terrible fuel economy.

 

Thanks Slowroll for the quick response.

I have owned other GM products, but this is my first Cadillac.I don't have have to tell anyone what a great car it is, I can't believe I waited this long to own one.

But if you kind folks will permit me, maybe you or other members can help me on a couple of followup questions.

1. What do you say to guy at the parts store that insists on the 180 degree thermostat because of the amount of mileage on the car?

2. What is the "normal" range for the 4.5 liter? Once warmed up mycar ranges between 197 and 218, but I have seen it as high as 222 for a short time. A typical example would be after exiting the freeway and then waiting in traffic or a stop light shortly after exiting, the stat opens andthe tempature returns to somewhere around 200 degrees. Is this normal and at what point should I be concerned; at 230, 240?

Thanks again for the all the help from members to this newbie with many questions.

What a great site!

 

I have two Northstars, my old one having a digital gauge, and in town it gets to 220, on the highway 200-205. I've seen written here that extended periods over 235 would be a cause for worry, but I'm no expert.