Where should the needle be when the temperature guage is operating correctly (and the car not overheating?)

I've got a 280 SE 4.5, and normally on the highway temperature is just slightly higher than dead centre of 175. Today in moderate traffic (not even stop and go) after highway driving (which had normal temperature) the guage rose to just above 175 (most of the numbers 175 were showing below the needle). Is this OK?

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Jason

1972 Mercedes 280 SE 4.5
Green on Tan
"The Diplomat"

This sounds normal.

175° or slightly above (but not to the 212° mark) is normal. It should be 175° on a highway without issues even at 90+ for hours. If it gets higher than that I'd suspect a thermostat issue.

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Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

Thanks a lot!

So it is OK that the temperature rises a bit. Good, makes me feel better to know.

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Jason

1972 Mercedes 280 SE 4.5
Green on Tan
"The Diplomat"

I've found that even after driving on the highway, with the A/C on, the coming off the highway, the highest it gets is just above the 175. That is to say, the needle points such that most of the needle (but not all) is above or at the top of the numbers 175. After sometime, the needle comes down to closer to an absolute register on 175.

My thoughts are that on a vehicle this age, it is an accurate thermostat and thermometer that are producing the increased register on the guage, combined with an older car's inability to regulate the heat as well as the newer cars.

Thoughts?

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Jason

1972 Mercedes 280 SE 4.5
Green on Tan
"The Diplomat"

There is a "rule-of-thumb" used by Mercedes in their design philosophy for these cars as it relates to your perception of the critical information displayed on the instruments. The most critical data when the engine is operating is the status of the oil pressure and the operating temperature. For these two pieces of data: For oil pressure the needle is "pegged" at the top of the gauge at road speed and above zero, usually at or somewhat below midpoint when idling; the needle should peg virtually immediately when you move above idle and get to about 1,500 rpm. The weight of your oil will affect this as well. For the temperature gauge, the normal for the gauge needle is approximately horizontal. It will be higher when you use AC but is only a worry when you are always in the red zone.

This is their approach so that you as a driver can determine at a quick glance the status of these critical items without the need to read and interpret a specific number on the gauge.

Remember, there is always some degree of variation in the way gauges register and sensors operate which accounts for the small differences in the way a gauge in one car may vary from another car.

Hope this helps...

Thanks!!

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Jason

1972 Mercedes 280 SE 4.5
Green on Tan
"The Diplomat"

It's also worth noting that the temperature gauge is an actual thermometer with a direct, gas-coupled link to the engine. It is showing, accurately and in real time, what is happening in the engine. The display in a modern car is interpolated to pretty much always be in the middle and doesn't really show you what is going on with the engine, precisely to keep people from having questions like this. In a modern car, you won't know about a potential overheating problem until after it is too late, the needle pegs and there is steam coming out!

It's harder to get rid of the heat in stop/go traffic than highway.

I agree that it sounds normal, and with the last reply in that the older cars were better in relaying information than modern cars. I like watching the needle go up and down, especially on oil pressure...on modern cars they usually come on when the damage has already begun.

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