THe engine oil temp display in the DIC reads approx. 13 degrees lower than the water temp. i.e. in the garage, when the ambient temp is about 56-58, water displays at 56 degrees. The oil temp displays at 43 degrees.
I thought the sender might be bad, so I replaced it - identical low reading.

What does everyone else see?
Where might the problem be - just inaccurate?

I guess the major concern, is the difference at track temps. If it's consistently 13 degrees low, then I can deal with it, but there isn't any way to tell withouit installing an aftermarket gauge.

Suggestions???

Thanks,
Joel

 

ttt

 

Mine does read lower too, I don't have a specific number but I always thought it was normal.

 

Usually the oil temp will read less than the water temp under normal operating conditions. The water cools the oil so as long as you are not developing a lot of power the oil will not get too hot. However, once you start doing a lot of WOT runs and generating a lot of power (heat) to run the car around the track the oil gets hotter than the coolant.

Bill

 

Bill,
You missed the point of my question. If I could be sure it was always the same 13 degrees off - through the entire range - that would be fine. My concern, is that I don't know. Suppose it's 70 degrees low when it reads 250?
The 13 degree low reading was ambient temp in the garage, without having run the engine.
Possibly the only way to know for sure, is to install a second gauge.

Joel

 

db2xprt,

The oil temp sensor is way down low by the oil filter. The coolant sensor is higher in the head and engine compartment. Possibly you're seeing the temperature difference because the oil sensor is closer to what is probably a cold floor, while the coolant sensor is higher (warmer air) and is more protected from drafts in the more insulated part of the engine compartment.

When I'm cruising on the freeway on a 75 degree day the water temp stabilizes and holds right at 196 and the oil temp sits at about 201 ... on a really hot day (95 plus) coolant stays about the same but oil will sit at about 210.

HTH

 

That was my understanding of the situation.

 

Wish that could be an explanation, but there's no more than an 18" difference in height between the oil temp gauge and the water temp.
It's not possible to have that much of a diff in temp in a heated garage. There are no real drafts in this garage, it's fully insulated.

What is the diff in temps on these gauges before you start the car, after it has been sitting overnight?

Thanks,
Joel

 

Joel, in my garage the difference is about 10 degrees between water and oil temp at start-up. My garage isn't heated, as its not really necessary here, because about the coldest my garage gets in the winter is in the low 40s (My place is a two story building with the garage built into it ... rooms above the garage) and that's on about our coldest nights.

Thermocouples are, on average, accurate to about +/- 1.5 degrees in accuracy. If they are very old that can deviate from that.

see:

http://www.microlink.co.uk/tctable.html

and

http://www.temperatures.com/tcs.html

for WAY more detailed info on thermocouples (temp sensors, as I'm sure you recognize).

Again I've always written off the diff between coolant and oil sensors as a combination of things ...

The coolant sensor is higher, and above it is an insulating blanket built into the hood. It's gonna trap heat under the hood.

The coolant sensor is installed in the head ... in other words surrounded by a LARGE amount of metal, which is gonna change temperature more slowly than the oil temp sensor, which kinda hangs off the oil filter mount.

While it may seem hard to believe, in almost any room in a house it is not unusual to have a 10 degree (or even more) difference between ceiling and floor temperature. Add in the fact that the insulated hood liner is gonna trap heat under the hood ... a 13 degree difference just doesn'tt seem that far out of line.

Worst case ... say your oil temp sensor is off by 10 degrees (highly unlikely) ... from what I've read about thermocouples that error would be constant throughout the measures temp range. A thermocouple will not read +5 degrees at 40 degrees and +100 at 200 degrees. it will be off by +5 degrees at either temperature.

HTH

Go Oracle !!! Store it in a database and really track it ...

 

The temp sensors used in cars are typically not thermocouples, they are less accurate thermistors (a resistor which changes resistance with temperature). A thermistor is a non-linear device, and is selected to provide the best accuracy around the normal operating temperature of interest (around 160 to 250F for the oil and water temp sensors) The accuracy at the low end of the range is pretty poor, maybe off by 10 to 15%. It is therfore not surprising that the water and oil temp sensors are off by that much when the engine is cold.

 

[QUOTE=BlackZ06;1559634828]Joel, in my garage the difference is about 10 degrees between water and oil temp at start-up. My garage isn't heated, as its not really necessary here, because about the coldest my garage gets in the winter is in the low 40s (My place is a two story building with the garage built into it ... rooms above the garage) and that's on about our coldest nights.

Thermocouples are, on average, accurate to about +/- 1.5 degrees in accuracy. If they are very old that can deviate from that.

see:

http://www.microlink.co.uk/tctable.html

and

http://www.temperatures.com/tcs.html

for WAY more detailed info on thermocouples (temp sensors, as I'm sure you recognize).

Again I've always written off the diff between coolant and oil sensors as a combination of things ...

The coolant sensor is higher, and above it is an insulating blanket built into the hood. It's gonna trap heat under the hood.

The coolant sensor is installed in the head ... in other words surrounded by a LARGE amount of metal, which is gonna change temperature more slowly than the oil temp sensor, which kinda hangs off the oil filter mount.

While it may seem hard to believe, in almost any room in a house it is not unusual to have a 10 degree (or even more) difference between ceiling and floor temperature. Add in the fact that the insulated hood liner is gonna trap heat under the hood ... a 13 degree difference just doesn'tt seem that far out of line.

Worst case ... say your oil temp sensor is off by 10 degrees (highly unlikely) ... from what I've read about thermocouples that error would be constant throughout the measures temp range. A thermocouple will not read +5 degrees at 40 degrees and +100 at 200 degrees. it will be off by +5 degrees at either temperature.

HTH

Go Oracle !!! Store it in a database and really track it ...
QUOTE]

Thanks everyone, the discussion does alleviate some of my concerns about non-linearity of readings as oil temp gets into the real operating range. As an aside, there is no hood blanket on the car, and I had the hood opened, so there's no heat trapped. Temp in the garage is constant, within 2-3 degrees.
While there can certainly be a noticable difference between floor and ceiling in a room, that's normally about 8'. We're looking at something around 12" here...

Thanks,
Joel