'90 L98: how is oil temperature determined?

[bradvette]

Using HVAC conversion codes, I only see #16 which means coolant temp, in degrees celsius, for my '90.

I see no digital redout capability for oil temp. How do I find out what my oil temps are - is there a formula or some other method of determination?

The almost useless analog guage, certainly inaccurate at best, always seems to indicate a lower oil temp than coolant temp.....although the reverse should be true.

 

[Aurora40]

The almost useless analog guage, certainly inaccurate at best, always seems to indicate a lower oil temp than coolant temp.....although the reverse should be true.

My 1987 with oil cooler had digital readouts, and the oil was usually cooler than the coolant. The only time it wasn't was after some aggressive driving. I suspect it could be where the temps are measured that make the difference.

 

[bradvette]

My 1987 with oil cooler had digital readouts, and the oil was usually cooler than the coolant. The only time it wasn't was after some aggressive driving. I suspect it could be where the temps are measured that make the difference.

yes that makes sense, thank you. does anyone '90-on know how to (digitally) determine their oil temps?

 

[Edmond]

yes that makes sense, thank you. does anyone '90-on know how to (digitally) determine their oil temps?

I thought they went with the partial digital and partial analog dash starting in 90...

 

[bradvette]

I thought they went with the partial digital and partial analog dash starting in 90...

yes you are correct; thats why its called a "hybrid" dash. has analog coolant and oil temp guages.....HVAC digital readout supports a coolant temp readout, but not oil temps that I know of. This is what I'm trying to find out.

 

[Aurora40]

yes that makes sense, thank you. does anyone '90-on know how to (digitally) determine their oil temps?

I would imagine if you had an OBD-I scanner of sufficient ability, it would be able to spit out the values for the oil temps. That varies by scanner/software, and of course the vehicle has to output it, but I'd bet the Corvette does. But this is just speculation, as I don't have a '90 (cough, yet, cough), nor an OBD-I scanner.

 

[drags1998]

As far as I know, There is NO WAY to get the oil temp.I do know on my car the oil temp is ALWAYS cooler than the water temp. My buddies 95 has a much better system that will give you all the info. that you would ever want!!!!!

 

[c4cruiser]

My 92 can show oil temps simply by pushing the Gauges button on the dash until the oil temp display shows up directly below the speedometer. The choices on my car are Volts, Coolant Temp, and Oil Temp. The temperature values will display in either Fahrenheit or Celcius.

90 was the first year for the new dash design and it (supposedly) featured a mix of digital and analog display. I also have the C68 Climate Control and I can display coolant temps in degrees Celcius by selecting Parameter 16.

 

[RonJ]

My 1987 with oil cooler had digital readouts, and the oil was usually cooler than the coolant. The only time it wasn't was after some aggressive driving. I suspect it could be where the temps are measured that make the difference.

My 85 with the digi dash shows that the oil is hotter than the coolant once it is completely warmed up, like cruising on the highway.

If the oil was cooler than the coolant, why is the coolant used to cool the oil?

For the cooler to be of any use, the oil would have to be hotter than the coolant, which is the case on my car. My two cents.

Ron ...

 

[Aurora40]

If the oil was cooler than the coolant, why is the coolant used to cool the oil?

For the cooler to be of any use, the oil would have to be hotter than the coolant, which is the case on my car. My two cents.

Right, but I don't think the cooler does much, nor is needed until the car really starts exercising. It was included with the Z51 package on my car, but was not included on all 1987 Corvettes. So it's quite possible that the oil cooler is not of use much of the time in regular driving.

But also, as I said, it depends on where it is measured. The coolant temp is likely measured in one of the cylinder heads, where it will be practically at its hottest. If you were to then measure it in the radiator, it would be a lot cooler. I believe the oil temp is measured by the oil pressure sender, though I could be mistaken. This is down quite low on the engine, and it's quite possible oil there is a lot cooler than the oil that's rolling down the rockers back towards the pan. In addition, the two sensors are calibrated towards a much different range of temps. So it could be "210" on the coolant gauge and "210" on the oil temp gauge don't equal the same real temp.

 

[RonJ]

This thread kind of perked my interest. Couple of things.

According to my service manual, the oil temperature sender is on the left side of the block directly above the oil filter. It is serviced with a dark green wire with a white tracer. I didn't look on my engine, but if they say so ......

I took the 85 out for a cruise, outside temperature around 70f. Cruising 50-55 mph in O.D., in about 25 minutes the coolant temp was 185f and the oil temp was 195f. I believe that is about the normal reading for my vehicle.

Ron ...

 

[Hib Halverson]

I don't think a 90 will display oil temperature through the hvac. Also, I don't think it will display it via the gages button. I think that feature was not offered until 91 or 92.

With a 90, I think you're stuck with the analog gauge which is usually horribly inaccurate. My advice would be to use some kind of temperature mesauring device (A Raytek IR termometer, for example) to read the oil temp in the pan at various gauge readings and make yourself a "conversion chart".

 

[-=Jeff=-]

I don't think a 90 will display oil temperature through the hvac. Also, I don't think it will display it via the gages button. I think that feature was not offered until 91 or 92.

With a 90, I think you're stuck with the analog gauge which is usually horribly inaccurate. My advice would be to use some kind of temperature mesauring device (A Raytek IR termometer, for example) to read the oil temp in the pan at various gauge readings and make yourself a "conversion chart".

The gauges display for digital readouts was first available in the 1992 model year. the 90-91 shared the same LCD display and the 92-96 shared a different LCD display. I have looked into this as I wanted to add that feature to the 1991 dash in my 89. the Oil display is also embedded in the code in the CCM to allow it to display to the dash.

 

[Hrtbeat1]

Jeff is right.


I found out that on the '90 and I think the '91 model the oil temp and the coolant temp come from the same sender unit. Passenger side in the middle of the block slightly below the plugs. How GM does this I'm not sure. I think it has to do with the embedded code in the CCM. The temps are not accurate being that they are analog guages.

 

[bradvette]

thanks guys, Hib and the later posts support my thoughts. and yes, my analog oil guage is particularly out of whack (I have a new oil sending unit), no matter how long i drive, the oil temps as indicated on the guage is much lower than the coolant temps......which is of course entirely incorrect in actuality.

 

[OLDCHEV]

My 1990 water temp sending unit for the analog gauge is at the front of the block right under the thermostat housing. The oil temp sending unit is right above the oil filter in a line that goes to the oil cooler. The water temp gauge always reads higher than the oil temp gauge.

I have shot both the cooler line and the upper radiator inlet with a Raytec Thermal Gun, the radiator is always hotter. The water sending unit in the passenger side head is to turn on the second fan (if A/C is off) at 240 degrees as a last resort.