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Thread: Motor oil temperature

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    Motor oil temperature

    Since my 1.0L stripped-naked MT model has practically no instruments other than speedo and fuel level, I wanted to do a few measurements of water and oil temperature, purely out of curiosity.
    The following readings were taken with two thermometers, one on the upper region of, and directly on the cylinder head, and the other one directly on the oilfilter. For sake of getting an accurate reading, the area around each sensor was additionally padded or wrapped with a rag, with each sensor directly touching the metal.

    Conditions: Temperatures taken with a 3/4 grille block, after more than an hour's drive on the highway at normal speed and 24-26°C outside temperature, car has roughly 60 000km and 0W20 oil with ILSAC GF-5 classification. The measurements were verified by swapping and repositioning both sensors and rereading the temperature some time and some kilometers later.

    I measured a cylinder head (water) temperature of 89°C (thermostat opens 87°C), and an oil temperature of only 78°C.
    What surprised me most was the modest oil temperature, much lower than with similar sized cars and highway conditions. With that sort of oil temperature, we can expect the bearings and oil seals to last a long time.


    Last edited by foama; 05-20-2018 at 08:34 AM.

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    Nice report foama. What prompted this?

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    Quote Originally Posted by Eggman View Post
    Nice report foama. What prompted this?
    In Europe small cars are common, and quite a few get very high oil temperatures up to 150°C while highway driving! This includes many engines of a certain maker that we have heared more about recently.
    Generally, cars such as VW Golf/Rabbit/Polo have no such issues because they are made with water/oil temperature exchangers as standard, which is what makes their engines so suitable for long and fast highway driving.
    Since our Mitsubishi don't have that feature, I was just curious how good or bad this little engine was designed.
    Last edited by foama; 05-21-2018 at 07:12 AM.

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    It would be nice to access the oil pressure reading (and other parameters) off the OBD-II port. I'm not knowledgeable enough to figure it out.

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    Administrator Daox's Avatar
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    Wow, that seems quite low for oil temps. Nice though.
    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

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        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)


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    Quote Originally Posted by Eggman View Post
    It would be nice to access the oil pressure reading (and other parameters) off the OBD-II port. I'm not knowledgeable enough to figure it out.

    It would be nice if someone who has the equipment could give us some more figures...

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    Moderator Eggman's Avatar
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    It is my understanding that many parameters are mandated by the OBD-II specification. Oil pressure is not and is therefore an OEM parameter. It can be difficult to figure out how to map it because the PID varies from one manufacturer to the next.

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    Still Plays With Cars Loren's Avatar
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    Oil pressure is very likely not monitored by the ECU in a cheap economy car. There will be an on/off pressure switch that will trigger at something like 5-7 psi. (and it probably goes to the ECU, which activates the oil light... and you can probably monitor that via OBDII for what it's worth) But, no actual pressure reading. Oil temperature wouldn't be monitored in any way. If your oil temperature goes too high, coolant temp will follow... and eventually, our temperature light will come on, because we don't even have a temp gauge!

    But, cars have evolved to this state because they have been designed and built to be extremely reliable. We don't NEED a temperature gauge. We have a light that lets us know the car isn't warmed up yet, and one that lets us know it's too hot. All we need to do is make sure we keep the car well-maintained, and it will take care of us.
    Simplify and add lightness.

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    That's a good point Loren. I figured that the MIVEC system would somehow need to know the oil pressure since it's hydraulically actuated, but I guess not:

    ENGINE OIL PRESSURE CHECK

    1.Check engine oil level.
    2.Remove the engine oil pressure switch.
    3.Install the oil pressure gauge.
    NOTE: Use an adapter of PT 1/8 thread.
    4.Run the engine to warm it.
    5.After the engine has been warmed up, check that oil pressure is within the standard value.
    Standard value:
    At idle: 29 kPa (4.2 psi) or more
    At 3,500 r/min: 294 - 686 kPa (42.7 - 99.4 psi)
    6.Remove the oil pressure gauge.
    7.Install the engine oil pressure switch.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    Still Plays With Cars Loren's Avatar
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    Oil pressure varies (a lot) with RPM. Usually something on the order of 10 psi per 1,000 rpm. So, you'll have 8-10 psi at idle, and maybe 60-90 at redline.

    An oil-pressure driven cam advance system has to be built to deal with that kind of variation. Which their specs would indicate. "Little bit of oil pressure at idle" (very little, because our engine can idle at a very low speed and uses super light weight oil), and "big wide range of acceptable pressure at mid-rpm".

    The oil pressure measurement built into the car is just a fail-safe for catastrophic loss of oil pressure. Like, something broke, or you somehow ran it out of oil.

    If you ended up with "lower than normal" oil pressure, at a higher-than-idle RPM, it wouldn't matter too much except for maybe the MIVEC system. If it were low enough to effect that, then you'd get some kind of a failure code on that system. "Cam timing out of range" or something like that.

    The way oil pumps work, they're a "constant volume" pump, so oil pressure will always be directly proportional to RPM. So, as long as you're meeting spec at idle (you're not tripping the "too low" sensor), you're almost guaranteed to be within spec at higher RPM.


    Simplify and add lightness.

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