I was wondering what degree, if any, do Synthetic Engine oils reduce underhood temperatures over their conventional counterparts? I also wonder if there is a reduction of underhood temperatures, does this benefit an automatic transmission(independent of using Synthetic transmission Fluids)
Engine temperatures synthetic vs conventional
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Scangauge II provides real time engine temps among other things.
The engine temp is controlled by the thermostat so I don't know how the temp could change..
Synthetics don't reduce engine temperatures. However, synthetics can withstand higher temperatures. This is why Chevy used synthetic oil in 1997-2004 Corvettes, it was cheaper than putting in an oil cooler. Interesting enough, same year Camaroes (with same engine) did not need synthetic due to location of radiator air intake (Corvette is lower and sucks in hotter air off road in summer).
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High levels of friction modifiers and lubricity improvers will reduce temps. Thinner oils for the same application (aka synthetics), will reduce temps as well because they do the same job with less internal fluid friction.
Actually synthetic oil can reduce engine temperature. It does so by reducing friction which causes heat. It isn't a huge drop but you can see a small drop with it. I have seen it( measured with a temp gauage ).
People will claim it is impossible because the t-stat controls the temp but that actually is a flawed argument. The t-stat controls the lowest temperature for the motor/coolant but it does not mean that is exactly where the engine temp remains. If you run a 190 degree t-stat that simply means when the engine reaches 190 degrees it opens allowing coolent to circulate. The actual temperature will be higher( hitting 200+ ).
So, synthetic oil can reduce your temperature a bit. However, it will not reduce it below the point the t-stat opens.
Assuming your thermostat is working, and likewise other parts of your cooling system, then the engine will pretty much stay at the proper temp regardless of oil.
I find synthetic oil helps a lot when its cold like today (6 F at my house) and you are cranking the engine over.
Synthetic oil will reduce oil temperature but it's not a huge amount. It will not, in my experience and according to what I have studied, deliver a reduction in coolant temp that you can notice on a standard coolant temp gauge (like: "Wow! My coolant temp went down 20 degrees!").
My truck has separate oil and coolant temp gauges and I have been monitoring these things over several types of oil over the past few years. I did see about a 3-5 degree drop in my everyday running oil temp going from conventional 5W20 to synthetic (MC to RP) . I also saw a 5-10 degree rise in running oil temp going from the synthetic 5W20 to a mineral 10W30 (RP to MC HDEO). By "running oil temp" I mean the stabilized oil temp over a measured course with a measured load. That exact temp varies according to ambient temp and engine load but I know the variables now and have a baseline. In any of these cases, I do not see lower or higher coolant temps (on a very accurate Isspro stepper type gauge). With a large drop in oil temp, you probably would see a drop in coolant temp.
Also, I think the amount of the reduction in friction(and temp) from syn to conventional would depend of the amount and type of FM's used in the conventional oil to meet that "Energy Conserving" standard. I think with enough FMs in a good mineral base oil, it could really mimic a syn that wasn't FM'ed. Being additives, the FMs will eventually degrade while the syn base oil would retain those "slippery" characteristics more or less permanently. And then, you may have FM'ed syn oil. There are differences in FMs and how long they last but I don't know exact details
IMO, a small reduction of oil temp doesn't transfer to anything noticeable on the coolant temp side in normal situations. It does reduce the overall cooling system load a little and in extreme situations, you may see something noticeable but it wouldn't be much. I see it as one of the bennies you get with a good syn but by iteself, it's not all that significant for most of us.
You can see more of a temp reduction with gear oils, in my experience. Going from a mineral (usually Gp 1 or II) to a syn (PAO) delivered a 15 degree drop in oil temp over a measured course and with a specific load in each case, and with identical ambient temps.
If synthetic oil is producing lower oils temps, is that because of less friction or a lower ability to cool bearings? Do synthetic formulations have a different specific heat index (less temp increase for the same heat removal)? Does synthetic oil conduct heat poorly as compared to conventional oil (absorbs less heat, but has similar specific heat index)? Is is possible that synthetic oil conducts heat better than synthetic and therefore dissipates heat from the oil pan better than conventional oil does?
Is it known that the lower temps of engine oil is caused by the same mechanism as transmissions?
I think of heat in the differential as being caused by friction alone. Less heat in the oil would indicate less friction.
I think of heat in the transmission as being cause by friction and conduction from the engine block. Less heat in the oil may indicate less friction.
However, I think of heat in the engine as being caused primarily from combustion. Lower temperatures in the oil may not be primarily related to friction. I am not claiming to be right, but I would like to understand these observations better.
Had a friend that switched to Red Line from I assume conventional and noticed about a 20 Degree drop on a late 70s Ford. Probably back before the dummy gauges were installed.
I've noticed on our Jeeps that synthetic runs about 1 needle's width cooler than conventional. Yah, that's not scientific or any hard number, but it's noticeable especially in summer.
The post above referencing thermostat....the thermo opens at a certain temperature, the average temp of the cooling system fluid can vary quite a bit, from ambient all the way to a point that's actually above the boiling point of the fluid. (pressurized cap keeps it from boiling)
When I first used AMSOIL, back in the Dark Ages (1977), i ran about 100 miles down the interstate and stopped to check the oil.
The dipstick was warm to the touch, vice hot as in the past.
Was the underhood temperature different? I have no idea.
But the oil temperature was definitely lower. And before I got home, the gas mileage had jumped by 2 mpg.
Now, the standard oils are a whole lot better now, so I have no idea if this still holds true. Heck, haven't run anything but AMSOIL since then.
When I had M1 0W40 in MB E430 few years back, the coolant temperature was about 190-195F at highway speed of 70-75 MPH. It had synthetic xW20 since summer 2008 and since then I observed the temperature dropped to 182-185F at similar speed.
I'm not sure if synthetic of the same grade will make engine runs cooler than dino or not, but thinner oil does.
i might lower the temps enough to help the thermostat cycle less often... who knows
Hi,
oilstudent24 - The differences if any will be realatively small - they may also be isolated - well this is what I have found!
There are many ways to check this as an "enthusiast" and many more in the real world of systematic field testing. In field testing the variables are immense! Vehicles set up for on-line recording of temperatures in certain "hot spots" can also produce quite conclusive results
In a Lab, the controlled testing and replication enables some keener conclusions - and these are!
I have used an IR reader on various engines (Porsche and MB cars and various bikes) carefully selecting spots around the engine that enable quick and easy access. I have recorded some hundreds of readings over some years. Variances have been almost imperceptable!
In the case of driveline lubricants however there is typically a measurable difference. This in my case/testing process is typically within a 10-25C reduction when using the correct synthetic lubricant. This reduction extends the life of various seals etc - and of the lubricant. In my case lubricant(s) were still suitable for use at up to around 1.2m kms. The limiting factor was the wear metal limits and not the condition of the lubricant
IMO using an incorrect viscosity lubricant may possibly have a greater affect on an engine's temperature!
If comparing base stocks of the same viscosity I'm not too sure synthetic reduces friction compared to mineral. I need someone to point me to a white paper or someone to confirm this. Thanks
Originally Posted By: tudorart
If comparing base stocks of the same viscosity I'm not too sure synthetic reduces friction compared to mineral. I need someone to point me to a white paper or someone to confirm this. Thanks
Originally Posted By: hooligan24
i might lower the temps enough to help the thermostat cycle less often... who knows
Originally Posted By: GMorg
If synthetic oil is producing lower oils temps, is that because of less friction or a lower ability to cool bearings? Do synthetic formulations have a different specific heat index (less temp increase for the same heat removal)? Does synthetic oil conduct heat poorly as compared to conventional oil (absorbs less heat, but has similar specific heat index)? Is is possible that synthetic oil conducts heat better than synthetic and therefore dissipates heat from the oil pan better than conventional oil does?
Is it known that the lower temps of engine oil is caused by the same mechanism as transmissions?
I think of heat in the differential as being caused by friction alone. Less heat in the oil would indicate less friction.
I think of heat in the transmission as being cause by friction and conduction from the engine block. Less heat in the oil may indicate less friction.
However, I think of heat in the engine as being caused primarily from combustion. Lower temperatures in the oil may not be primarily related to friction. I am not claiming to be right, but I would like to understand these observations better.
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