Fundamental question RE: purpose of engine lubricant is to lubricate (reduce mechanical friction is the primary goal) and also serve as a medium in transferal of heat off of various engine parts (bearings and other friction surfaces, moving parts, cylinder walls, various different points on pistons, etc.)
In a water-cooled spark ignition internal combustion engine, water, as a form of coolant, absorbs approx. 36% of total power loss through water heating (water jacket), whereas friction comprised of 6% of power loss.
http://ffden-2.phys.uaf.edu/102spring200...%20-%20Main.htm
http://ffden-2.phys.uaf.edu/102spring200...er%20losses.htm
Due to the fact that in a water-cooled IC engine, coolant takes on about 1/3 of the entire thermal energy loss and also serves as the primary medium for heat conduction/transferal (more surface area for water jackets to absorb/transfer heat away from critical components such as cylinder head, engine block, intake manifold, spark plug hole area, etc. than that of the motor oil lubricating area), only relatively small portion of heat transfer/conduction performed by the engine oil when served as lubricant (typically only a few % points).
Let’s shift the focus to engine lubricant RE: whether there is additional benefits in friction reduction when switching from regular motor oil (of the same viscosity and API grade) to equivalent synthetic lubricant of the same viscosity and API grade would result in significant friction reduction to sufficiently lower the energy loss in terms of friction:
http://me.engin.umich.edu/autolab/Projects/SIEngineTribo_aux2.html
(*FMEP-Friction Means Effective Pressure, referencing to SAE paper 2002-01-2681 research paper*)
Look closely and you shall see that the difference between oil sample 1 and 2 (mineral 5W30 vs synthetic 5W30) FMEP in bar unit is pretty much less than 0.05bar (nominal), which is relatively insignificant (taking baseline oil 1 vs oil 2 as an example), your best case scenario would be around 3~4% of difference over the denominator of 1.2bar (baseline) in terms of friction reduction.
Now, given the fact that about 6% of the total energy comes in the form of friction within the engine, the additional 4% savings in form of friction reduction in 6% works out to less than 1% of energy gain in the total energy conversion.
So, you are telling me that your gain in that already minute gain (works out to approx. 4%) in that cumulative 6% friction energy loss in IC engine is going to have a significant impact to the 1/3 (36%)energy loss to the coolant (thermal management) is going to be obviously enough to cause an obvious needle deflection on your water temperature gauge on your dashboard?
The only exception to the rule would be extreme heavy duty IC engine which would require further heat exchange/conduction to maintain steady operating temperature mainly on mechanical(friction) parts, or air-cooled IC engines that would require more heat-transferral properties from engine lubricant to assist the relatively poor heat-conduction properties of air.
Also, more significant impact may be perceivable if your experimentation comprised of switching over from higher viscosity mineral engine oil to lower viscosity synthetic lubricant.
My proofs are in various university research papers and SAE papers....
now it's your turn to prove me wrong.
