This is actually a purely rhetorical question because the track duty higher viscosity engine oil recommended by the current Corvette program genius in charge, +Tadge Juechter can indeed contribute to much higher than expected engine operating temperatures.
How does this work? It is not very complicated, the viscosity of engine oil is temperature dependent and the viscosity number goes down as the temperature increases. The conventional automotive wisdom dictates that the heavier the oil grade the higher load it can support. This protection is of great importance to crankshaft and connecting rod journal bearings, as well as other narrow regions such as between the cam and follower on flat bucket tappets.
Of course, the protection does not come free, as a matter of fact, the price that is paid is the decreased fuel economy (higher energy is required due to higher molecular shear forces).
But... there is another aspect to higher grade oil, something that apparently Juechter, the engineer extraordinaire and his crew forgot to acknowledge: viscosity dependent oil thermal conductivity and heat dissipation properties. In a nutshell, the higher the viscosity of engine oil, or any other fluid, the higher the heat retention becomes. To put it in simple terms, thicker fluids become HEAT SINKS sorts and become more difficult to cool off due to higher internal forces.
Typically, this is not an issue with NORMALLY ASPIRATED and sufficiently cooled internal combustion engines WHEN AND IF the oil operating temperatures are well controlled. However, this aspect becomes a big problem with turbocharged and even more so, with the supercharged engines (supercharging is parasitic by definition and can create substantial load on an engine).
Apparently, Juechter chose to ignore this part altogether and the results are quite disasterous, with 320 degree temperatures becoming a norm instead of exception, WELL AHEAD OF HOT SUMMER HEAT!!!
Interestingly enough, the two measuring sticks Juechter likes to use, Nissan GTR and Porsche 911 Turbo use 0W-40 grade, without any distinction between track oriented and street driving, without experiencing even a fraction of overheating issues as the newest +General Motors flagship Z06 has to deal with on daily basis.
Considering the high potential of LT1 and LT4 turds to desingrate at will, it is perfectly understandable that Juechter would be resorting to using such heavy grade of oil as track requirement but... this clown forgot to account for the fact of automotive life and in the most idiotic way, designed such a shitty cooling system that it does not even suffice for the normally aspirated LT1 equipped cars.
Of course, there is considerably more to this problem but this is something best left for another day.
Incidentally, maybe clown Juechter should familiarize himself with the concept behind NAPALM and its effectiveness. In fact, maybe someone should drop some napalm on his ass to help him realize how much he fucked up his MOST TRACK CAPABLE CORVETTE EVER on this account alone.
320 degrees is way way to hot, even Mobile 1 starts Thermal Breakdown way before that. The oil might still protect to a much higher temp, but oil is a compound so some of the additives will basically turn to smoke. Check this link out, the Mobile 1 that was tested did very good, but still started to breakdown a 265 degrees.
ReplyDeletehttp://www.speedtalk.com/forum/viewtopic.php?f=1&t=31363
If I owned one of these cars, I would change the oil every 3,000 mile min or whenever the oil temp hit over 260.
Absolutely agreed although this was not the point of this entry since hopefully everyone realizes this part. This car's cooling system was designed to support 5W-30 oil while the engine internals cannot be protected without resorting to 50 grade while under track duty-a great recipe for failure. GM should really remove the track 50 grade recommendation and stop advertising this car as a track capable. Making these claims is nothing short of fraud.
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