OVERKILL
$100 Site Donor 2021
The Corolla is the exception, not the rule, and as Zee noted, there would have been design accommodations made (like wider bearings) to facilitate the use of 0W-20. Though it's telling that it doesn't spec 0W-16 or 0W-8 like most other things Toyota at this point.Nonsensical response unsupported by facts. Just off the top of my head:
Corolla GR is 0w20. 185HP per liter.
New Porsche GT3. 0w40. 125 HP per liter.
- GM has historically recommended M1 15W-50 in the Corvette if going to the race track, but 5W-30 for daily driving.
- Ford spec'd 5W-20 for the "regular" version of the Mustang GT, but 5W-50 for the same car, with the same engine, in "Track Pack" trim which had different thermal programming.
- The FCA SRT vehicles all spec 0W-40, while the non-SRT HEMI's all spec'd 5W-20 or 0W-20.
High performance track-oriented vehicles with limited production volume can be spec'd a greater safety margin with little penalty to the parent company's CAFE fees. Depending on power density, sump volume, oil cooling capacity and ultimately lubricant temperature measured during testing, the grade with sufficient margin is determined for these applications. When the manufacturer is only moving a few thousand, this really has little impact on CAFE penalties, and consumers are generally paying a premium for these vehicles anyway.
Daily driver oriented vehicles with high production volume are more likely to be spec'd less margin in order to increase CAFE and reduce the penalties/fees as much as possible. When you are moving hundreds of thousands of a powertrain, every little bit of fuel economy counts. This reduced margin is balanced by the use of coolant/oil heat exchanges (which also bring the oil up to temperature more quickly, improving fuel economy) and software-driven safety mechanisms that can reduce output in the event the oil gets above safe operating temperature.
There's probably no better example of this than the aforementioned Ford Mustang situation. The "Track Pack" version, that spec'd 5W-50, had a big oil cooler and could be readily tracked with no loss of performance. The "regular" version, which spec'd 5W-20, with the SAME engine, would readily go into limp mode (thermal castration) if pushed for too long, due to the oil temperature getting too high to provide adequate viscosity and lubrication. This highlights, quite handily, the compromise made by going with the lighter oil, and the mechanism employed to ensure that this was safe. This is because the vast majority of Mustang GT's sold would not be of the "Track Pack" variant and very few of them would ever see a racetrack, so it was a reasonable compromise.