Originally Posted By: OVERKILL
Originally Posted By: WANG
The Track Pack and Boss 302 are presumably geared toward track days. It makes sense for the owner's manual to specify oil suitable for that application.
But they ONLY specify 5w-50. They do not recommend 5w-20 (like what is spec'd for the regular GT) when driven "normally".
Originally Posted By: WANG
All I am trying to convey is, if there is a viscosity requirement for a long and happy service life it is probably spelled out in the owner's manual.
Unless it can't be.
Originally Posted By: WANG
The citations that people have provided of "Track Pack" and "sustained high speed operation" and etc., are examples of what I'm saying. If there is a better recommendation, it's probably in the manual.
In the case of OP's cars, there was no such recommendation germane to his operating environment, that he made known to BITOG.
But that's exactly the point. The Mustang GT, which CAN and certainly HAS seen track duty, spec's 5w-20 and gives no options for anything above and beyond that. In fact Ford has thermal castration mechanisms in place to ensure it doesn't lunch itself if oil temps get high enough due to the spec'ing of a single grade for that car regardless of ambient or operating conditions.
However, you buy the same car but with the "Track Pack" options pack and all of a sudden you have an oil cooler and a 5w-50 requirement and don't run into the thermal castration mechanism.
I will conceed ignorance to this characteristic of Mustang GTs. This is a pretty solid example where, in the case of non Track Pack GTs, the owner's manual recommended oil does not offer adequate protection up to the maximum performance available from that engine. However, I have to wonder how many owners found themselves in a "reduced power mode" outside of a closed circuit due to elevated oil temperatures. I would also say that the difference between "adequate protection" and "inadequate protection" with respect to plain bearings is most likely the difference between catastrophic failure and continued service. There isn't a ton of middle ground.
Again, I was ignorant of this aspect of Mustang GT operating characteristics, and it is a compelling case for the owner's manual not necessarily making consideration for all possible operating circumstances of a motor vehicle. I wouldn't have expected that.
However, for the great great majority of the vehicle operating public, some guy going 10-15 mph over the speed limit in his Corolla in the middle of summer (I don't really care where) isn't likely to touch or come close to these limitations.
I would say that we are taking the OP out of context, but I pointed to the owner's manual as the best source of viscosity guidance under any operating conditions. Overkill pointed out a case where maximum engine performance wasn't available for extended periods of time using the only recommended oil in the owner's manual (Coyote Mustang GT), so that is a fair point of discussion.
If anyone has a similar example of engines/powertrains going into "limp" or "reduced power" mode due to excessive engine oil temperature, let us hear of them: