Days of $2/qt oil are over. Seems like $3/qt is the new "cheapest oil" category standard. One hero stands tall in that category - Super Tech Heavy Duty 15w40 at $11.74/gallon, which works out to $2.94/qt. Or $3.58/qt if you buy in 1qt bottles. Or $2.92/qt if you buy in 2-gallon jugs.
Realistically - this oil can successfully be used in a 1-cyl air cooled motorcycle, a 3-cyl Mitsubishi Mirage, or 16-cyl Bugatti, as well as everything in between. May not be the correct spec, but it will do the job, as long as it's within the temperature limits of 15w40 (which in general is roughly -15C to +40C or 5F to 104F), and shouldn't cause any oil-related issues that have to do with level of protection that this oil offers. Some engines have factory defects, and no oil can stop those from blowing up or spinning a rod bearing. So we'll leave those out of this exercise (BMW V8/V10 for example).
The Mental Exercise: in a wide range of automotive engines and vehicles (ignoring motorcycle engines with shared sump) can we come up with scenarios/vehicles where Super Tech 15w40 won't be able to protect the engine well enough? For the sake of the exercise let's say that said engine won't see ambient temperatures outside of 15w40 range, and engine isn't a subject to overheating issues. Period of protection needed is 150k miles with 3k-5k OCIs. Go.
Realistically - this oil can successfully be used in a 1-cyl air cooled motorcycle, a 3-cyl Mitsubishi Mirage, or 16-cyl Bugatti, as well as everything in between. May not be the correct spec, but it will do the job, as long as it's within the temperature limits of 15w40 (which in general is roughly -15C to +40C or 5F to 104F), and shouldn't cause any oil-related issues that have to do with level of protection that this oil offers. Some engines have factory defects, and no oil can stop those from blowing up or spinning a rod bearing. So we'll leave those out of this exercise (BMW V8/V10 for example).
The Mental Exercise: in a wide range of automotive engines and vehicles (ignoring motorcycle engines with shared sump) can we come up with scenarios/vehicles where Super Tech 15w40 won't be able to protect the engine well enough? For the sake of the exercise let's say that said engine won't see ambient temperatures outside of 15w40 range, and engine isn't a subject to overheating issues. Period of protection needed is 150k miles with 3k-5k OCIs. Go.