All your buddy is doing is hurting his motor.
If the truck is not designed to run on "the good stuff", its not going to run right. Vehicles that are designed to run on the good stuff typically have a higher compression ratio and tighter tolerances, and are typically geared to high horse power and performance. If the vehicle is not designed to run on it, it can not completely and efficiently burn the air/fuel charge. This means that your converter has to work double time, and you risk plugging up your converter if it becomes over loaded with this unburnt fuel.
I used to be a certified emissions tech here in Southwestern Ontario.. People would bring their car in for an emissions test, and it would fail. They would take it, throw an air filter in it, fill it with premium, take it for a boot to get it hot, and bring it back. I would put it on the dyno and re-test it, only to have it fail with MORE emissions than their previous test, mainly HC's (Hydrocarbons), or in simpler terms, raw fuel.
Just sayin..
Jay
