Ummm a 4 year degree is usally a humanities degree.. or 
a business one... 

Engineering degrees (if you are custom making one 
especially( can take 4, 6 or even 8 years for highly 
specialized ones ( like advanced particle physics and 
the like) 

Plus Keiichi _was_ working in ceramic engine technology 
in the shop.. ( a very hot new technology in internal 
combustion engine tech) so I think it's pretty 
reasonable to assume that a 6 year degree might be in 
the offing.. with the last 2 years being somewhat sparce 
in the classroom time ( the classes he might need are 
only offered one time in the school year... and conflict 
with other classes that he also needs.. and they are 
only offered one time in the year) 

Just a few thoughts on that.