Do what you feel comfortable by your own intuition.
Ila fuata ushauri wa watalaamu ambao Ni mechanical Engineers ,ama fundi gereji wakubwa wanafanya kazi kitalaamu,chukua sample Kama tano ama kumi baadaye average Basi unapata precision experimental data ufanye conclusion about durability, quality, affordability, management, services, repairs,spares,oil consumption, mechanical strength in case of head on collusion, horse power, endurance to work long than other.
Nimeshauri kiuchumi na kisayansi na na hesabu Nimetumia branch ya probability