Lo joined in near the end, claiming at his trial he had only delivered one blow to the face.
Adams, however, had kicked Mr Tupe's head "like a football" and punched and stomped him.
"There can be no doubt in your case the you killed Tamati Tupe," Justice Fogarty told Adams.
"There's no doubt that this prolonged assault by you was brutal, cruel and highly callous".
Adams had been drinking all day when he killed Mr Tupe, who the judge said was a "totally innocent young man who gave no provocation". He was in the area because his car had broken down.
That morning Adams' mother got up at 3am and from then on the family boozed away the hours. Adams estimated he knocked back 50 cans of pre-mix bourbon drinks and smoked half a tinnie of cannabis.
However, the judge believed Adams was remorseful for what he had done and gave him some discount in sentencing for his upbringing.
Justice Fogarty wasn't so convinced by Lo's remorse.
His lawyer Mele Tuilotolava said Lo had turned to God while in prison and wanted to make an apology in court to Mr Tupe's family. They decided they weren't ready for that.
Outside court Mr Tupe's brother, Eugene Tupe, said Lo and Adams deserved their sentences, while his uncle Takapari Waata thought they deserved more, whatever the judge imposed.
Several members of Mr Tupe's family spoke of the importance of family in keeping young people on track.
Today's sentencing brought the "sad and tragic case" to conclusion, police said.
Counties-Manukau Detective Inspector Dave Lynch said police wanted to pay tribute to Tamati Tupe, an "all round nice guy" who had a promising career as a mechanic.
Mr Tupe had turned his life around after a tough start, losing both parents at an early age, Mr Lynch said.His brother Maurice died in a car accident, and another family member who cared for him died soon after that.
"After growing up in these challenging circumstances, Tamati went on to become someone who was regarded as an all-round nice guy and had a promising career as a mechanic.
"His life and story could well have been an inspiration to us all and the fact he was killed in such a senseless and barbaric manner is a tragedy."
Mr Lynch thanked Mr Tupe's whanau for their assistance during the investigation and the trial process "which was no doubt difficult for them".