And put it this way:

- 6001 to 6007 (B9TL / 3y4m in service) have dealt with the X1 day in and day out and with the hilly Old Durham Road and Washington Highway well, sometimes with standing room only. Result, no engine replacements required!

- 7616 to 7627 (VDL DB300 Cummins ISBE 6.7 / 2y11m in service) hav coped OK but struggled with no hills between Newcastle and Blyth. Only mainly started dealing with express work after the 308 got B5LH's. Result, several engine replacements and rebuilds required.