More than 5,500 participants are now using the scheme, which is available to sign up to free online at its website.
Bodyshops can now “bank” whole boxes instead of just the tops to exchange for reward points and prizes such as NGK branded T-shirts, Nintendo Wiis and Sony Playstation 3s.
Brian Childs, deputy managing director of NGK UK, said: “The most important investment to the Box Clever scheme has been to the website.
The new site allows garages to check their accounts online and order their free gifts there and then.”
NGK UK sends special postage-paid “BoxBags” that garages can use to return their used spark plug boxes.
Box Clever even has its own touring promotions girl who visits garages around the UK to market the scheme.
NGK has also updated its latest spark plug catalogue, which is available to view online.
It now provides its products as original equipment for the new Fiat 500.