Save pound’s by having the correct fuel mixture! Fuel mixture adjustment can be a hit and miss affair. Not with Colortune. This easy-to-use tool temporarily replaces one spark plug at a time providing a window into each individual combustion chamber. Adjust the mixture with the engine running until the correct bunsen blue combustion colour is achieved – job done. Works on carburettor fed and fuel-injected engines. Pays for itself in petrol savings.Its unique design maintains compression while the engine runs and ensures correct firing of the mixture. Gunson G4074 Colortune Single Plug Kit (14mm thread) fits most standard petrol engines. Colortune adaptors are also available. See the How do I adjust the carb on my vehicle ? article in the Technical Articles section