4.2 Plugs Change Lower Mpg

[Notebook]

Hi All

Just had my plugs changed at a toyota specialist place that has done work on mine and a few friends cars. Always done a good job. However the mpg on my petrol 55 plate has dropped from 30mpg to 24. Will reset the computer that says mpg etc and double check. Can this happen untill the ecu etc catches up?

Thanks

[pmb]

They put in the Iridium plugs which cost about £50 a set I assume? When I had mine changed a couple of years ago the garage apologized for the cost of them which I knew about! I didn't notice a change in mpg when they were changed nor any ecu issues.

[Notebook]

Hi

plugs were £38.20

[anchorman]

They MUST be Iridium plugs or it won't run right.