Mazda 6 Service Manual: No.13 knocking/pinging-acceleration/cruise

No.12 lack/loss of power-acceleration/cruise

No.14 poor fuel economy

Other materials:

Mazda 6 Service Manual: Contact Authorized Mazda Dealer and Have Vehicle Inspected
If any of the following warning lights or the indicator light turns on/flashes, the system may have a malfunction. Contact an Authorized Mazda Dealer to have your vehicle inspected. ...

Mazda 6 Service Manual: Recommendations for Shifting
Upshifting For normal acceleration and cruising, Mazda recommends these shift points: *1 Always observe local speed limit regulations. Downshifting When you must slow down in heavy traffic or on a steep upgrade, downshift before the engine starts to overwork. This gives better acceleration w ...