Date: 201809
Light: Daylight
Aircraft: B737 Next Generation Undifferentiated
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Aircraft component: Powerplant Fuel System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Troubleshooting
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance; Inflight Event / Encounter Fuel Issue
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: My concern is that some MAX 8 aircraft are burning significantly more fuel than what is calculated on the Dispatch release. Perhaps the fuel bias on these aircraft needs to be re-evaluated. On this particular flight; the burn rate was so high that the Pilots referred to the MAX AOM (Aircraft Operator Manual) to look up what constitutes a fuel leak. Our flight plan fuel was for a burn of 21;600 pounds from push to touchdown. Our actual burn was 22;900 pounds (actual fuel load of 28;100 at push minus our 5;200 pounds at touchdown. We pulled into the gate with 5;000 pounds). This was 1;300 pounds more fuel burned than planned.Other than a direct to ZZZ shortly after departing ZZZ1; we flew the flight planned altitude and routing. I also slowed to .76 Mach a couple of times for pockets of turbulence. Winds were close to flight plan and there was minimal off-course maneuvering to avoid a couple of buildups. Based on another long MAX 8 flights where we burned more than flight plan; I kept a detailed fuel log this flight. We pushed with 700 pounds fuel more than flight plan. Fifty minutes into the flight we were plus 500 pounds of fuel over flight plan. At 1+20 into the flight; we were plus 300 pounds. At 1+49 we were at the calculated flight plan fuel. Eleven minutes later we were at -300 pounds from flight planned fuel. Around that point we contacted Dispatch through ACARS to let them know our fuel was not trending well. We got into the books and ran the Fuel Leak QRH just in case. The flight attendants scanned the engines and the wings. Everything checked out ok with respect to the QRH; except we had an unusual fuel burn. Dispatch; the FO (First Officer); and I came up with a plan to update our status over ZZZ and also over ZZZ2. At 2+11; we were -500 pounds for fuel. The fuel trend stayed constant at -500 pounds from flight plan for the duration of the flight from that point onward. The weather was VFR at ZZZ3 so we elected to continue over ZZZ and also ZZZ2. I was concerned as my calculations had us landing with less than 5;000 pounds. Dispatch said his calculations had us landing with 6;300 pounds. Dispatch was very helpful throughout the majority of the flight providing updates on weather and asking our fuel status. Dispatch also asked that I call him after landing. We landed uneventfully other than fuel being 900 pounds lower than the Dispatch Release after flying the flight plan. After landing; I walked around the aircraft and went into the main gear well. My concern was a potential fuel leak. I noted none nor any abnormal fuel smells. After that; I called Dispatch and we had a conference call with Maintenance. The Maintenance Controller said they were noting that several MAX 8 aircraft are not fuel efficient. He said they think the Boeing-recommended engine cleaning cycle is not frequent enough. I was told during this call that when the LEAP engines are dirty they lose all of their efficiency. If this is the case; shouldn't the fuel bias on these aircraft be adjusted accordingly? From now on; I am going to plan on an extra 400 pounds per hour of fuel on each MAX 8 I fly on a leg longer than two and a half hours.




Synopsis: B737 MAX-8 Captain reported the engine fuel burn was higher than expected.