Narrative:

While verifying the FMS was programmed correctly I noticed a large variation in expected fuel burn (from the release) and actual fuel burn (on the FMS). The following is a breakdown of the fuel comparison between the release and the FMS.in addition; the estimated extra fuel on board after burn off to ZZZ and the alternate ZZZ1 would had only been 170 lbs. According to the release; I should have had at least: 1034 lbs. This is a difference of 864 lbs between the extra fuel calculated on the FMS and the extra the release calculated.after realizing the discrepancy I called our dispatcher. I informed her that I would like to add 500 lbs of fuel (following procedures set forth in the fom) as the FMS was calculating the fuel numbers listed above and as seen on the screen shot labeled FMS pre-takeoff. It took a little more explaining but I was told that I had enough fuel to make the trip to ZZZ. I informed her that I would not have enough fuel to get to ZZZ1. The 170 lbs of extra fuel mentioned above did not include engine start and taxi which was estimated at 285 lbs as seen on the release. Again; she; perhaps confused; still said that I had enough fuel and was not authorized to add fuel.after insisting some more; she took the matter to her supervisor whom stood by our dispatchers decision to deny the additional fuel. Both our dispatcher and the manager indicated that my FMS must be producing an error and that they would be unable to approve the additional fuel. With the weather in ZZZ improving and looking as if IMC conditions were about to be lifted soon; I decided that the odds of going to the alternate were slim and elected to depart.after landing in ZZZ; I recorded a landing fuel load of 2;800 lbs which was almost exactly what the FMS originally estimated prior to take off. Which meant the estimate on the release was actually off by 671 lbs. I called our dispatcher to inform her of the actual landing fuel as soon as we got to the gate.after further review with our assistant chief pilot; we noticed that the extended flight plan portion of the release showed the fuel calculations ended at zzzzz intersection. The total distance not accounted for on the ZZZZZ1 2 arrival is 46 nm. From the furthest point on the approach (which we were vectored to): total distance not accounted for: 70.5 nm (46 nm + 5 nm + 19.5 nm)subtract the distance from zzzzz to ZZZ (via direct as planned on the release) 26.5 nm. * This number was accounted for on the release and therefore should be subtracted from the total distance not accounted for. Additional distance flown vs planned: 44 nm.at an average speed of 200 kts. (Usually 210 kts from zzzzz to final intercept followed by a speed reduction to 180 kts to ZZZZZ2 once on final) it would take approximately 14.5 minutes to fly the 44 nm at an estimated 2;600 lbs/hr (43 lbs./min *14.5 minutes) = 623 lbs. This is almost exactly the original difference I described above. The very next flight into ZZZ we noticed that the extended legs section of the release had the full arrival and the actual fuel burn was almost exactly as planned.the primary cause of the event was me not exercising my authority as captain to ensure the proper load of fuel was on board prior to departure. The secondary causes of the event was the lack of support I received from both my first officer; dispatcher and her manager. The lack of support made me question my stance and made me take steps I would not take again.when the PIC calls dispatch with a concern; especially over fuel; I would hope the dispatcher in the future would be more willing to help investigate the abnormality instead of saying the FMS is inaccurate. We are a team both with the goal of completing our flights safely. When one team member is concerned the other must listen and attempt to resolve any and all concerns. I raised a red flag on this release; I signed the release and accepted the flight knowing the odds of going to the alternate were close to 0. Sure enough; half way to ZZZ; the weather turned VFR and we even performed a visual approach. In addition; the dispatch team should review their release just as thoroughly as I do in the cockpit. It appears at times that the flight crew (and at times only the captain) are/is the only people/person to check the release in all of its detail. In this incident; I caught the error but had no support to figure out the error.in the future I will delay the flight until my concerns are resolved. There were a number of ways this could have ended differently. I take it upon myself to make a stronger decision next time this or similar events come up.

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Original NASA ASRS Text

Title: CRJ-200 Captain reported a large discrepancy between the expected fuel burn stated on the flight release and the actual fuel burn given by the FMS.

Narrative: While verifying the FMS was programmed correctly I noticed a large variation in expected fuel burn (from the release) and actual fuel burn (on the FMS). The following is a breakdown of the fuel comparison between the release and the FMS.In addition; the estimated extra fuel on board after burn off to ZZZ and the alternate ZZZ1 would had only been 170 lbs. According to the release; I should have had at least: 1034 lbs. This is a difference of 864 lbs between the extra fuel calculated on the FMS and the extra the release calculated.After realizing the discrepancy I called our Dispatcher. I informed her that I would like to add 500 lbs of fuel (following procedures set forth in the FOM) as the FMS was calculating the fuel numbers listed above and as seen on the screen shot labeled FMS Pre-Takeoff. It took a little more explaining but I was told that I had enough fuel to make the trip to ZZZ. I informed her that I would not have enough fuel to get to ZZZ1. The 170 lbs of extra fuel mentioned above did not include engine start and taxi which was estimated at 285 lbs as seen on the release. Again; she; perhaps confused; still said that I had enough fuel and was not authorized to add fuel.After insisting some more; she took the matter to her Supervisor whom stood by our Dispatchers decision to deny the additional fuel. Both our Dispatcher and the Manager indicated that my FMS must be producing an error and that they would be unable to approve the additional fuel. With the weather in ZZZ improving and looking as if IMC conditions were about to be lifted soon; I decided that the odds of going to the alternate were slim and elected to depart.After landing in ZZZ; I recorded a landing fuel load of 2;800 lbs which was almost exactly what the FMS originally estimated prior to take off. Which meant the estimate on the release was actually off by 671 lbs. I called our Dispatcher to inform her of the actual landing fuel as soon as we got to the gate.After further review with our Assistant Chief Pilot; we noticed that the extended flight plan portion of the release showed the fuel calculations ended at ZZZZZ intersection. The total distance not accounted for on the ZZZZZ1 2 arrival is 46 nm. From the furthest point on the approach (which we were vectored to): Total Distance not accounted for: 70.5 nm (46 nm + 5 nm + 19.5 nm)Subtract the distance from ZZZZZ to ZZZ (via direct as planned on the release) 26.5 nm. * This number was accounted for on the release and therefore should be subtracted from the total distance not accounted for. Additional distance flown vs planned: 44 nm.At an average speed of 200 kts. (usually 210 kts from ZZZZZ to final intercept followed by a speed reduction to 180 kts to ZZZZZ2 once on final) it would take approximately 14.5 minutes to fly the 44 nm at an estimated 2;600 lbs/hr (43 lbs./min *14.5 minutes) = 623 lbs. This is almost exactly the original difference I described above. The very next flight into ZZZ we noticed that the extended legs section of the release had the full arrival and the actual fuel burn was almost exactly as planned.The primary cause of the event was me not exercising my authority as Captain to ensure the proper load of fuel was on board prior to departure. The secondary causes of the event was the lack of support I received from both my First Officer; Dispatcher and her manager. The lack of support made me question my stance and made me take steps I would not take again.When the PIC calls Dispatch with a concern; especially over fuel; I would hope the Dispatcher in the future would be more willing to help investigate the abnormality instead of saying the FMS is inaccurate. We are a team both with the goal of completing our flights safely. When one team member is concerned the other must listen and attempt to resolve any and all concerns. I raised a red flag on this release; I signed the release and accepted the flight knowing the odds of going to the alternate were close to 0. Sure enough; half way to ZZZ; the weather turned VFR and we even performed a visual approach. In addition; the Dispatch team should review their release just as thoroughly as I do in the cockpit. It appears at times that the flight crew (and at times only the Captain) are/is the only people/person to check the release in all of its detail. In this incident; I caught the error but had no support to figure out the error.In the future I will delay the flight until my concerns are resolved. There were a number of ways this could have ended differently. I take it upon myself to make a stronger decision next time this or similar events come up.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.