We currently offer a massive range of downloads for FSX, as well as older flight simulator add-ons for the ever-popular FS2004, FS2002, CFS3 and now becoming ever popular with dediced virtual aviators is Laminar Research's X-Plane series.
The flight planner in FS is not all that great when it comes to estimating the fuel burn needed to make a trip, as it does not include taxi times apu fuel or any reserves at all. But 200 lbs is not a whole lot of fuel
you could use that just taxing from the ramp to the runway. Rember fuel weighs approx 6 lbs per gallon so 33 gallons is a drop in a bucket. Think a little like 2,000 lbs minimum a B737-engine will burn approx 400 to 500 gallons a hour PER ENGINE. REMBER this is not your family car that gets 20 miles to a gallon
Ask any pilot the only time they have to much fuel on board is if they crash. The NAVLOG also does not compensate for weather either, it just gives you the estimated burn for a clear skys trip, So if there is a headwind, forget the burn in NAVLOG. Go into Settings/realism/aircraft/engines & tick Unlimited Fuel & you might never be caught short!