The fuel consumption formulas used by the original HOST and DOS Planets/Winplan were not exactly known when PHost was initially written. PHost's formula therefore differs a little from HOST's. It is possible (though unlikely) that your client program may tell you that you only need a certain amount of fuel to get to your destination but in reality PHost may require more. HOST sometimes also requires more fuel than the client programs predict.
Some other reasons why a ship can use a different amount of fuel than predicted:
- Did you try to cloak? Cloaking also needs fuel.
- Are you using UseAccurateFuelModel? The "accurate" formula yields different results than the one implemented in DOS Planets and Winplan.
- Did you tow a ship which changed its mass? Ships may get heavier (Gather-type missions) or lighter (Alchemy, Mine laying).
- Did someone tow your ship? When you break out of a hostile tow, you'll be moving a different distance than predicted.
Modern client programs such as VPA or PCC aim for precise fuel computations and include support for PHost formulas and predictable events, but can of course not predict your enemies' actions.
See also HOST/PHost differences for a list of all known differences between HOST and PHost, as well as our statement why PHost stays different even though HOST formulas are now well-known.
