Somewhat buff fuel consumption rate

The 27.8 fuel consumption rate is based around a single engine, but a significant number of players use 2 or 3 engines, which are much more difficult to use with this previous fuel rate. Decreasing the fuel rate to some degree helps account for this very common setup while still maintaining the intended effect on fuel balancing.

lua/acf/core/globals.lua

@@ -123,7 +123,7 @@ do -- ACF global vars
 
 	-- Fuel
 	ACF.RequireFuel        = true -- Whether or not fuel usage should be required for engines
-	ACF.FuelRate           = 27.8 -- Multiplier for fuel usage, 1.0 is approx real world
+	ACF.FuelRate           = 15 -- Multiplier for fuel usage, 1.0 is approx real world
 	ACF.FuelFactor         = 1 -- Multiplier for ACF.FuelRate
 	ACF.FuelMinSize        = 6 -- Defines the shortest possible length of fuel tanks for all their axises, in gmu
 	ACF.FuelMaxSize        = 96 -- Defines the highest possible length of fuel tanks for all their axises, in gmu