Though propane has and octane rating of 110, it also has an energy density that is 73% that of gasoline--I.e. it will take 1.37 as many gallons of propane to get the power of 1 gallon of gasoline (this is oversimplified, however the numbers are close enough). This pretty much negates any cost savings.
Also, in real world applications the advantages of the higher octane are not practically achieved. Simple propane conversions of gasoline engines usually produce 80 to 85% of the power that can be realised with gasoline--this is why you do not see propane powered race cars--just fork trucks, taxi cabs, and other fleet/special use vehicles...
- 2003 GT, UPR X, FRPP 24lb/h, Magnaflow, PP 70mm TB & plenum, Delta Force tuned,
Steeda UDPs, Ralco flywheel, RAM HDX clutch, 3.73s, 262 rwHP/305 lb-ft.
New ride (7/1/2013) 1998 Mercedes SL500-5.0L 32V VVT 326/347 HP/tq