Y'all realize gas hasn't increased in price - adjusted for inflation - in over 40 yrs, right? Gas follows inflation and, other than a few blips (some big), gas is effectively always $4.20/gal.
How can there be gas specific inflation. Do you have special dollars that can only buy gas?^that^ is a general CPI calculator. Gas-specific studies/reports vary a bit - from $3.60-4.10 but the basic premise is the same... gas is always around $4/gal adjusted