Royal Purple treatment with inconsistent results

[Brandon Gatz]

My 95 F150 5.8L has always netted me about 9mpg in the 5 years I've owned her. Threw in a can of RP fuel treatment last week and that jumped to 11mpg for that tank of gas that lasted 200mi instead of 170ish. So impressed was I that I treated the next tank of gas with another can of RP, but strangely, I am back to my 9mpg/170 range for that tank every subsequent tank since. Driving patterns and weather conditions were no different on the initial treatment.

 

[SubieRubyRoo]

Save your money. It was something other than the fuel additive. Maybe a fuel pump that got more in the tank before shutting off.

 

[danez_yoda]

A little math.

170 miles at 9mpg is about 18.5 gallons of gas
170 miles ar 11mpg is about 15.5 gallons of gas.

Net saving is 3 gallons. $2.50 / gallon is $7.50 saved.

Royal purple magic mix to get that savings... ~$12.......

.

Still lost money even if it did work to gain 2mpg

 

[Linctex]

Check your tires pressures - inflate to max allowable for best mileage.

 

[Chris142]

That mpg is real bad. Have you replaced 02 sensors and coolant temp sensor?