Quoting Chiltons? Please don't do that again or I will hurt you.
The std cab longbox had a 17gal, but there is ample room left ofer in the tank
to squeeze in an extra gallon or two of you are patient.
there's a difference between "rated capacity" and actual "total capacity"
The Main tank in my truck was at one point rated at 21.8gal but changes
in filler return hose length vent assembly spring tension (yada, yada, yada)
changed that capacity from anywhere from 70gal to 21.8 depending on which
exact owners manual you were reading the spec out of.... but from mid 1990 through atleast the end of '94 it's the same piece of plastic.
And I have personally squeezed 24.1 (measured with a 5gal pump certification can)
into that tank on more than one occasion (filled to standing fuel in the filler neck)
My REAR tank is "rated" for 18gallons, filled to the same standard (standing fuel in the filler neck) it holds 21.55gallons, my rear tank is NOT an RBV tank.
that all being said the early trucks came two ways, long box and short box.
the long box has always had a 17.0, the shrot box 15.something (varies)
but most often 15.2.
the supercab perversely originally came '86-88 with a 14.5gallon tank
Bigger heavier and gets less mileage and has the smallest tank...
way to go Ford! they corrected their mistake going into gen2 by
upping it to a 17gal plastic tank and again in mid '90 with the
21-something tank...
18gallons into a 17gallon tank? even if it's actual absolute capacity
with no vapor space was only 17gallons the filler hose will hold atleast
another gallon once full.
but all fuel tanks are designed with a certain ammount of vapor space because gasoline being a complex mixture of hydrocarbons doesn't have an even cofficient of expansion relative to temperature, so in some temperature ranges it expands like crazy if only warmed a few degrees... this is important because the tank MUST contain that
expansion, so the tank is typically 15% larger than it's rated capacity.
Heading out on a long road trip this fact can be useful...
Particularly if you do like I do... I buy as much gas as I can get from
the local junkyards that by law must drain it out of the incomming
junkers and don't want to pay hazmat disposal companies to haul it away....
Or build a legal storage facility to stockpile it....
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