Actual Capacity of K/5 Belly Tank?

['68OrangeSunshine]

Anyone know the actual capacity of the stock gas tank in a '71 GMC Jimmy?
Owners' Manual states a nominal 20.5 US Gallons.
Last Weds evening, I ran out of gas.
[My fuel gauge doesn't function. I know the gauge itself is good, so it must be in the sender. The belly tank is protected by a huge skid plate held on by about 48 capscrews, with the authority of 52 years of rust-in-place. I usually use a log. But it's not infallable].
Roadside Rescue dispatched a driver, who told me he needed a dollar amount, for the gas, so I said get me $20 worth. At $3.599 that should have bought 5.55 gallons. He showed up with a plastic 5 gallon gas jug and funneled it into my tank. I gave him a Twenty. Truck started and I got to my meeting, 45 minutes late.
After the meeting, [about 3 - 5 miles later] I stopped at a station and pumped gas until it shut off from filling. I did not overfill or spill. Gas Pump registered 19.5 gallons.
So the math is off. I know I did not burn 4.5 gallons in 5 miles. 5+ 19.5= 24.5, which is beyond the capacity of the Blazer tank. What happenned to 4 gallons?

[1970cstblazer]

At least in 1970, the capacity was advertised as 23.5 US gallons. Pretty sure it's the same 1969-72.

[Getter-Done]

The information I found was 23.5 gallons also.

And also: Was that 5 Gallon Gas Jug Full ???

Year:: 1970
Base Price: 2,955 (6 cid.) 3,050 (8 cid.)
Wheel Base: 104 in.
Length: 177.5 in.
Std. Engine, (net HP):
OHV Six-cylinder 250 cid. (110) @ 4000 rpm
Rear Axle:
GM Corporate 12-bolt (8.7/8-in. 1.31 Axle Dia. 30 Spline)
Transmission (M):
SM318/SM326/SM330/T-89A/T-150 3 spd. (2.47-3.50:1 First Gear)
SM465 4 spd. (6.55:1 First Gear)
Transfer Case (M):
NP205 (1.96:1 Low Range)
Dana 20 (2.03:1 Low Range)
Production Total: 11,527
Weight: 3,677 (6 cid.) 3,807 (8 cid.)

Fuel Tank Capacity: 23.5-gallon

Height: 68.7 in.
Opt. Engine, (net HP):
OHV Six-cylinder 292 cid. (125) @ 3600 rpm
OHV Eight-cylinder 307 cid. (135) @ 4000 rpm
OHV Eight-cylinder 350 cid. (170) @ 3600 rpm
Front Axle:
Dana 44 (8.5-in. 1.31 Axle Dia. 30 Spline)
Transmission (A):
TH350 (2.52:1 First Gear)
Transfer Case (A):
NP205 (1.96:1 Low Range)
Notes:
New grill with six groups of silver "dashes" above and below the horizontal aluminum center bar with Chevy's name across it.

The Blazer's single-unit body was joined to a heavy channel steel frame and had a completely removable fiberglass top.

A 4x2 Blazer was produced this year, but less than 1,000 were made.

['68OrangeSunshine]

OK. 23.5 gallons. That is a big difference of three gallons more.
The gas jug the guy had was a Wedco, not the Blitz style copy of the US GI can or the WWII German-inspired NATO 20L jerry can.
I've had a few, and it looked pretty full. Not sure if he had the proper caps on both ends, so some may have sloshed out on the way.
I guess it was close enough for gov't work, so I didn't get boned,,, Much. For an emergency I did OK.
Thanks, guys. I was under the impression the Blazer belly tank held less than the Behind-the-Seat tank. I've crammed 22.5 into the one in my '68 C/10 Stepside, although the manual states 20 gallons.

Also I've never seen a Factory-optioned [RPO L25] 292 L6 in a Blazer/Jimmy. I see it was an option, but apparently a very rare one.

['68OrangeSunshine]

Funny, though. LMC Catalog lists the Blazer/Suburban tank as 21 Gallons.
Conversion belly tanks for under pickups are 17 Gallons.
And Truck and Car Shop calls theirs a 20 Gallon tank...
Pretty sure mine's an original.

[Getter-Done]

I noticed that Some of the vendors, when searching for capacity,
Was different.

I had a 76 Blazer that had a 31-gallon tank.

This is what sparked my curiosity.

The only true way too tell what yours holds (you Know),
Run it out of gas and have a (measured amount to add back).