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I havve tried to figure out how large my fuel tank is! I filled it to determine my miles per gallon and then refilled it. I put eleven gallons in, with more than 3/4 of the fuel tank showing. This would be about an 80 gallon fuel tank! I simply cannot believe it. What sizes were avaailble for 1991 GMC /Chevy 2500 PU? Thanks. -MIKEM

do you have dual tanks with a selecter switch

on the early diesesl liek my 85 long bed it has a 20 gallon tank the short beds had a 16 gallon tank fairly small considering the milage that the gas trucks got can you imagine a short bed 454 truck youd get aroud the block and youd be outa gas again

I wonder as well. when the fuel gauge reads empty I can consistently put in 70 L (a little less than 20 gallons) when I looked at the owners manual however it said that a long box had a 100L tank and a short box a 80L tank. is my gauge wrong and reading empty when ther's still 30L left or did one of the PO's replace the tank with one from a short bed? The tank looks like all the other tanks frtom long boxs I've had.

Andrew, just a single tank. 54 inches long and 14 inches wide! Must be 40 gal or more. Anyone know what sizes were available in 1991? Thanks.

1991 GM CK PICKUP SERVICE MANUAL specifies fuel capacity for gas or diesel tanks:

with short bed, 26 gallons (98 Liters)

with Long Bed, 34 gallons (128 Liters)

The only halfway accurate way to estimate fuel millage is to fill your tank full of fuel. Write down your mileage and drive. After your trip fill your tank to the same filled level as when you started. You can use several tank fulls if you want (greater accuracy). Write down your current mileage. Subtract your starting mileage from the end mileage. Divide the mileage driven by the total gallons used. This is your trip miles per gallon. Forget about using your fuel gauge as its' accuracy stinks.

while i agree that that is the only way to measure mileage it does leave some room for error espescially with diesel since it foams up so much while filling that it makes the nozzle shut off when not even close to full. gauges are very innacurate tho , that's why I wonder if I still have 30L left when the gauge reads empty. Also I can put in 20L and the gauge reads 1/2 full, another 20Land the gauge reads full yet I can put in a further 30L before it is truly full. My gauge isn't accurate but it is consistent

Consider the design philosophy of the fuel gauge by the manufacturer. Cost is probably #1 on the list. Reliability is next. The owner is not going to complain about having 30 L (4 1/2 gal) left in the tank when the gauge reads empty, but if the vehicle runs out just as the gauge reads E (or just before) and all hell breaks out at the dealership. Also, no one is going to complain if he has to put an extra 20 L (5gal) in the tank after the gauge reads full. Fuel tanks have a flat bottom so it is hard to get all of the fuel out of the tank (could be 8-16 L, (2-4 gal).

Fuel filler nozzles are designed to foam and shut off BEFORE the tank is completely filled to prevent spilling and atmospheric contamination.

I have a Little book that I write down the date, millage,and amount of fuel I put in the tank at each filling. This allows me to calculate my millage for the last trip or for the last 1000 miles.

I just thought that someone had an owners manual and knew the available sizes for fuel tanks, in 1991! Thanks guys. By the way JMAY, we should get in touch as I am in Mesa also! -MIKEM

Sizes Jmay stated are correct... and you probably have a long bed too. The fuel gauge takes a long time to come off of 'full', a slow trip to 3/4, a slightly faster trip to 1/2 and then I fill it with about 20 gallons. If I let the gauge get too much below 1/2, "I get a baaad feelin' in the pit 'o me wallet."