Last week my brother and I went up to my cabin to get it ready for winter.
We went into town to get some things and stopped at a filling station. I fueled his truck (2017 Chevy Colorado) while he went inside to pay for the gas and buy us some beer and snacks.
Here is the thing: his truck took over 26 gallons. I knew we were running on fumes but I don’t see how I got 26.4 gallons into a 21 gallon tank.
He looked at both his owners manual and his window sticker and both say the truck has a 21 gallon fuel capacity.
A few days later when we got back home to the south eastern part of the state we had to refuel again. 25.7 gallons. WTH?
I know some manufacturers put slightly bigger tanks than they say and have gas gauges read less than the tank has to keep people from running out of gas on the highway. But no way would they put a tank 6 gallons more than the manual says.
Poking around online, you’re not the first person to notice this. Some folks definitely seem to have 21 gallon tanks (typically refilling at about 19 gallons) and some folks have regularly been able to put 23 or 24 gallons into their supposed 21 gallon tanks. It’s not consistent.
A theory that I found on one message board is that GM put Silverado tanks (26 gallons) into some Colorados, but this isn’t confirmed anywhere. Maybe they had a temporary tank shortage during production, or maybe they somehow ended up with too many 26 gallon tanks and decided to use them up elsewhere?
Does your brother have the tow package installed? Maybe they put bigger tanks in for that.
I wasn’t able to find anything definitive, but I can at least confirm that you aren’t the only one to experience this.
This is just an anecdote, so might not help your exact case. Years ago I owned an early 90s Buick Century. The owner’s manual listed the tank as 12 gallons or so. If I ran it down to E, I could easily put in 12.5-13.5 gallons. I’d blacklisted half the gas stations in town as having fraudulent pumps, until I got a copy of the shop manual which described the car as having a 14 gallon tank. That made way more sense than that all of the gas stations were ripping people off, and I was the only one who had noticed.
So that it is one example, and not third hand, or I read some place, but that I actually experienced of GM being inaccurate in an owner’s manual about the size of the gas tank. Though, I would not be surprised if it read “12 gallons plus a small reserve” or something, but that’s not how I remember it.
I have a Silverado (my son was using it to move some stuff into a rental investment property he bought) which is why we were using Pauls truck instead of mine and why the entire thing even came up.
“Hey, this thing has the same size tank as my truck, 26 gallons”.
“Whatta you talking about. This has a 21 gallon tank” “Well I just filled over 26 gallons into it”
(pulls out window sticker and manual out of of glove box) “21 gallons!”
“That pump musta been off. We just got fucked at the service station, Sammy Boy!” ( one of my nick names).
But then when we filled up again he realized he had the bigger tank. Those were the only 2 times he had ever ran the tank below half (yeah, he’s one of “those guys” :rolleyes: ).
My 87 Suburban had the opposite configuration. The thing was sold with the optional 32 gallon tank. All was fine until one night when I was calculating if I could make it home. Quarter tank of gas, 13 mpg, 60 miles to go. Easy. Turns out the truck has a 26 gallon tank, and when the gauge says quarter tank it actually means a little less than an eighth of a tank. Your brother won the same gas tank lottery that I lost.
Unlike passenger cars, pickups tend to have more room and options to put bigger gas tanks in them. I suspect like others, Cheverolet for whatever reasons found it more feasible to just use their Silverado and GMC Sierra 26 gallon tanks, although they must have decided this after their marketing and sales teams were made aware of it, otherwise, they would have been happy to let their customers know of the bigger tank and longer range.
If the gas tank supplier had a problem with the welds on the gas tanks it produced at a particular plant on a particular date, the vehicle manufacturer needs to know which cars or trucks received those tanks, so they know which vehicles need to be recalled. So for that reason, they don’t just change a part willy-nilly but instead track everything very carefully. So GM should certainly know which fuel tank your truck received and what its capacity is.
I bought a 1985 Chevy Silverado PU new off of the lot. I had the dealer install an auxillery tank on it, a second whole tank. So there’s more room there than you think there is.
In Missouri, gas station pumps are certified yearly by the state for accuracy, and an official sticker is placed on the pump to show this. I expect every state has a similar program. Can you imagine the howls and outrage if every customer at the stations mentioned were charged for 25% more gas than the pump delivered? That simply would not fly.
For decades vehicle fuel tank capacity specs have been approximations, not precise measurements. I find it quite plausible that in a handful of situations the specs could be significantly wrong. I find it implausible that gas stations have pumps that are inaccurate beyond some negligible amount, and totally ridiculously implausible that they’re off by such a large degree.
So what’s your thought then? All the specs say his truck has a 21 gallon tank but twice in a row I filled over 26 gallons.