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Fuel Tank Capacity


Well-known member
Dec 5, 2001
Cross Roads, Texas, U.S.
'89 dk red coupe
I just looked through the new specifications page - loved it, BTW - and I had a question about the stated fuel tank capacity of "20 gallons" for an '89. I'm under the impression that earlier versions of the C4 had a 20 gallon tank, but that by '89 modifications had been made to reduce the capacity.
I know that, having run mine completely dry, it doesn't hold more than 18.5 gallons or so unless you fill the filler neck.
Comments? Anyone have other information? Is mine defective?
Does someone know what I could do to get the full 20.0 gallon capacity in an '89?
don't know about the '89, but I ran my '93 completely out and it took 20 to fill. So I guess if they did make a change, they must have changed it back.
I've never completely run out on my '95, but I have put over 19 gallons in when it was really low. Its a coupe with auto if that might make a difference.
The lowest Ive got

(Besides driving a FIAT in high school)

Was 19.1 gal in my 88 convertable

The pump was cavatating (sp?) on the way in!
the gas gauge showed 1 bar left.

I guess it has to do with the pickup placement..

I'll bet a DRY tank will hold 20...

Redbob said:
...it doesn't hold more than 18.5 gallons or so unless you fill the filler neck.

One thing to keep in mind when running your tank low on fuel is the fact that the cooling effect the pump receives from the liquid (gasoline) is significantly dimminished, and therefore the life of the pump will be shortened if allowed to run in this condition too long.

Another important thing here is when you are filling the tank. Never fill the tank to the top of the filler neck, what was once known as "topping-it-off" can allow liquid gasoline to enter the vent line and it could be possible to get gasoline all the way back to the vapor cannister. :nono I always pull it out when it shuts off at the first sign of liquid. ;)

_ken :w
I have run out a few times on my '88 coupe.
I can never get more than 18.5 gallons in it.
I've run mine out once, just to see how low it would go. Hint: When it says reserve--go get some gas. I was less than a mile from the station and I was sure I got 21mpg. I only get 20. OH--it did take 20 gallons.
I do know that mine ('88 with 20 gal tank) has an air pocket at the top of the tank to allow for expansion when fuel gets hot. The sceniro that's dangerous is just after you filled it and parked it on a hot day. That's why GM (all others) have done this
The depth of the intlet into the tank determines the pocket size.

I have babied it to get the 18.5. The level kept dropping as the air in the pocket escaped.

I am thinking perhaps the '84 has a replacement tank (non GM) or very little or perhaps no air pocket in that year.

On my New Beetle Diesel it has a plastic tab that gets depressed when the cap is tighten down, Pressing that tab manually allows air in the pocket to escape. I do it with the nozzle tip every time I fill the tank (750-800 miles). It gets an extra 2 gallons in the tank. The average is 14.5 gallons by venting and 12.5 no venting. This tab is handy and almost all the folks on the VW TDi list vent theirs when filling it up.
Fuel capacity


My first trip out of my drive way, I ran out of gas on the way to the gas station. I filled it completely and only put in 18.5 gallons.

I had the same questions after reading about the 20 gal capacity.

Let's hear a round of applause for those of us who have never run out of fuel. Sometime you will have to tell me how you let that happen (unless your gas guage is broken).

When I was a kiddie bouncing on my daddy's knee, I was told if you let your tank get close to empty, all the crap in the bottom would be forced through the engine. I believed it and never let it get past a quarter tank. Anal? Maybe, but you won't find me standing roadside with a gas can in my hand! :s
Little Miss Perfect

Not all of us have that much common sence. :p
There are a few reasons to run out of gas:
1) I just like paying over $20 for a fillup
2) When I first got the car I wanted to see just how far you could go on one bar (not that far as it turned out :))
(I've run out with other vehicles too trying to find out what was below that big E)
3) I forgot (My favorite)
4) Cultural experiment. You meet some fine human beings while thumbing to the next exit.

Ya know, you have a fuel filter that is supposed to pick up all that stuff in the bottom of your tank.
I make so many other dumb mistakes I just had to capitalize on the one that I haven't made - yet. As a matter of fact, my mechanic just gave me a safety tip on how to wedge a screw driver in the hood support bar (non-technical name) so that it doesn't accidentally come down on me.......again.

But I liked your reasons. :beer
Hood supports!

Breakdown and buy new hood supports....

I got all 3 of mine for 150 (ish)

28 for the small ones
85 for the big one

After market ( Not factory )

Now the hood opens like a dream AND STAYS UP!
no screwdriver needed....

I got bonked ONCE and that was enough for me!

Not to mention if the hood SLAMMED down all the damage it would cause.

There is a trick installing all 3 at once. Let me know if your going to do it.

Oddly, Mike, they all still work. I just didn't notice the main support wasn't quite hooked and jostled the hood while replacing the air filter. It came down gently giving me an opportunity to ease it down with my right arm. Which now is extremly black and blue.

The next big expense is tires and I was surprised to see that Bridgestone's at $160 and Firehawk's at $208 are favored over the stock Goodyear's at $197. I will go stock as I happen to have a new one stored away but was curious as to why it ranked third amongst Corvette owners. Any thoughts? :confused
Even the goodyear dealer...

My local goodyear dealer wouldn't even sell me a goodyear tire when I went to him for new front tires. He said that they weren't worth the price and he got me some Kellys (Defender ZRX+4--yeah, I don't know what that means either). I like them. P255ZR5016s for $150 each, mounted & balanced.
Interesting. I just put a set of off brand Kelly's on my El Camino for low bucks and a pretty good ride. But the Goodyear's on the Vette are almost 7 years old and the only reason they really have to go is dry rot - my usual tire killer.
yeah, my old rear tires were goodyear and dry-rotting, which made them hard and unresponsive, but they did make some pretty blue smoke. :Roll I figured that since they were coming off anyway I might as well burn 'em off a bit. :upthumbs
Hey listen I don't want to ruin this guy's thread on gas tank capacity but at quick glance I though your pic of the '84 had you yanking the wheels. Is it an optical illusion or is there some weight distribution attributing to the incline? One too many Bacardi's on my part????:t
Tee many Martoonies?

Honest ossifer, I haven't dropped a drink all <hick> night. :drink
What can I say, my driveway is slanted and I took the pix without thinking. As someone here said, it looks like it wants to take off. I'll take another pix in the springtime after I get it repainted.

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