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I thought the 'Advertised Capacity' of our fuel tank was 12.4 gal as that is the number you see in the literature and in the owner's manual. But it seems that 12.4 gal is the USABLE CAPACITY and there is a non specified amount of EMPTY RESERVE, and the USABLE CAPACITY + EMPTY RESERVE = ADVERTISED CAPACITY. I found this piece of info on page 139 of the 2015 Owners manual:


"Empty reserve is the amount of fuel
remaining in the tank after the fuel gauge
indicates empty. Do not rely on this fuel for
driving. The usable capacity of the fuel
tank is the amount of fuel that can be put
into the tank after the gauge indicates
empty. The advertised capacity is the total
fuel tank size – it is the combined usable
capacity plus the empty reserve."


The reason this came of interest is I was out today for a spirited ride in the Central Texas Hill Country and I took some new roads and ended up further out on I-10 than I usually do. I checked the 'fuel remaining' and it said 60 miles and I figured I could head east towards San Antonio and fill up closer to home. I got on I-10 and the speed limit is 80 mph so I set the cruise control at 82 mph and sail along. The pavement is smooth and I was surprised at how quiet the cabin was at that speed. Eventually I see the mileage sign to where I was heading and it said 55 miles. I look down at the gauge and it shows 55 miles left in the tank...it's going to be tight. But at 80 mph it is sucking down fuel and in a few miles I realize it is going to hit zero before I get to the fuel station. The low fuel light eventually comes on and the needle bottoms out, still sailing along at 80 mph. The remaining mileage hits zero at 341 mi on the trip odometer, yet I'm about 7 miles from the exit. I slow down to 70 mph to save gas and made it to the Exxon station at the 348 mi mark on the tank. I fill up with 93 octane and the tank took 12.981 gals, 0.6 gal more than the 12.4 gal shown in the owner's manual. So the tank holds at least 13 gal of fuel, probably a bit more. I suspect the tank is 13.4 gal which includes 12.4 gal of Usable Capacity and 1 gal of Empty Reserve.
 

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This is interesting. Would it play a factor in e30 set ups?

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I thought the 'Advertised Capacity' of our fuel tank was 12.4 gal as that is the number you see in the literature and in the owner's manual. But it seems that 12.4 gal is the USABLE CAPACITY and there is a non specified amount of EMPTY RESERVE, and the USABLE CAPACITY + EMPTY RESERVE = ADVERTISED CAPACITY. I found this piece of info on page 139 of the 2015 Owners manual:


"Empty reserve is the amount of fuel
remaining in the tank after the fuel gauge
indicates empty. Do not rely on this fuel for
driving. The usable capacity of the fuel
tank is the amount of fuel that can be put
into the tank after the gauge indicates
empty. The advertised capacity is the total
fuel tank size – it is the combined usable
capacity plus the empty reserve."


The reason this came of interest is I was out today for a spirited ride in the Central Texas Hill Country and I took some new roads and ended up further out on I-10 than I usually do. I checked the 'fuel remaining' and it said 60 miles and I figured I could head east towards San Antonio and fill up closer to home. I got on I-10 and the speed limit is 80 mph so I set the cruise control at 82 mph and sail along. The pavement is smooth and I was surprised at how quiet the cabin was at that speed. Eventually I see the mileage sign to where I was heading and it said 55 miles. I look down at the gauge and it shows 55 miles left in the tank...it's going to be tight. But at 80 mph it is sucking down fuel and in a few miles I realize it is going to hit zero before I get to the fuel station. The low fuel light eventually comes on and the needle bottoms out, still sailing along at 80 mph. The remaining mileage hits zero at 341 mi on the trip odometer, yet I'm about 7 miles from the exit. I slow down to 70 mph to save gas and made it to the Exxon station at the 348 mi mark on the tank. I fill up with 93 octane and the tank took 12.981 gals, 0.6 gal more than the 12.4 gal shown in the owner's manual. So the tank holds at least 13 gal of fuel, probably a bit more. I suspect the tank is 13.4 gal which includes 12.4 gal of Usable Capacity and 1 gal of Empty Reserve.
This is interesting as I've very rarely ever put more than 10 to 10.5 gallons in even when I get down to the low fuel light. I think there was a TSB that you could have the PCM flashed to make the readings more accurate. If you got down that low, I'm assuming yours is newer or had the update?
 

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Very interest, at first I was expecting to hear they played tomfoolery where they advertise 12.4, but really only 11.4 is real-life usable. That is how your first paragraph interpreted to me. But good news you payed attention the measurement going in and that is not the case.

But as commonly recommended I fill up at 1 quarter left, so I really am only getting around 10-11 useable capacity. Personally this is my first small gas tank ever and I do not like it. I love the ST, but if I was forced to make a list of the less than perfects.

On a side note, my car salesman "sweetened" the purchase a bit by offering a full tank of gas. Little did I know, that tank cost him $20. Not mad, in fact thats a pretty gentle way to get ****ed.
 

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This makes a lot of sense. I have seen similar behavior on Top Gear where they do fuel challenges. They often show no miles left and still travel many miles afterwords.

The "miles remaining" screen on the trip computer is a very conservative estimate. No car manufacturer wants to be informed that someone is on the side of the road with an empty tank with 10 miles remaining on the display.

So as long as you have a positive on your miles remaining, you should be safe.

However, for me, I start looking for gas station when the remaining miles dips below 100 to empty and I don't ever like it getting below 50.
 

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Very interest, at first I was expecting to hear they played tomfoolery where they advertise 12.4, but really only 11.4 is real-life usable. That is how your first paragraph interpreted to me. But good news you payed attention the measurement going in and that is not the case.

But as commonly recommended I fill up at 1 quarter left, so I really am only getting around 10-11 useable capacity. Personally this is my first small gas tank ever and I do not like it. I love the ST, but if I was forced to make a list of the less than perfects.

On a side note, my car salesman "sweetened" the purchase a bit by offering a full tank of gas. Little did I know, that tank cost him $20. Not mad, in fact thats a pretty gentle way to get ****ed.
Better than when I bought my truck and they "filled the tank" and when I drove away it read just under 3/4 tank. I went back and asked about it and they said "oh we can only put up to 20 gallons in" lol.
 

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I was stoked when I left the dealer in my truck with a full tank. (36 gallons). I would sometimes have to charge the card twice when a fill up stops at $100.

The ST does drive me crazy for the tiny tank. Isn't it bad to run down to the low fuel light in our cars or is that just spirited auto X style driving?


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