You're forgetting the reserve. Your ~13 gallon tank has approximately 12.5 gallons of usable fuel in it when full (the last half gallon is not accessible). The light comes on when you have approximately 2.4 gallons reserve left, or when it has used about 10.1 gallons. That would put you in the vicinity of 25 miles per gallon (24.75 if you want to get picky).

At that rate of burn you could go another 60 miles or so after the light comes on before you actually run the fuel pump dry. If you run Torque as an engine monitor, you can actually monitor the remaining fuel in gallons (or liters) so that you know when you're really getting desperate.

New math I guess?

Not sure if trolling but I'll give it a try...

If you were to get 10 mpg for example, and you drove 1100 miles per month, you would need 110 gallons per month (1100/10=110) Depending on the size of the gas tank, here are the ways you could do it:

11 fill-ups at 10 gallons each = 110 gallons.
10 fill-ups 11 gallons each = 110 gallons.
Now you try:
??? fill-ups at 55 gallons each = 110 gallons.

Unless price varies drastically during the month in a predictable way, and you can alter your gas tank size to need to fill up ONLY when prices are low (this doesn't happen), then you will pay the same amount per month regardless of how many times you fill up.

The only real way to reduce your fueling cost is to use less fuel by either reducing milage, or increasing mpg. Not going to get into how that may affect global economics but you get the picture.

Also, an extra gallon is not going to cut the amount of times you fill your tank in half...

This math that OP is using hurts my head. Assuming gas prices stay on par, you arent saving any money at all. Less trips to the gas station, but thats it. Why did you even get a BRZ if you wanted a fuel efficient car.

That's because it's not math.

Honestly, I'd like a bit bigger tank myself. My fuel mileage sucks in the winter.

Also, when I do roadtrips home, it's about 660km. I get about 630km to a tank when making that trip.

And stopping for gas is a major inconvenience? A bigger tank just means you would go even further before filling but it would still need to be filled.

You guys would have shit with some of my old cars that had to be filled up two or three times a week.

Nah, more like just a little OCD on my part. On the original Primacies I could *just* make that trip.

I still struggle with the fuel mileage drop with a cold engine on the BRZ. I've never heard of any other car being this affected. I easily take a 20% fuel mileage hit when temperatures drop. Only affects short run city driving. If I do a long highway trip it's still reasonable.

I go from my normal average of 6.9L/100K in summer to 7.1 in the winter. That is 99.5% highway though.

Normally I'm 6.6 highway, winter or summer.

Short run city driving in the summer is about 9L/100km for me. In winter that jumps to 11L/100km, not counting extra idling for shoveling out/defrosting.

Moved to a new apartment last year with indoor heated parking, saw a 1L/100km improvement by having a warm engine in the morning.

Its possible the drop may have something to do with the winter blend of fuel offered in your area? Ive never heard of major drop in fuel mileage in most cars for different seasons.

Winter mileage difference may be related to:

1. My ltft goes from -3 in the summer to +4 in the winter. While that by itself would not necessarily cause this effect, it shows that the there is some calibration in the ECU that may be off. I am running oft stage1, but I dont think they messed with the ambient temperature calibration.

2. Oil temperatures are about 30 degrees lower in the winter, making it slightly thicker.

3. Colder air is more dense, meaning you have to push greater mass out of the way at speed.

4. Tires don't have a chance to get as much heat in the winter as summer, so the air inside doesn't expand as much, causing running tire pressures to be lower.

5. Freezemiester hates us.

I've read a lot of really stupid things on this forum, but this may win.

6. Fuel mixtures in the winter are slightly different (not sure if better or worse for mileage but probably worse)

7. Denser air means you can burn more fuel which means more hp / less mileage if press the gas as hard as you normally do.

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