So I found my self pumping $4/gal. today(SoCal), last week it was $3.91! I have a '00 gt (5spd) and my questions are:

1) Since it says "premium unleaded fuel only" on the gas cap, i'm sure there are exceptions where I can pump regular(89) when I am really down to my last dollar. Any GT owners want to share their input? (I've read that using premium all the time can be bad for the engine, but I'm assuming it's "required" for the GT(don't have the manual) and I should be ok using premium regularly).

2) I have been reading past posts, and I am going to use the trip odometer to calculate how many miles it drives with a full tank. I want to make sure I'm getting every MPG the car can get. But I have never let my fuel gauge pointer(on this and previous cars) reach the "empty" point, which brings me to the next question, how many miles/gallons are left in the reserve tank?

 

you could always mix octane booster stuff with your gas if you want to buy cheaper gas. or you can bite your lower lip like i do and just buy premium.

 

I only have a GS auto but the best I get is 275 miles to the tank.

 

I believe that if you use lower octane fuels in the v6 your engine can sense it (knock sensor maybe?). When it does it switches to a different performance map for air/fuel/timing so your engine goes to limp mode and you lose performance.
My mileage varies hugely on how and what type of driving it is. Around town I usually get about 350 km's per tank but I can get over 500 on long highway trips. I think there is arounf 15 litres left in the tank when the light comes on. I have made it 43 km's on the highway after the light came on but I didn't push it any further I got chicken>

 

i'll stick with premium, i don't want to add anything that will have costly consequences. So i have about 3+ gallons left in the reserve tank(assuming my math is right, 1 gallon= 3.7?? L), nice.

 

The way I ws told to check for sure was drive until the light comes on then immediatley go and fill up. Then subtract how many litres or gallons you in from the tank size. This will at least tell you how much is left in the tank when the light comes on. Then subtract 1 or 2 because I'm pretty sure you can't get everything out of the tankn and that will give a rough number for what's available to you when the light comes on.
I always meant to do it, but frankly, gas is about $1.28 per litre here which makes it about 60 to 70 dollars to fill and I don't have it most of the time so I just do 30 to 40 dollars worth.