MPG....For what it's worth

Duc_Z09

Look, I drive for an average of maybe 50 miles on a new tank before those dash lights even start gong out. Sometimes the last one lights up when I fill up, sometimes it doesn't. And by the time those lights register that I have half a tank left, I'm always well beyond halfway to the 320 or so miles I usually get before my fuel warning starts kicking in; it's almost comical how quickly that last indicated "half tank" goes away. Those LEDs aren't even close to a linear representation of how much fuel you actually have and basing MPG off of them is a fool's game.

The bottom line is that there are only 2 times that you can be sure of exactly how much fuel is in your Z; when the pump stops you from overfilling and when you stall out from going too far between fill-ups. Everything in between is just a bad guess that I wouldn't put any confidence in whatsoever.

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2009 370z #206 (all mods are Home Depot)
2009 Ducati 848 (full Ohlins, Termignoni, etc)
2003 Grand Cherokee (long arms, big tires, 4.56, lockers)

Zipper 104

I mentioned the lights only in passing as reference. What the lights showed played no part whatsoever in what I did. I simply filled the tank up at the start of the run letting the nozzle click off a couple of times in an attempt to get as full a tank as I could. I did this on both ends of the 75 mile stretch. If there was a difference in the volume of fuel in the tank in the beginning versus the end, it would have been mere ounces.
That's the only real way to determine actual consumption. Gauge lights and in-car computer are simply fluff. Driving further into the tank would have been preferable for sure but I didn't and don't care. End of story.
I explained what I did to arrive at the numbers I got. They speak for themselves. Like it, or not. That's what they were. I had no hidden agenda.
We all know the 370 is no Toyota Prius, and nor do any of us care.
What I arrived at showed (to my satisfaction anyway) that if you keep your foot out of it, the car is capable of half decent fuel consumption numbers at 60 - 70 mph velocities out on a relatively flat freeway void of much congestion.

104

JARblue

I bet at 55 mph in 6th gear, downhill, with the wind at your back, and maybe a tune you could get 35+ mpg

I've gotten over 520 miles on one tank before. Filled up over 18 US Gal, which was over 29 mpg for the tank. And that was at 70 mph on cruise control most of the time.

I've gotten 112 miles on that first dot before - it's the best one!

No but seriously, the way the dots drop off slow at first and then rapidly as you approach empty is easily explained by the shape of the gas tank. The dot gauge is just a float in the tank estimating how high or low the fuel level is, and it doesn't take into account the shape of the tank. Since the tank is larger at the top than the bottom, the float does not drop at the same rate when the tank is full vs empty. I would never trust that gauge.

I could care less about my mpgs, but I religiously pay attention to the mileage I get per tank. Therefore, I know almost exactly how much fuel I have at any given time just based on the miles I have driven since last filling up. I hit the 50 miles left warning and know that most of the time I have at least 100-120 miles remaining of casual driving. I often fill up more than 18 US Gal. Driving habits alter mileage, of course, so I take that into consideration as well.

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Duc_Z09

Maybe I didn't understand your last post. When you mentioned that you were starting with 3/4 tank, I assumed you were basing this off of the gauge, which is very inaccurate.

+1. Exactly. I'm usually putting almost 18 gallons in every 320 miles or so. Maybe I should drive less "enthusiastically."

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2009 370z #206 (all mods are Home Depot)
2009 Ducati 848 (full Ohlins, Termignoni, etc)
2003 Grand Cherokee (long arms, big tires, 4.56, lockers)

JARblue

Absolutely not!

I may have one of the higher mile per tank numbers around, but I have a pretty low one as well. A couple of summers ago I took the Z around COTA for 6 laps at speed and ended up filling up that tank at 120 miles for an average of ~8 mpg.

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