MPG....For what it's worth

Zipper 104

I know a lot of you don't give a rat's a** about gas mileage on your Zs, so this isn't for those of you.
I just made a return trip this weekend from Vancouver, B.C. to Renton, WA.
My Z turned 2000 miles on this trip. I figure it's safe to say my Z is broken in now.
I decided I wanted to see what kind of mileage I would see if I nursed it over a stretch of WA state I-5.
On the way home this a.m. I filled up just south of Everett, WA from near empty. (2 lights) I drove 122 kms (75.80 miles) to Ferndale, WA where I topped up the tank. It took 2.18 US gallons (1.81 gal Imperial) Gas gauge dropped no lights over this distance.
I will qualify that I only put my foot in it once. I kept to the speed limit the entire time (it varied between 60 and 70 mph over this stretch and I was always at the limit)
I'd say I held rpms to around 2200 thru 2500.
That worked out to 34.7 miles/US gallon (41.8 miles/Imperial gallon) provided I can trust the gas pump and the trip meter in my car.
Given the price of gas at Ferndale it worked out to roughly $0.10 (US) per mile, gas-wise. Gas got more expensive the further north I went.
I seem to recall I paid around $3.27 USD/gallon???? near Everett and $3.64 USD/gallon in Ferndale.

There were 6 radar traps between Renton and the Canadian border. 5 cars, one bike. (BMW) One radar trap on the Canadian side (car) between the border and Vancouver. Boy, some parts of I-5 and WA 405 are getting pretty ratty these days. And I thought our roads were crap.

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need4speed255

I don't think that is an accurate measure. You need to drive through a whole tank of fuel in order to get an accurate reading. Only driving through 2.xx gallons leaves a lot of room for error in order to fill up to the same level that you were previously at.

need4speed255

I am not too familiar yet with the information display to the left of the gauge cluster. Doesn't that display show average mpg? Not sure if you would have had to reset it before the test.

Duc_Z09

There's no way in hell you got 34+ mpg out of this car.

/thread.

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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

Another example then.....I drove my Z starting out with a full tank for several days around town and a few highway miles prior to starting the trip.
I left home with about 3/4 of a tank. I drove to Renton WA from Vancouver with NO nursing of the gas at all, although I don't abuse speed limits much.
I showed 2 lights on the gas gauge when I filled up. The odometer showed 581 kms (361 miles) for that tank....filling up with exactly 17 USG. Despite all the pre-trip 'mixed' miles and very little highway driving prior and no real attempt at economy, that got me 21+ miles/USg. (just over 25/Imp. gallon)

I've been real skeptical in the past of gas mileage claims I've seen in some similar threads on this forum, so I'm with you guys for sure. The only thing I can say in defense is how diligent I was today keeping my right foot out of it and I-5 being virtually dead level over that 75 miles. I was shooting to see the max mileage I could get. Not that that means much since no one can ever show that kind of restraint driving a Z. They just beg to be driven with no attempt at fuel economy. I remain skeptical too, but these were the numbers I got.

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Zipper 104

Sorry, but I don't see how resetting this display beforehand would change things?
I was using odometer and fuel consumption numbers to determine mpg. Granted, doing a longer 'sample' distance before topping up might make things more accurate.

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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.

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MagmaRed370z

I have done multiple test and all of them lead to 27-28 mpg highway and 21 city.

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."

__________________
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)

Duc_Z09

That sounds about right... if you're not me, driving at 3500+ all the time and taking on-ramps like a test track.

__________________
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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