Fuel Economy...WTF?

spearfish25 · 07-03-2009, 08:18 AM

So many of the threads I read have people listing their fuel economy in the 22-25 mpg range. These same folks say they do a mix of city and highway driving. All I can say is I get NOTHING close to this.

I drive about 5 minutes on city streets (stop and go signs and lights) and about 10 more minutes on the highway at about 80mph. I routinely reset my trip computer with each gas up and the average MPG read on the computer is about 16mpg. I drive fairly sporty, but that is usually just revving to about 4k in a few gears some of the time, a rare 5-6k each trip home, and the rest of the shifts around 3k. One tank of gas I drove like a grandma and got 20mpg on my daily route. Granted, if I sit on the highway at 70mph I'll get about 25-26mpg. Worst fuel economy on the daily route...14mpg averaged over the tank of gas.

Is this what you guys realistically get as well, or do i need a trip to the mechanic? FWIW, I'm using 93 octane Shell.

m4a1mustang · 07-03-2009, 08:25 AM

Short drives don't yield the best fuel economy. The car needs to warm up.

spearfish25 · 07-03-2009, 08:42 AM

Quote:

Originally Posted by m4a1mustang

Short drives don't yield the best fuel economy. The car needs to warm up.

That's probably part of the issue...I don't get to 180F oil temps until about half the drive is done.

Cjanik · 07-03-2009, 08:52 AM

dont use the computer trip/mpg to calculate, instead, fill your gas to full, reset your trip mileage, then fill up again when you run low on gas and divide the miles you drove to the gallons of gas you just filled your car with.

that should be more accurate. my tacoma gets 19mpg average, so i dont see why the Z should be getting worse.

sig11 · 07-03-2009, 10:18 AM

I would try different fuel too. It's possible that the station you fill up at has poor fuel; Shell station or not.

frost · 07-03-2009, 10:49 AM

Quote:

Originally Posted by Cjanik

dont use the computer trip/mpg to calculate, instead, fill your gas to full, reset your trip mileage, then fill up again when you run low on gas and divide the miles you drove to the gallons of gas you just filled your car with.

that should be more accurate. my tacoma gets 19mpg average, so i dont see why the Z should be getting worse.

Not a bad idea to at least test how accurate it is. My drives are always a bit longer, but I never get under 25mpg fwiw, and I drive like a nut.

AutoX Z · 07-03-2009, 10:50 AM

I have a 30 minute commute, about 20% city 80% highway. I average between 70 to 20 mph on the highway portion depending on traffic and I get a dead consistent 20-21 mpg even with gunning it onto the freeway.

Also don't trust the trip computer. From my calculations its about 1 mpg low on every tank so far.

spearfish25 · 07-03-2009, 10:57 AM

Hmm, all good points. I'm going to top off the tank today and do the math. Will also fill up at a nearby BP instead of the usual Shell.

frost · 07-03-2009, 10:59 AM

Good luck mate, keep us posted

Nikon FM · 07-03-2009, 11:02 AM

Just after filling up go for a long highway drive somewhere and then compare. I bet the mpg will be significantly better.

GMZ · 07-03-2009, 11:04 AM

Quote:

Originally Posted by Cjanik

dont use the computer trip/mpg to calculate, instead, fill your gas to full, reset your trip mileage, then fill up again when you run low on gas and divide the miles you drove to the gallons of gas you just filled your car with.

that should be more accurate. my tacoma gets 19mpg average, so i dont see why the Z should be getting worse.

This ^ I got 19 mpg combined in my 4Runner as well. I stopped calculating mpg, my new method is time between fill ups. 1/2 tank per 2 full weeks is a good amount for me.

theDreamer · 07-03-2009, 11:08 AM

I have not even looked at what my MPG is since I bought this car, I do with GMZ does. I base my usage on time between fill ups. I always fill up on Mondays now, but if I am above half then I had a good week, below...well we know I might have had some fun.

Zcott · 07-03-2009, 11:11 AM

For what it's worth, I never trust the trip computers so I always to the math on my vehicles (just a habit).
My first two fill-ups the computer was dead on to the tenth.
22.5, and 23.3.

I've found that how I drive around town profoundly affects the mileage.
(I know, not a revelation)
Lord it's hard to stay off that pedal at lights!!!

dszombiex · 07-03-2009, 11:56 AM

I just started gathering data. Here is what I have so far...

TheWeatherman · 07-03-2009, 11:58 AM

Hey Spear... From what I've found with my '09 FX35 and this, the VQ motors don't start getting their best mileage until they are fully warmed up. When I just have my 15 minute trip to work, your mileage is close to what I'm getting. Once both of them are warmed all the way, the mileage goes way up. Just an observation for what it's worth.

07-03-2009, 08:18 AM	#1 (permalink)
spearfish25 A True Z Fanatic Join Date: Mar 2009 Location: Naples, FL Posts: 4,117 Drives: to work Rep Power: 1856	Fuel Economy...WTF? So many of the threads I read have people listing their fuel economy in the 22-25 mpg range. These same folks say they do a mix of city and highway driving. All I can say is I get NOTHING close to this. I drive about 5 minutes on city streets (stop and go signs and lights) and about 10 more minutes on the highway at about 80mph. I routinely reset my trip computer with each gas up and the average MPG read on the computer is about 16mpg. I drive fairly sporty, but that is usually just revving to about 4k in a few gears some of the time, a rare 5-6k each trip home, and the rest of the shifts around 3k. One tank of gas I drove like a grandma and got 20mpg on my daily route. Granted, if I sit on the highway at 70mph I'll get about 25-26mpg. Worst fuel economy on the daily route...14mpg averaged over the tank of gas. Is this what you guys realistically get as well, or do i need a trip to the mechanic? FWIW, I'm using 93 octane Shell.

07-03-2009, 08:25 AM	#2 (permalink)
m4a1mustang A True Z Fanatic Join Date: Feb 2009 Location: Northern VA Posts: 55,385 Drives: on two wheels Rep Power: 6962	Short drives don't yield the best fuel economy. The car needs to warm up. __________________ - Steve Zs & Coffee - Saturdays at 10AM in Fairfax, VA and Columbia, MD (Click the banner!) LIKE us on Facebook!

07-03-2009, 11:02 AM	#10 (permalink)
Nikon FM Track Member Join Date: Jan 2009 Location: Snoqualmie WA Posts: 973 Drives: 03 996TT Porsche Rep Power: 606	Just after filling up go for a long highway drive somewhere and then compare. I bet the mpg will be significantly better. __________________ Buddy Revell: "One man's sooner is another man's later"

07-03-2009, 11:08 AM	#12 (permalink)
theDreamer A True Z Fanatic Join Date: Feb 2009 Location: Texas Posts: 30,879 Drives: 370z Rep Power: 4210	I have not even looked at what my MPG is since I bought this car, I do with GMZ does. I base my usage on time between fill ups. I always fill up on Mondays now, but if I am above half then I had a good week, below...well we know I might have had some fun. __________________ theDreamer's Z // Fast Intentions // Uprev // GTM // HKS // TEIN theDreamer's Silvia // URAS // GREDDY Houston Zs // Facebook // Twitter // Instagram

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07-03-2009, 08:52 AM	#4 (permalink)
Cjanik Track Member Join Date: May 2009 Location: Las Vegas Posts: 578 Drives: N/A Rep Power: 17	dont use the computer trip/mpg to calculate, instead, fill your gas to full, reset your trip mileage, then fill up again when you run low on gas and divide the miles you drove to the gallons of gas you just filled your car with. that should be more accurate. my tacoma gets 19mpg average, so i dont see why the Z should be getting worse.

07-03-2009, 10:18 AM	#5 (permalink)
sig11 A True Z Fanatic Join Date: Jun 2009 Location: Detroit Posts: 1,294 Drives: 09 370Z Red Sport-MT Rep Power: 18	I would try different fuel too. It's possible that the station you fill up at has poor fuel; Shell station or not.

07-03-2009, 10:50 AM	#7 (permalink)
AutoX Z Enthusiast Member Join Date: Jun 2009 Location: Houston, Tx Posts: 314 Drives: 370Z Base, Sport Rep Power: 16	I have a 30 minute commute, about 20% city 80% highway. I average between 70 to 20 mph on the highway portion depending on traffic and I get a dead consistent 20-21 mpg even with gunning it onto the freeway. Also don't trust the trip computer. From my calculations its about 1 mpg low on every tank so far.

07-03-2009, 10:57 AM	#8 (permalink)
spearfish25 A True Z Fanatic Join Date: Mar 2009 Location: Naples, FL Posts: 4,117 Drives: to work Rep Power: 1856	Hmm, all good points. I'm going to top off the tank today and do the math. Will also fill up at a nearby BP instead of the usual Shell.

07-03-2009, 10:59 AM	#9 (permalink)
frost Retired admin Join Date: Dec 2008 Location: Winterfell Posts: 106,613 Drives: Your Wife Crazy Rep Power: 0	Good luck mate, keep us posted

07-03-2009, 11:11 AM	#13 (permalink)
Zcott Base Member Join Date: Jun 2009 Location: D/FW, Texas Posts: 89 Drives: 09 370Z Sport PG M6 Rep Power: 16	For what it's worth, I never trust the trip computers so I always to the math on my vehicles (just a habit). My first two fill-ups the computer was dead on to the tenth. 22.5, and 23.3. I've found that how I drive around town profoundly affects the mileage. (I know, not a revelation) Lord it's hard to stay off that pedal at lights!!!

07-03-2009, 11:58 AM	#15 (permalink)
TheWeatherman Enthusiast Member Join Date: Mar 2009 Location: Milwaukee, WI Posts: 265 Drives: 2009 370Z 6MTw/Sport Rep Power: 16	Hey Spear... From what I've found with my '09 FX35 and this, the VQ motors don't start getting their best mileage until they are fully warmed up. When I just have my 15 minute trip to work, your mileage is close to what I'm getting. Once both of them are warmed all the way, the mileage goes way up. Just an observation for what it's worth.