GT MPG - First highway trip

[Qwkynuf]

I know that this has come up several times, in different formats, but I wanted to share my experience.

I have a GT with the 50th appearance package, auto, and 3.55.

I had to drive about 275 miles of interstate yesterday, with about half into a strong headwind. Today, I came home, with little to no wind. Posted speed limit is pretty much 65 the whole way.

Since my boss doesn't pay speeding tickets, but *does* pay overtime, I stuck to the posted speed limit in both directions.

At 65mph, the tach is sitting a tiny scootch above 2000rpm.

I filled up right after I left the house yesterday and had to detour for about 10 miles of city driving, which probably reduced the overall mileage by a small amount.

I filled up again today, before heading home. At that time, the indicated mpg for that tank was 22.5. Hand calculated mileage was 21.9. For the return trip, the indicated mpg was 24.5.

The highest I saw was 25.7, for a stretch early on which was 60mph.

The car had 1470 miles on the odometer when I left and 2039 when I got home.

I was able to get 27-ish on the freeway in my '06 V6, so this isn't completely terrible.

Overall average mpg (total miles driven / total gas bought) is sitting at 19.1 hand-calculated and 19.4 on my "Trip 2" screen, which hasn't been reset.

I think that a couple of things factor into the mileage that I can expect - the 5.0 is obviously the biggest factor (combined with how much shoe I stuff into it), the 3.55 rear end is also a factor, but I also think it is important to consider which wheels/tires are on the car, since a wider tire is going to increase the contact patch - which will increase the rolling resistance (and wind resistance by a small amount).

For example, the standard 18x8 wheels use a tire with a 235 section width, which should give roughly an 8" tread width. The 19x8.5s on my car are 255mm section width, so call it an inch wider to make the math easy (it's actually around 3/4"). On the PP cars, the front wheels are 1/2" wider, at 19x9, but the section width is the same 255mm.The rears are another 20mm wider - so another inch-ish of tread width on each tire.

Forgive my rambling, just something to think about.... I would be interested to see if anyone has the same configuration as me and is getting significantly different mpg results.

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[Tamadrummer88]

I know that this has come up several times, in different formats, but I wanted to share my experience.

I have a GT with the 50th appearance package, auto, and 3.55.

I had to drive about 275 miles of interstate yesterday, with about half into a strong headwind. Today, I came home, with little to no wind. Posted speed limit is pretty much 65 the whole way.

Since my boss doesn't pay speeding tickets, but *does* pay overtime, I stuck to the posted speed limit in both directions.

At 65mph, the tach is sitting a tiny scootch above 2000rpm.

I filled up right after I left the house yesterday and had to detour for about 10 miles of city driving, which probably reduced the overall mileage by a small amount.

I filled up again today, before heading home. At that time, the indicated mpg for that tank was 22.5. Hand calculated mileage was 21.9. For the return trip, the indicated mpg was 24.5.

The highest I saw was 25.7, for a stretch early on which was 60mph.

The car had 1470 miles on the odometer when I left and 2039 when I got home.

I was able to get 27-ish on the freeway in my '06 V6, so this isn't completely terrible.

Overall average mpg (total miles driven / total gas bought) is sitting at 19.1 hand-calculated and 19.4 on my "Trip 2" screen, which hasn't been reset.

I think that a couple of things factor into the mileage that I can expect - the 5.0 is obviously the biggest factor (combined with how much shoe I stuff into it), the 3.55 rear end is also a factor, but I also think it is important to consider which wheels/tires are on the car, since a wider tire is going to increase the contact patch - which will increase the rolling resistance (and wind resistance by a small amount).

For example, the standard 18x8 wheels use a tire with a 235 section width, which should give roughly an 8" tread width. The 19x8.5s on my car are 255mm section width, so call it an inch wider to make the math easy (it's actually around 3/4"). On the PP cars, the front wheels are 1/2" wider, at 19x9, but the section width is the same 255mm.The rears are another 20mm wider - so another inch-ish of tread width on each tire.

Forgive my rambling, just something to think about.... I would be interested to see if anyone has the same configuration as me and is getting significantly different mpg results.

This is actually very good to know. I ordered mine with the Foundry wheels (same width as the stock 18's) but with 3.31's and the manual. My commute is short and all freeway. Now i know what to expect.

 

[s550hopeful]

The most I got in my p/p gt was 29.1mpg. I was driving it between 60-70 mph. It was a 50 mile drive, hardly used the brakes and just babied it. It was just a personal test to see the best mileage I could get. Once I hit the street though, it went down quick lol.

 

[clrsky]

I just did a trip on the turnpike down here. About 250 miles. I have GT Premium with 265/35/20s and 3.55 rear. Cruise control at 80 was getting right at 23.0 mpg which I thought was damn good.

 

[Qwkynuf]

The most I got in my p/p gt was 29.1mpg. I was driving it between 60-70 mph. It was a 50 mile drive, hardly used the brakes and just babied it. It was just a personal test to see the best mileage I could get. Once I hit the street though, it went down quick lol.

Is this a peak number (i.e. the highest that you saw during the trip), or was that an average for the whole 50 miles? I ask because the first 50 miles of my drive yesterday was steady-state 60mph driving on more or less flat highways, and I never saw anywhere near that number - and I have narrower tires and a more favorable rear-end gear ratio.

Thanks

 

[Jaxstang]

This was mine on a trip down to Miami last week. This is all highway with adaptive cruise control set at 75 mph. GT with 3.15 rear. :eyebulge:

 

[jdpatt12]

I know that this has come up several times, in different formats, but I wanted to share my experience.



I have a GT with the 50th appearance package, auto, and 3.55.



I had to drive about 275 miles of interstate yesterday, with about half into a strong headwind. Today, I came home, with little to no wind. Posted speed limit is pretty much 65 the whole way.



Since my boss doesn't pay speeding tickets, but *does* pay overtime, I stuck to the posted speed limit in both directions.



At 65mph, the tach is sitting a tiny scootch above 2000rpm.



I filled up right after I left the house yesterday and had to detour for about 10 miles of city driving, which probably reduced the overall mileage by a small amount.



I filled up again today, before heading home. At that time, the indicated mpg for that tank was 22.5. Hand calculated mileage was 21.9. For the return trip, the indicated mpg was 24.5.



The highest I saw was 25.7, for a stretch early on which was 60mph.



The car had 1470 miles on the odometer when I left and 2039 when I got home.



I was able to get 27-ish on the freeway in my '06 V6, so this isn't completely terrible.



Overall average mpg (total miles driven / total gas bought) is sitting at 19.1 hand-calculated and 19.4 on my "Trip 2" screen, which hasn't been reset.



I think that a couple of things factor into the mileage that I can expect - the 5.0 is obviously the biggest factor (combined with how much shoe I stuff into it), the 3.55 rear end is also a factor, but I also think it is important to consider which wheels/tires are on the car, since a wider tire is going to increase the contact patch - which will increase the rolling resistance (and wind resistance by a small amount).



For example, the standard 18x8 wheels use a tire with a 235 section width, which should give roughly an 8" tread width. The 19x8.5s on my car are 255mm section width, so call it an inch wider to make the math easy (it's actually around 3/4"). On the PP cars, the front wheels are 1/2" wider, at 19x9, but the section width is the same 255mm.The rears are another 20mm wider - so another inch-ish of tread width on each tire.



Forgive my rambling, just something to think about.... I would be interested to see if anyone has the same configuration as me and is getting significantly different mpg results.

Do you like the performance from the 3.55? I'm thinking of getting for my convertible.


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[ScottsGT]

Mileage will improve as you break the motor in too. Best I've seen on a 60 MPH back road trip was 27 MPG. Interstate at 70 with 3:55's I'm getting about 24-25. Combined and not horsing around, about 20 MPG. I've got just over 2000 miles on it now.

 

[Streetcar]

This was mine on a trip down to Miami last week. This is all highway with adaptive cruise control set at 75 mph. GT with 3.15 rear. :eyebulge:

That's incredible and why I'm going with the 3.15, 80 at 2000rpm

 

[Oneless70]

GT w/PP. Trip from Augusta Ga to Chattanooga Tn. Swapped to Michelin Pilot Sport All-Season 3, in OEM sizes. 3.73 final drive, 70-80 mph most of the way, mid 50-s temps on average, 93 octane ethanol-free, very little naughty behaviour. Trip computer gave me 26+ mpg on the way up, just under 25 on the way down.

 

[s550hopeful]

Is this a peak number (i.e. the highest that you saw during the trip), or was that an average for the whole 50 miles? I ask because the first 50 miles of my drive yesterday was steady-state 60mph driving on more or less flat highways, and I never saw anywhere near that number - and I have narrower tires and a more favorable rear-end gear ratio.

Thanks

That's the highest I got it to. I felt like I could've gotten up to 30 mpg, but there's was a few times were I accelerated to pass.. and it would drop it down, then it would go up once I drove normal again. I was pleasantly surprised.

 

[YvonneOfTheYukon]

I averaged 28.2 mpg over a 3.5 hour drive at 75 mph in 6tg at 2250rpm this weekend. GTPP with 1200 or so miles on it. When i drive back tomorrow i will see if i can repeat the same milage. It is supposed to be -35 celcius tomorrow im not sure how much that will affect things.

 

[Todd15Fastback]

I drove 870 miles from Lansdale, PA to Charlottesville, VA to Atlanta, GA after picking up my new '15GT PP. I averaged 23.1 MPG that trip. This includes horrible stop and go traffic thru DC.

Very happy with that mileage for a brand new car with 22.8 miles on the odo.

 

[Tim Hilliard]

:lol:

Where are all those people that were going to cancel their orders and wanted to Burn Dave at the stake because the EPA rating was less when he said the car was more effiecient. Did these people actually but a car.

I've gotten 25.4 on 93 (10%Ethanol Crap) on a 100mile non-flat trip@70MPH with my PP with low miles. "Regular" driving combined has gone from 12 to around 20-23MPG on about the 5-6 tank of fuel and 1500-1600 miles.

 

[Todd15Fastback]

:lol:

Where are all those people that were going to cancel their orders and wanted to Burn Dave at the stake because the EPA rating was less when he said the car was more effiecient. Did these people actually but a car.

I've gotten 25.4 on 93 (10%Ethanol Crap) on a 100mile non-flat trip@70MPH with my PP with low miles. "Regular" driving combined has gone from 12 to around 20-23MPG on about the 5-6 tank of fuel and 1500-1600 miles.

I find it funny people complaining about gas mileage on a high performance V8. Doesn't make sense to me but that is just me.

Tim, your post above is spot on. I remember those posts quite vividly and :lol::lol::lol::lol: when reading them.

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