Acinonyx

...What's up with the mileage difference between V8's? Especially the GT's lack thereof.
No complaints, just curious.

I know this sounds crazy, but in my head, more displacement=less mileage, generally because of the fuel required to move the larger rotating assembly. At least to my understanding.

Also, lower RPMS=less fuel used. Pretty much the same concept as above

So why is it, that in my SS camaro I can pull 26 miles to the gallon (real world measured based on miles divided by gallons put in to top it off) A 5.7 liter motor

Whereas in the Mustang GT, a 4.6 liter motor, driven the same way, I get roughly 15 miles to the gallon.

Similarly my friends 4.6 liter northstar auto 1986 STS gets about 22 miles to the gallon

The Dodge charger R/T I rented got about 17 miles to the gallon, at a 2000 foot elevation.

The previous generation 4.6l GT got about 17 as well (only tested on automatic)

The driving was a combination of city and highway, averaged out.
The SS was the only manual car. however of all of these cars, the mustang has one of the smaller displacements, and had the lowest RPM range at freeway speeds. Drag Coefficient doesn't seem to be a factor in this seeing as the mustang had one of the lower ratings. It's also one of the lighter fully loaded cars.

So why is this? Is it due to the architecture of the valvetrain? Is it computerized timing? I don't know the specifics of most of the motors, but the old Modular was DOHC, the Northstar is DOHC, the Charger has the MDS displacement on demand, and I can't quite tell whether it's a pushrod or what from the cutaways. the SS had the pushrod, and finally the new mustang has the SOHC.

Thanks

hammeron

i would only submit that since it's likely that the newer 4.6L engines
are more efficient then the older V8's, perhaps it's mainly a weight
and gearing issue.....

who knows, good question tho



"in my SS camaro I can pull 26 miles to the gallon "

cekim

My theory based on the 2 cars in my sig which gives me roughly the same comparison is that we are seeing/suffering from the power per liter/ci we are getting out of these engines...

They get their oomph at higher RPMs so your foot accomodates this by pushing harder...

Where the 350+ engines start the fun at 2000RPM, these 281's start over 3000.

It is not that they cannot get better mileage, it is that to match the same G's you are seeing higher RPMs. Does not help that this car is really heavy...

I can also add a data point of the wife's 911 3.4L 300HP engine. A 2800lb car gets about the same mileage as the mustang, but does it with style...

I bet if you drive both at the same actual rate of acceleration as a neon, the smaller engine would do better, but I have no interest whatsoever in proving that point. Every failure to accelerate is a wasted chance that you won't get again...

HypromanGT

Another interesting data point that continues to blow my mind: I used to own a '94 Buick Regal with a 3.8L V6...heavy heavy...got 31-33 miles per gallon highway. Why? At 75MPH it was taching about 2,000RPMs. At the time my girlfriend had an Olds. Alero with a 3.0L V6 (I think), lighter, but she couldn't touch my highway gas mileage because it was geared lower. Then again, it would get up and go a bit quicker than my rig, so...it's all about tradeoffs.

custom interior

newbie at this forum stuff, but here goes. i just got back from a 2000 mile trip with our 06 gt, at an average of 77 mph, my car got 22 miles to the gallon. i'm not, repeat, NOT an easy driver, and i still got 22! thats with 87 octane, four people, and a trunk loaded full of stuff. when i tried real hard, i got 26, again, drafting, 62 mph, smooth, no cruise control... the rpm's on the 77 mph averages were about 2200. my car has the 5-speed. by the way, the info computer is awesome, and right on, only 1/2 mile off of my GPS on the long run. totally happy, you might re-check your figures, also, no mods done to my car yet...

cekim

The GPS has error in it as well... Over a long distance, straight-line approximations and the multi-satelite source interpolations of your position will introduce error in its computation...

The car wil have some error related to tire inflation.

As for checking figures - nope - don't need to - I could easily get > 22MPG with a carburated 351 in my '85 loaded down on the highway at ~75MPH...

If you drive nice (and cruising along at a steady 77 qualifies), you can get great mileage, but smile-for-smile the 4.6 consumes just as much if not more gas owing to higher RPMs required for equivalent fun...

Stooge

Check your right foot - the master controller of gas mileage. Then check your left foot; is it the "speed controller" or the "brake pedal." Then check your brake pads. Are you replacing them every 20K?? Bottom line, driving technique trumps all in the area of gas mileage.

cekim

[sm=WTFsgign.gif][sm=chairshot.gif]
No braking with your left foot! Stop it now! Who ever taught you to drive should be spanked and if I am behind you in the Explorer, I may have to ram you
[sm=joke.gif]
I assume you were being metaphorical?

xzo6

My car gets poor mileage in stop and go City driving.On the turnpike it gets 24 to 25 miles(AVG.) to the IMPERIAL gallon which is 4.5 litres(this means my gallons are slightly larger than an American gallon).If I don't go over the 60mph mark on the hiway and don't hit the throttle hard it will do slightly better.Drive the car hard I gets a lot less...(partially due to having a blower and a rich programmed ECU).The point being that if you want better miles to the gallon you have to stay in one lane and grit your teeth as you let all those other cars and trucks pass you.[:@]

Menace

City driving strictly? Probably like 11mpg. HWY Driving? Probably 23mpg. A light mix of both, with mostly HWY? 20 mpg. Sucks...