.29 drag coefficient + average speed

[AlcyoneDaze]

I've read that driving between 55-65mph will net the best fuel consumption out of most passenger vehicles, since speeds above 65mph increase drag exponentially...

now, does the fact that our car is so 'slippery' do anything to bump that number up, perhaps making the best average crusing speed for gas mileage any higher, say; 70+mph?

[It's Just Eric]

good question.

Figure they probably conducted that study when they were setting the highway speed limit (40's, 50's?) and cars drove MUCH diffrently back then. Everything from final drive ratio to the previously mentioned drag coefficiant...to how much air goes in the tires...has an effect on the corelation between gas mileage and distance covered compared to speed. I would imagine the only way to figure out exactly what speed you're getting the best gas mileage is to have an awd dyno, an extreamly accurate trip odometer, cruise controll, and some very effective way of measuting fuel consumption. You'd need to put the whole thing in a wind tunnel to mimick airflow while moving

this whole experiment would only yeild one result....Miles per gallon is such a vauge fuel consumption measurement...its retarted. I honestly think the only true way to measure fuel efficiancy is to measure it by liters/hour@X RPM under full load (Including properly inflated tires on a rolling road, and for practicality sake 200 additional pounds in the car representing a driver and misclanious stuff) Of course, every vehicle would be tested at multiple RPM's to actually graph fuel consumption per RPM...and it is with THIS raw evidence that you can actually figure out what speed your convering the most distance per ounce of fuel consumed

Now, becasue I've overthought this WELL into the point where everyone reading fell asleep,( except a few choice engineers, perhaps)Ill just go ahead and say **** counting your drops of gasoline and just drive whatver speed you and your car are comfortable with.

[AlcyoneDaze]

yea... but my tank goes down too fast @ 140

[dcarrb]

I routinely get fuel mileage in the high 20s at 70+MPH (in Atlanta that's just going with the flow and not getting blown into the weeds), but I still believe the MPG numbers would be a bit better at 55 to 65. Trouble is, I can't make myself drive at those speeds to test that belief.

dcb

[benebob]

I've gotten close to 40mpg in my XT6 (same drag as the SVX). Best is still around 50-55mph on the highway. Without caring about mileage I was getting around 30mpg driving the same routes around the same times in the same weather with the same gas (very important as the brand of gas can effect your mileage by about 10% and each of my cars does better with a different kind of gas!). I'm sure if I went 40mph I could've topped 40mpg. Drag is drag no matter what the vehicle is. Sure it might not decrease your mileage 20% going from 55 to 75 but it'll still decrease it a very large percent. AC is horrible in town, better or equal to having the windows open once you reach about 40. Better still if you can drive without it.

I currently get around 28ish or so in my 6 as I'm now sporting a 3.9 geared 5 speed vs a 3.7 auto. Auto killed the 5 in mileage!

[RSVX]

Mythbusters recently had an episode where they tested MPG with and without AC... they found that at both high and low speed, you are better off with the AC on...

[SSSVX]

Any formula to calculate how much/percent hp the AC taking from your engine?

On the small car/engine, I can really feel the AC taking quite some power on going up hills. On the bigger engine, it's less obvious.

[benebob]

Originally Posted by RSVX

Mythbusters recently had an episode where they tested MPG with and without AC... they found that at both high and low speed, you are better off with the AC on...

Didn't see it Chris as TV bores me but since you didn't finish you're sentence. While in an urban setting its idiotic to think that adding yet another strain to an idling engine is better than not having it on. Also, despite you're incomplete thought it of course is better to not have it on and drive with the windows shut at any speed.

[Kelvin]

Originally Posted by RSVX

Mythbusters recently had an episode where they tested MPG with and without AC... they found that at both high and low speed, you are better off with the AC on...

Only with the windows UP. Windows down= more drag= less MPG.