optimal fuel efficiency speed

[tomspec]

Does anyone know the speed at which you should get optimal fuel efficiency on an '06 Vibe FWD Auto?

[GrayFox]

I don't know the offical speed or if there even is one, but I would guess it would be 55 or lower. Pretty much whatever speed gives you the lowest RPMs in the highest gear.

[AKLGT]

i don't know but it seems we get the best fuel economy in Mav's 5spd about 60 mph.. steady, without accelerating or decelerating.

[northvibe]

I know for sure when you go over 65mph you start creeping over 3k rpm which means the bad mileage will start rearing its ugly face fast Basically you just want to keep under 3k rpm all the time and you'll get good mileage.

[ZubenElGenubi]

ANO_Vibe is right; you'll get the best fuel efficiency when in the highest gear (i.e., Overdrive/4th gear) and the lowest speed (about 40 mph).However, I'm seeing the best average MPG results on my ScanGauge when driving around 45 mph. I think this is because there is a less torque at 40 and the engine has to work a little harder. Admittedly, I haven't run any controlled tests, but now that my interest is piqued....

[ColonelPanic]

I did a bit of checking when I had the Vibe, using the real time MPG gauge on the ScanGauge. IIRC, it was peaking somewhere between 45-50 MPH but it's been so long, I can't say for sure. It was interesting to see how poorly it was doing at the slower speeds. And of corurse, once you take it up too far the engine still needed a workout to keep up, so the numbers suffered there as well.

[GrayFox]

Quote, originally posted by ZubenElGenubi »ANO_Vibe is right...Wow, I need to show this to my wife

[Johnny5]

What are you all considering "good" mileage? I made a trip to Canada doing 80 with the A/C on and got like 30.X mpg. I've seen closer to 34 with just mixed driving no a/c and keeping the speed down to 65 or less.What do you think the max is?

[tomspec]

I recently got 35.5 MPG on "secondary" type highways going between 80 and 100 km/h (50 and 62 MPH.) That was over about 300 miles.

[GrayFox]

Quote, originally posted by Johnny5 »What do you think the max is?http://forums.genvibe.com/zerothread?id=24519This member reports the max that they got was 41 MPG in a GT

[Johnny5]

I would think that as long as you are seeing over 30 I wouldn't raise an eyebrow on these cars.If you are honestly trying to get the max mpg out of every tank then that is another story or even if you are modding it to increase that number. (then we all want to know what you did... like pouring in some secret sauce to the tank etc.)41mpg is great unless the person stripped the car of the interior and only drove between 1000-2200 rpm for the tank of gas

[ZubenElGenubi]

Okay, here's the results of my first set of runs @ 40 mph. I used the ScanGauge to record the MPG once the speed stabilized (used Trip mode, Current). Two runs, about 1.5 miles each, one northbound the other southbound on same street (to account for any wind/slope difference). Average MPG on first run was 43.3; average MPG on second run was 44.7. Overall average: 44 mpg.I'll update with higher speed tests...

[GrayFox]

WOW, no more speeding for me of course, in-town that would be speeding

[tomspec]

Very interesting.Now 1.5 miles seems like a pretty short test. Do you think the data would be much different after the engine is REALLY warmed up? It doesn't seem right to me that your optimal fuel efficiency would occur under 50 MPH, but that's why I asked...

[GrayFox]

Quote, originally posted by tomspec »It doesn't seem right to me that your optimal fuel efficiency would occur under 50 MPH, but that's why I asked...The higher your speed is the more power you need to maintain that speed, but right around 40-50mph is that sweet spot where you get the lowest rpms (greatest MPG) in 4th gear. (based on Zuben)saddly, that sweet spot is hardly ever doable. In the city you're constantly starting and stopping and on the road you (me) really don't want to go that slow.And zuben also has mods like a CAI that could impact his findings so far.

[Vibr8tr]

Once O/D really kicks in, my RPM's are nothing. I get to 60 and my RPM's are only at 15-2000. I can cruise at 80 and keep it under 3K. I have found that on the expressway I get about 35-36 MPG, but when I am in the city and "drive it like I stole it", I only get about 28-30..... Should I maybe let off the gas some?

[GrayFox]

Quote, originally posted by Vibr8tr »Should I maybe let off the gas some?lol, confusous say "Man with lead foot has lighter pocketbook"How high do you let the RPMs go when your driving like that?

[ZubenElGenubi]

Quote, originally posted by tomspec »Very interesting.Now 1.5 miles seems like a pretty short test. Do you think the data would be much different after the engine is REALLY warmed up? It doesn't seem right to me that your optimal fuel efficiency would occur under 50 MPH, but that's why I asked...Well, it was actually 3 miles total. But, yes; we really need a much larger sampling of data. I'm doing that now (well, not right this MOMENT). I'll make several runs at speeds from 40 to 75 mph and try to get 5-10 miles of measurements at each speed at the very least. Then, I'll use weighted averages of the results to get an everage MPG per MPH.Regarding your last point, it actually does make sense that the optimal fuel efficiency might be below 50 mph, as I'm sure that most Vibe owners drive less than 50 mph on average. My average speed for each tank (as measured by the ScanGauge) is actually around 30-35 mph.

[ke4yyd]

I have been watching my Scan Gauge carefully since I got it and have adjusted my driving habits acordingly. There is no doubt that the mpg improves at speeds less than 60 mph. I have tied runs of 50 miles or more at 60 mph, 55, mph, 50 mph and 45 mph and the 45 mph proves to be the best. These runs were made in a FWD Auto with AC on with Cruise Control.I can't stand driving 45 mph but I can force myself to stay at 50 mph. At 50 mph 95% highway I got 39.5 mpg on my last tank.