Driving 55mph? (Is it the most efficient speed?)

[JoeBob]

I seem to find that about 55 for my Geo (with automatic...no overdrive) and about 60 for my '83 Eldorado (with overdrive in the automatic) seem to give about the best mileage. Mind you, this is anecdotal, not scientifically verified.

[8307c4]

Yes and just like in the late 70's / early 80's there is going to be MUCH ado about this until the government REGULATES the speed limit forcing ALL of us to do what they say like it or not.

55 saves gas, that's all there is to it.
However, this thread fails to take into account certain key issues:
- Every car is different, some might get as good mpg at say 58 mph...
My '88 T-bird used to get its best at 62-63.

And the gearing does make a difference too, most of today's cars are BUILT to race... It's not that you get better mpg at 70, it's that it feels RIGHT to do it because the gears in the transmission just make the car cruise like that.

But just because mine LIKES to do 80 and 90 doesn't mean I do it.
Because wind resistance at much over 60 is what kills it all.

[PA32R]

Originally Posted by 8307c4

Yes and just like in the late 70's / early 80's there is going to be MUCH ado about this until the government REGULATES the speed limit forcing ALL of us to do what they say like it or not.

55 saves gas, that's all there is to it.
However, this thread fails to take into account certain key issues:
- Every car is different, some might get as good mpg at say 58 mph...
My '88 T-bird used to get its best at 62-63.

And the gearing does make a difference too, most of today's cars are BUILT to race... It's not that you get better mpg at 70, it's that it feels RIGHT to do it because the gears in the transmission just make the car cruise like that.

But just because mine LIKES to do 80 and 90 doesn't mean I do it.
Because wind resistance at much over 60 is what kills it all.

But what else will then be regulated? I've blogged extensively about the single minded, goal oriented, participatory behaviors that I think will be required to get us through the coming energy shortages with minimal (but certainly not zero) trauma. Think World War 2 and the types of rationing that people alive in that time voluntarily tolerated because they agreed with the goal.

But convincing people to participate, as difficult and unlikely as that is, is the only way to success. Once government (Democratic, Republican, liberal, conservative, local, regional, or national) gets the regulation "bit between their teeth," it won't stop with measures such as that. The irrational responses would be amazing. Witness the gas tax holiday, the "stop filling the strategic oil reserve" strategy, etc.

I don't know what it will take, but I don't think a nationwide 55 m.p.h. speed limit is a good start. It is, however, marginally higher than I set my cruise control. That said, as mentioned in my previous post in this thread, my best mileage speed is something near 43 m.p.h.

[Chris D.]

this is strange.. my SGII says I get the same if not better MPG at 70 vs 55???

I made this quick video.. Only thing I can think of is that I mite have had a tail wind?

I wasn't going downhill (till the last few seconds of the video) and no drafting.. ???

http://www.youtube.com/watch?v=o9OdhwZtncc

[MetroMPG]

Couple of comments, ChrisD:

1) I find it's REALLY hard to get an accurate picture of what mpg I'm getting by using the "instant" readout because it fluctuates constantly with even the slightest movement of the throttle. EG: I saw yours also reading 42.x and 48.x in the video.

The most accurate way to do this is to drive the same stretch of road at different speeds and reset the "current" (averaging) readout at the same point, and take your reading at the same finishing point. Average multiple runs to get the highest quality information.

2) There's a car about 2 seconds ahead of you. At 70 mph, you may be benefitting somewhat from a distant draft situation.

The best way to know for sure what is your truck's "max mpg" constant speed is to do a controlled-as-possible test.

[Chris D.]

oh, ok.. I'll check that out.

I'm still trying to figure out the SGII tho, can't get the cutoff right..

whats the default setting for fuel cutoff?

[DifferentPointofView]

Can I have your vacuum gauge now that you have that?

My vacuum gauge was crap and now I've spent almost as much on shipping in returning it for a replacement as I was spending on the gauge itself!!!

Hopefully the one I get back is good, or else I'm gonna be pissed off.

[Chris D.]

lol

I still use it actually, on the fly corrections for over throttling..

[ojman873]

In lieu of having an actual BSFC map for one's particular engine, would the Gallons/hour setting on the scangauge be a fairly good indication of how efficient your speed is?

Usually when I'm cruising on the interstate, the GPH readout is between 1.4 and 1.8 GPH; but it also reads similar number quite often at lower speeds, like suburban streets at 45 mph...

[JoeBob]

Originally Posted by JoeBob

I seem to find that about 55 for my Geo (with automatic...no overdrive) and about 60 for my '83 Eldorado (with overdrive in the automatic) seem to give about the best mileage. Mind you, this is anecdotal, not scientifically verified.

Interestingly, I just spent an evening driving a couple hundred miles about 3 weeks ago (don't ask why!)...since the roads were pretty empty, and I wasn't in a hurry (really pissed off and listening to Art Bell) I tried to hold my speed to around 45. Normally I get in the high 30s for mpg. On that tank, I got almost 44 mpg. Again, anecdotal, not scientific. But an indication.