Better mileage at 80mph Vs. 60mph in a V10!??
Fleet Mechanic
Joined: Aug 2006
Posts: 1,684
Likes: 0
From: Phoenix, AZ
Where, a 15 mph school zone? Having gotten cited for 85+ mph in a number of jurisdictions, I've merely been required to donate to the donut fund. I haven't seen a single instance where, on an interstate in a 65 mph zone, you can get jailed and have your vehicle impounded for 85 mph. Doesn't mean they don't exist, just means I haven't encountered them. Either way, I don't see how that relates to the laws of physics.
686, believe it or not, there are places in the US where 85 might get you rear-ended or shot... Take a trip down to Phoenix some time...
Sit. Stay.
Joined: Oct 2001
Posts: 18,308
Likes: 20
From: Washington State
And in your case; EITHER! 
While I can understand that the V10 (or any engine) has a "sweet spot" and that the aerodynamic profile probably also has a sweet spot to where the low pressure up front is enough to actually push air up and over reducing drag a bit even though aerodynamic drag SQUARES at speed and probably at a certain speed the tires increase in diameter enough due to centripetal force to help reduce the foot print a tad, I still find it hard to wrap my head around the notion that the faster you go the better the mileage.
Many folks have claimed it but I, personally, have never seen it in either of my Excursions. Maybe I'll go try this weekend on a certain flat section of road here.
While I can understand that the V10 (or any engine) has a "sweet spot" and that the aerodynamic profile probably also has a sweet spot to where the low pressure up front is enough to actually push air up and over reducing drag a bit even though aerodynamic drag SQUARES at speed and probably at a certain speed the tires increase in diameter enough due to centripetal force to help reduce the foot print a tad, I still find it hard to wrap my head around the notion that the faster you go the better the mileage.
Many folks have claimed it but I, personally, have never seen it in either of my Excursions. Maybe I'll go try this weekend on a certain flat section of road here.
Mountain Pass
Joined: Jun 2006
Posts: 197
Likes: 0
Lower RPMs doesnt always mean better fuel economy. (don't know about this case, just a general statement) The old cars that used to have an economy meter on the dash used engine vacuum to find the best economy. It did not equate to the lowest rpm. I used a vacuum guage on my 68 to get better economy and it worked.
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Mountain Pass
Joined: Jun 2006
Posts: 197
Likes: 0
With all the computer controlled fuel injection, I am not sure if it would help with these new engines, but on old carburator engines you would just run a normal vacuum gauge off your manifold. Keep the vacuum at the highest pressure and you would get your best milage. In regards to this thread, I was only mentioning it to say that there is a "sweet spot" for milage and it is not always at the lowest rpm.
Fleet Mechanic
Joined: Aug 2006
Posts: 1,684
Likes: 0
From: Phoenix, AZ
I donno about the 60 vs 80 thing, but it is possible to get better MPG going faster than slower
Luckily, they can fix looks nowadays relatively easy... now for the other part...
Thread Starter
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Posting Guru
Joined: Sep 2001
Posts: 1,539
Likes: 3
Keep resetting fast enough and you have an instant gauge as well! lol
I am having trouble wrapping my brain around this faster = better fuel economy thing as well, thats why I posted up for other opinions. Now that I see others have noticed teh same, it intrigues me quite a bit more.
More fuel for the fire, air temps were around 55 degrees during that trip. Seems these trucks make a very noticable amount of extra power at cooler temps then warm. Thats true for pretty much any motor I know, my old olds 307 was the same way, just this V10 does it more so then any other motor I have owned. Maybe its due to the displacement?
I am having trouble wrapping my brain around this faster = better fuel economy thing as well, thats why I posted up for other opinions. Now that I see others have noticed teh same, it intrigues me quite a bit more.
More fuel for the fire, air temps were around 55 degrees during that trip. Seems these trucks make a very noticable amount of extra power at cooler temps then warm. Thats true for pretty much any motor I know, my old olds 307 was the same way, just this V10 does it more so then any other motor I have owned. Maybe its due to the displacement?
