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Discussion Starter #1
What has everyone been getting in terms of mileage on 75 mph freeways, without drafting? I have a 2000 Manual Transmission, normal tire pressure.

A few days ago I was on my way home for the weekend and averaged 64.1 mpg from Prescott, AZ to Holbrook, AZ (through Flagstaff). During this time, my speed ranged from 70 to 85, but mostly was around the 80 mark. I know the mileage isn't spectacular, but at 80 mph and the usual heavy cross-winds, I was impressed.

Keep in mind: I-17 up to Flagstaff isn't very nice on low-powered vehicles and has a net gain of about 2000-3000 ft. The rest of the trip was about level, but still 80 mph.

Maybe this has been discussed before, but I couldn't find anything and was rather curious.

In summary:
What is average mileage at 75-80 mph without drafting, and on what types of roads?
 

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I don't have any recorded numbers, but they're in the 70-80 mpg range in the summer. City driving is so much worse that just getting onto the highway is a relief. Ideally the highway speed limit will eventually be set back to 55 mph at which point we'll be able to both keep up with traffic and maximize economy.
 

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Last summer, I drove from Richmond, VA to Blacksburg, VA and back. About 200 miles each way through some pretty hilly terrain and substantial mountains (for the East Coast). I probably climbed 2000-3000 feet. I drove about 72-75 mph with two people in the car and the a/c on much of the time. I think I averaged 58 mpg. I can make the trip to Charlottesville (smaller but rolling hills) at 55-60 mph with no a/c and get 75 mpg. I would guess that the air conditioning was costing me 8-10 mpg and the speed was the remaining 7-9 mpg. So, without air, I would say I would have gotten 66-68 mpg (maybe a bit optimistic).

My tires were probably 45-50 psi

I would say that your 64.1 is reasonable.

HTH

Jim
 

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I drove my Insight from Phoenix to Prescott occasionally and to Flagstaff a few times. Personally I would not expect mileage like that at those speeds. I usually would get around 55mpg going to Prescott and 80mpg on the way back doing 75 at least the whole way.

Of course all cars are a little bit different.
 

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Discussion Starter #5
I have driven the same road multiple times, and I recall getting about that mileage. 55 mpg up, unless traffic is stop and go always up Sunset Point, then it drains the battery like no other and takes a pretty serious hit on mileage. This, of course, only occurs when there is a wreck; it wasn't a fun experience. I don't think I quite get 80 mpg on the way down to Phoenix, but I know it is somewhere close. I don't drive with A/C on, unless I have a passenger (for their comfort, to be sure).

I have heard that A/C takes a hit of about 5 or 6 mpg, not quite the 8 or 10 as JTMCO suggested, but I can't back that with experience. There are many variables, to be sure, humidity in AZ and VA vary quite a bit. But, for the time of year, I guess my experience isn't too bad.

Now that I am back in Show Low, I would guess that I am getting 70-73 mpg (city), and it certainly isn't summer temperatures. It has been snowing the past day or two. Granted, for a city there aren't a lot of stoplights, but I'm proud of those numbers.

Thank you guys for your replies, hopefully a few more people will chime in with similar numbers. I know I could probably get better mileage if I drove a little bit slower, but with only two lanes each direction, I'd rather not become a hazard... Plus, we can't be giving our cars the reputation that they can't get up the hills. Other drivers can guage speed... but as of yet, they can't see our dashboards. :wink:
 

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MPG issues

Hi Geckoinsurance,
I have a 2004 5-speed, do mostly steady speed highway driving and average 65-66 MPG in winter and 70-74 MPG in spring-summer driving
at 62-68 MPH. I do have my tire pressure at 45 lbs. front and 44 lbs. back. I don't normally draft big trucks, just drive fairly normally; accelerate with assist and anticipate when I de-cellerate. My lifetime MPG average is 70.
:eek:
Ed
 

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I have done that route and others in and around the area (like sedona) and at that speeds, no drafting I get 55-85mpg and up when going down hill. Rick doesn't get that, cuz he never feathers into LB, he holds throttle to maintain. My best run was from flagstaff to phoenix, drafting doinf 85 mph and I got 86.2 mpg for the seg from there to my home in Buckeye. Only the last 18 miles were not drafting. It was a car transporter with REALLY low trailer and a flatnose truck. I got pics of it on my celly!

But straight high speed FE, there is a really nice power nook hidden at 80-85 mph (3200-3500rpm). If you feather the throttle back into LB and roll into it just right you can hold 70-75 mpg until you purge (Which happens very often at that speed.)
 

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Discussion Starter #8
Subterfuge, thanks for the reply... Next time you make a trip up 'north,' maybe you could drop by and give me some mileage pointers. Heck, you could even have another chance to drive a turbo'd Insight (I can't wait for May to roll around!). [I'm calling it a gift to myself for finishing freshman year in college...]

I've definitely noticed the 'nook' you're talking about... but as of yet... I'm not one to set the upper speed limit on the interstates. I can hold 80 without regret, but pushing it up into the 85 range is pushing it, at least until I decide to splurge and pick up an escort 8500 x50. Driving from Flagstaff to Holbrook I have found myself going 88 a few times without noticing a throttle increase, which would explain the power band around 3200 in 5th.

I know drafting would definitely increase the numbers, but how close do you get to the vehicles before you consider it drafting? My only concern there is that I don't want to make the semi drivers mad, I don't know what goes through their head when little red cars (blue in your case) pull up and disappear. I know they watch their mirrors, but I would think they would occasionally get agitated.

Thanks for the replies. It is interesting to see some "real world" numbers without having to baby the throttle too much or hold up traffic. Definitely not to discredit hypermilers! Speed vs. FE is sometimes a hard call, but 55 in a 75 zone isn't an option for me.
 

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Drafting

Hi Gecko,
Before I got into the turbo Insights I had my '00 5 spd with a life time mpg of 72.2, I believe. Above 80 mph I'd get 55 mpg, maybe a little higher. With the turbo and custom exhaust I can do around 64.1 mpg a little above 80 mph. Have you tried manually calculating you mileage and matching it against the vehicles mpg?

For drafting I take Willie's advise, make sure the guy driving the truck can see you. Flat beds or fuel trucks are excellent for drafting. They can see you ok and you get a good draft. Not too close where the turbulance is, further back where the air calms. If I'm really trying to keep the drafting distance steady I'll lower the sun visor till it just "touches" the "top" of the truck. Makes for a quick vertical "rifle sight".
 

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Discussion Starter #10
Jack,

I try to do a quick check on my mileage (manually) every time I fill the tank. It is usually pretty close, but consistently a little bit optimistic. Not a lot, but probably between 0.5 and 1.5 high.

Thanks for the tips drafting. I will see if I can try that the next time I get on the freeway (when the trucks are going approximately the speed limit. The interstate closest to here is pretty extreme with 6% grades one after another... so they range from 45 to 75 mph. I am happy to see your figures at speed before and after the turbo. Of course, these will depend entirely if you are driving consistently before and after. Or, I guess you could say by using the turbo to your advantage when necessary, but not taking it for granted and punching the throttle everywhere you drive... I hear that people with power tend to use it.

I am planning on getting a local shop to install the turbo and exhaust at the same time. When I asked him about some of the fabrication, he knows a guy in Phoenix who specializes in Garrett turbos and will do that aspect of it... It sounds good to me. This isn't the turbo thread though. ;)
Thanks for all of your help.

If anyone else has any stories / figures regarding "high speed mileage," please post a reply!

By the way, my tires are "Honda Recommended" pressures because the guy at Big-O freaked out when he did his routine pressure check... What percentage gain is there in increasing the tires by 10# (to 45)?

- David
 

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GeckoInsurance said:
I have found myself going 88 a few times without noticing a throttle increase, which would explain the power band around 3200 in 5th.
.

I allways found the interstate driving. 86mph was a smooth powerband for the engine. Not much IMA was needed and I'd net about 50-53mpgs.
 
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