55 MPG at 70-80 miles/hour

 

I get about 52mpg at 75-80mph, but that was on winter tires and I have a smashed underbody panel behind my bumper that is sort of missing.

 

Curious... What part of the east coast are you on? I'm knocking down around 55 MPG at 70 MPH on my trips to and through the Carolinas, going a little slower yields up to 10 mpg higher, but still haven't hit 70 MPG yet over longer stretches. The hilly terrain makes it rather difficult to maintain lean burn for me. Wondering if the area you're in is flatter, which would make it easier to maintain that?

____________________________
2000 Honda Insight, 277,XXX miles

 

On the contrary, you can have fun with lean burn if you modulate the throttle just right and aren't afraid to downshift to 3rd for going up a hill, and want to use lean-burn and momentum to bleed off uphill speed as slowly as possible. Coming downhill, depending on grade, lean-burn in fifth should be a foregone conclusion, unless you're braking.

 

YMMV between Insights. A high-speed 75mpg drive will bring MPG down to mid to low fifties, vs. 65-70 for going the same route at 55mph.

 

On 70 mile trips averaging 59 mph (most of it around 70-80) I will get about 70 mpg.

That sounds about right for an Insight with OEM tires that's not being hypermiled.

I recently drove 5,000 miles through Europe with my wife and our luggage for an 8-week road trip (i.e., our car was probably at the maximum gross vehicle weight). My Insight has all its aero panels intact. It has been driven only ~50,000 miles, so its engine should be in great condition. I have OEM tires overinflated a bit to 44F/41R. Most of the driving was at highway speeds of 110-120 kph (68-75 mph), with the A/C on for maybe 10% of the distance, and with headwinds and/or rain for probably 10% of the distance. I always use cruise control on the highway which isn't the most economical way to drive. I also use MIMA set to maximum assist and regen so that my car is able to climb moderate inclines in 5th gear without downshifting while regenerating in lean burn mode on declines. This results in very aggressive assist and regen which some claim reduces fuel efficiency. It could not hurt fuel efficiency very much because I averaged 68 mpg of very expensive European gasoline over 5,000 miles.

 

Most of the driving was at highway speeds of 110-120 kph (68-75 mph), with the A/C on for maybe 10% of the ....... because I averaged 68 mpg of very expensive European gasoline over 5,000 miles.

Art, that works out at approx. 3.4 l/100km !!!!! That is fantastic for that speed!
Or were you quoting in Imperial gallons? i.e. 68 mpg Imp = 56 mpg US or 4.2 l/100km ??
Sorry to cast a doubt, but I get approx 3.8-3.9 l/100 at speeds of around 120 kph on the autobahn. (2 light people, no luggage). This works out at 62 US and compares with figures quoted earlier in this thread.

This rises to 5.5 l/100 (43 US) if I keep around 140-150 kph (90 mph). But I don't do this very often.

Servus,
David

 

a non sequitur:

3rd gen Prius gets 39-40 mpg at 80mph.
45-47 mpg at 70-75mph.
This all in 80 deg F weather in slight rolling hills for parts of it, some flat land.

I've experienced this over 120 mile segment from Olympia to Portland.

 

I managed 71.9 mpg from shreveport LA to orange beach AL at 65-80 over 687.1 miles. You can do it but you have to be ready to exceed the limit at the very edge of lean burn down hill and then bleed the speed until you need assist over the next one. I dont think you could do this on flat level ground, but the south east US works quite well.

 

Silver Space:

I think you'll see varying answers that vary with weather conditions and terrain.

With good weather, no wind, night time and little traffic, I ran about 65 mpg or so running 70-80 mph from CT to PA on hilly/mountainous terrain. About 425 miles.

 

I commute 88 miles each way (with 70 of the 88 miles being highway) to work at speeds of 70-90+ MPH (of course, being in the SE, i have A/C running most of the time), modest hilly terrain, on an automatic transmission, with no underbody splash guards.

I have been doing this commute 5 days a week for 3 years and never have been above 50 MPG. My life time average (with 140K miles on the odometer is 45 MPG). I typically get 45-48 MPG.

Are all these 50+ MPG done on a manual or automatic transmissions, with AC running or not? I would expect these higher MPG to be on manual transmissions.

 

I drive 65-75mph 90% of the time and have a lifetime mileage of 61.1mpg.

 

I usually drive 70-75mph on flat roads(speed limit is 70 on the highway I commute on) and I get about 65mpg average.

I never thought I would ever want the speed limit to be lower but this hybrid does weird things to the way you think about driving.

 

Avg 53 MPG @ 80 mph with AC on MAX entire time.

 

These are all pretty difficult numbers for me to digest. I've only had my 06 for about 9 months now and don't get nearly those kind of numbers. When I bought the car it's lifetime was 50mpg. I'm running non oem knock off tires, with all the lower panels intact. I'm burning California gas, which I suspect to be worse than average. I'm lucky if I can maintain a 55mpg average.
My lean burn doesn't come on until I drop to about 58, and drops off at 60 or 60mph. I have a hard time maintaining speed and lean burn in 5th gear on flat roads, it just loses speed without the torque to keep it moving.
If I drive below 58, down to 54 or 55, I can stay in lean burn and see 75-85 in the FCD.
One of my problems is that on my way to work, I'm always in a rush, and drive 65-75mph, over the 20 miles. Plus there are a number on freeway interchanges, 1 bridge to cross, and a lot of exercising of the pedal. On the way home at 2am, when there aren't so many cars on the road, I can drive slower and get the mpg up. I'm looking forward to having the IMAC&C to help balance the exercising of the battery, and use gradual assist with less regen. It bites when I start my commute home, and spend half of the time in regen so I can get into lean burn.
Don

 

The tires are what's killing you. I have never seen a report where the best tire vs the Re92's was still within 5mpg. Those knockoff tires are probably draining you 8-15mpg.

 

Balto- Thats nice to hear. I just bought set of RE-92's, but can't justify installing them until these knock offs have worn down. Thanks

 

How much tread is left? You might be able to swap them then get the knockoffs on Craigslist.

 

They were new when I bought the car 9 months ago. They're not even good knock offs. Theyre made by some company called Enduro, and sold by Les Schwab. I'm not ready to throw them away yet, and don't think they'd have much value on Craigslist. I just thought that I could mount the RE92's on another set of rims, and run the knock offs in the winter. They do perform decently at 50 psi. At 60psi, I was getting a headache. The bridge I drive over has grooves in the concrete running perpendicular to the direction of travel. It creates an enormous hum

 

The front tires probably have more effect on fuel efficiency because they propel the car and support most of the car's weight. So you could run RE92's on the front and keep your current tires on the rear. However, the rear tires do very little, so they would probably outlast your RE92's. But in the meantime, you'd probably save some money on fuel costs, and your RE92's wouldn't age so much in storage.

 

Interesting reports in here.

My average (better in summer, worse in winter) is 70mph and 70mpg with mild hills, between Portland Oregon and Seattle Washington. I downshift into 3rd when I hit a hill that will drop me below 60mph. On the other side, I may hit 80mph coasting without regen, in 5th. I run my RE92 tires at 50psi. I have the stock panels under the engine compartment. I often run at the max speed that I can sustain lean burn - it only drops out when it goes to purge the system. I rarely use air conditioning.

My best trip has been ~85mpg going ~65mph in summer, not drafting. My worst 62mpg on a dark, rainy, winter trip with 4-500 lbs of iron car parts in the hatch. We are stuck with E10 fuel year-round, but I haven't tested any stations or fillups to find the actual ethanol content.

Both my Citrus and previous silver car performs about the same.

 

I dunno man, 70mph and 70mpg is going to be pretty hard for a lot of people to believe, myself included. You just have to be too far into the throttle at those speeds, the lean burn window is razor thin and almost impossible to hold; the slightest hill will kick you out. It is impossible to keep lean burn once VTEC engages at ~73mph in 5th gear. But I will concede its possible under good to ideal conditions. That's where we flub a lot of people up with our high numbers though, almost nobody drives in ideal conditions. I still get calls from new Insight owners all the time who do not understand why they can't get 70-80mpg.

It is highly likely that your average speed was very much below 70mph, even if you occasionally did cruise at 70mph. Use your GPS to be sure. I've always said that mpg numbers are pretty useless without average speed, especially in the Insight.

Going 70-80MPH, averaging ~60-65mph over long distances, I'll get 50-55MPG, occasionally hitting ~60mpg in good conditions. Most people don't realize how slow their average speed is. Hills, construction zones, towns, slow drivers in the left lane and the occasional small animal all conspire to lower your average speed precipitously. It takes a surprising amount of effort to maintain an average speed of over 60MPH. Try it some day.

 

I dunno man, 70mph and 70mpg is going to be pretty hard for a lot of people to believe, myself included. You just have to be too far into the throttle at those speeds, the lean burn window is razor thin and almost impossible to hold; the slightest hill will kick you out. It is impossible to keep lean burn once VTEC engages at ~73mph in 5th gear.

It is highly likely that your average speed was very much below 70mph, even if you occasionally did cruise at 70mph. Use your GPS to be sure. I've always said that mpg numbers are pretty useless without average speed, especially in the Insight.

Going 70-80MPH, averaging ~60-65mph, I'll get 50-55MPG in my Insights. Most people don't realize how slow their average speed is. Hills, construction zones, towns, slow drivers in the left lane and the occasional small animal all conspire to lower your average speed precipitously.

I use GPS on every trip - even to verify traffic routes to and from work every day - all of 9-miles. On a northern trip, I reset the trip when I leave Vancouver (often stop by my parents' place), visit in Federal Way for a few days, and look at the reading when I make it back to the Oregon border. Even with a few miles of suburban driving at 40-45mph, I get back to the Oregon border with very close to a 70mph average, depending on the specific trip. Now this is on the FCD - there is no good way to measure without doing a tankfull that you know was measured correctly at the pump(s), but these are its numbers. I have no problem maintaining lean burn on the trip, with the exception of two hills and the purge cycles, between Vancouver, WA and Federal Way, WA. I drive outside of high-traffic hours - 8-10AM, or in the 8PM-1AM range. I get cat purges every couple minutes in summer, but they seem to occur far less frequently in cooler months. I have no idea what controls them.

In my other (modified) vehicle, I have direct ECU access to datalog the flow of my fuel injectors and trusted that accuracy more than I do the Insight's.

I was hoping for a bit more speed with lean burn after I replaced a missing under-engine panel and taped up the wheel strakes, but nothing improved. I doubt I'll get an improvement after replacing my oil-soaked air filter either. I'm curious about the fabricated aluminum under-engine panels available now - anything we can do to smooth the airflow should help. I'd like to see 75mph at 70mpg.

FYI, I "can" drive from Beaverton, OR to Vancouver, WA, and back with well over 80mpg. I think I hit 87mpg once. This was at normal speeds in spring - 55-60mph highway, and about 2 miles of 35mph suburban driving in 3rd gear. This was outside of peak traffic on a holiday weekend. If I can't simply feather the throttle for a long time, I spend much more time at WOT. I typically average only 55-60mpg per tank, mostly because of my 9-mile 40-minute morning commute, and 30-minutes in the evening.

70mph at 70mpg is certainly possible for any 2000 model, without even trying to do anything but maintain the thin line of lean burn at the ~75mpg display mark. Also I'm sure many know, but the display will go down one tick further in cooler months with either cooler weather, or winter fuel blend. Lean burn can be maintained at higher speeds, but it returns a couple mpg less. In winter, the same Federal Way trip often requires 65mph to hit 70mpg. If I have a headwind (rare), 65mpg will be difficult to maintain. I think I once hit ~60mpg at 55mph, in a storm with thick water on the road, and a ton of cross-wind. Same I-5 route!

/endofdigression

 

Yeah, I guess I should have known that you would use your GPS. I will also concede that you maintain your Insights in better condition than I do. I always forget that Insight #3 is missing underbody panels, which I'm sure produces a hit, especially at the higher speeds - and it is the one I was thinking of, when mentioning those numbers.

It is always interesting to see the variation. I guess I've just gotten out of the habit of touting the ultra high numbers; talking with so many people, it is evident that it is frustrating, as most people just don't have the skill and/or commutes to be able to pull them.

I still can't help but mention my 92.4mpg trip in the 440,000 mile Insight(at the time) occasionally, though. At an average speed of 49mph... through the mountains of Colorado.

I need a nice low mileage Insight, all of mine are high mileage and/or beat to hell lol.

 

I still can't help but mention my 92.4mpg trip in the 440,000 mile Insight(at the time) occasionally, though. At an average speed of 49mph... through the mountains of Colorado.

Yeah, I don't have the patience for that. I mostly want the highest speed that I can maintain while in lean burn. I did not see a difference with simply folding my passenger side mirror in

I swear that on some long roads with a 45mph speed limit, the car reports insane economy (>100) in 4th or 5th gear, but on others, I have to dip into 3rd to get a reasonable number, and not use assist. The first is in Washington, with their better kept, smoother roads. The latter is here in Oregon, and very rough. 10 miles of even elevation, both going East/West, and typically no wind, but there is a huge difference, consistently. I have never been able to figure out the cause. I'm only out in those locations a few times a year though.

 

I'm located in San Diego, CA and do a 55 mile commute one way traveling at night for work when it's cooler doing about 65-75 mph and average anywhere from 67-72 mpg. This is also factoring in all the hills we have as well.