My favourite road.
 

Today I came along my favourite bit of road. The B925 from the Berverkae Roundabout (Mossmorran), through Auchtertool to Kirkcaldy. Before starting I reset my Current Trip details in my ScanGauge E, and the 6.3 miles was completed at an indicated 107 mpg (UK)/89 mpg (US). It is a brilliant road. Several short sharp inclines, three reasonably long declines, and some variable country road in between. I use this piece of road on my way home, whenever possible. I will happily add extra miles to my journey to get on that road.

HeHe, my favorite is Crafford rd, about 5 miles from my home. Usually deserted since it has some fearful history that scares a lot of people away. Supposedly someone hung themselves from the railroad overpass. Very narrow opening you have to pass through almost praying there is no one coming in the other direction. I hit 120 US if I start from the beginning of the road at speed. Best I ever did for 45 miles with some other serious hypermilers was 72.8. IN both cases there are downhill sections that allow EOC for a mile or very close to that.

Without EOC you will never get to those numbers. It takes 5 miles for my engine to warm up many times, Driven normally that would be about 1-1.5 miles to full operating (thermostat open) temperature.

If you haven't tried some Chevron Techron fuel injection cleaner. I get it at Costco for $3.33 a bottle for 6 bottles. It killed the "rolling misfire-lean" CEL in the Echo.

Not sure what is the equivalent in your neck of the woods, but it sure has been a super effective treatment for a few cars for me. One CEL and one that just died at idle, running on 3 cylinders.

The fairly sharp inclines followed by gradual downhill sections that allow extended coasting really bump up the MPGs.

You can buy Techron fuel injection cleaner here, but it costs $22.15/ bottle. I used Redex Petrol Treatment, but there was no difference afterwards. However as I didn't have any issues before using it I didn't expect much.
I don't do EOC. My power steering is very heavy, and on the piece of road in question I am normally in DFCO mode on the down grades. Just one long section, at the end, where I stick it in neutral.

To join the UK drivers, my favorite drive is Route 203 (& farm roads) southeast of Everett, Washington, USA. I love to play English composer Ralph Vaughn Williams' tone poems, which describe the English countryside so intimately, & deeply. Driving either cars, motorcycle or bicycle, I feel like I'm in English landscapes.... tho I have never been there. Surrounding Route 203, travels to the Salish Sea(Puget Sound) can be made, or go to the deep moss-filled Cascade Mountains, Mt. Rainer or travel further to desert-like eastern Washington.

A bit too flat and straight for my liking but nice part of the country.

Good you know about the region. Nuthin' wrong wit' flat..... lots of bottom land wildlife recreation regions to walk & explore (like I said, Vaughn Williams tone poems). Really flat is when the rivers are in major flood mode. Then, its like three 20mile long lakes radiating from one point. AND THIS YEAR, the fall colors were the best of the last 43 years.... probably last 50 or 60 years!
Of course, if ya gots ta get away from flat, there is 3000 foot Snoqualmie Pass, 4000+ foot Stevens Pass, 5500 foot Chinook Pass, 5500 Washington Pass, 6400 foot Lion Rock or some 7000 foot mountain logging road crawls. Ya ain't got them in England.

The highest road here in Scotland is only 2198 feet, but it is a pretty boring climb. Much better is Bealach na Bà, Gaelic for Pass of the Cattle, at 2054 ft.
Image by Stefan Krause, Germany - Own work, FAL, https://commons.wikimedia.org/w/inde...curid=15765099

Personally, I am happy with some gently undulations such as we have here in the south of Scotland.

When you know the road you can "roller coaster" it and get some fabulous MPG. I heard of someone coming down the eastern slope of the Rockies where they coasted for 35 miles. I remember one valley in either California or just across the border east of California, where you could see the headlights 40 miles away and it took 30 minutes for them to meet at 80 MPH (pre energy crisis speed limits). Road was perfectly straight.

Not wanting to spoil a good story, but the furthest you can see on a level, straight road (with an eye level 5 ft 7 above the ground) is 12.2 miles. To see 80 miles you would have to be about 4400 ft above the target.

40 miles total with mountains at either end straight and level all the rest of the way. We drove from LA to Memphis Tennessee straight through, gas was $.0329 a gallon. Thinking about it (1973) at 80 it would take 15 minutes to meet in the middle on a 40 mile stretch. Closing speed would be 160 mph so 40 miles in 15 minutes not 30. The air in LA was a brownish yellow with smog in 1973. Traffic was light so it was easy to pick out one vehicle and monitor it until we passed each other probably 2 AM. out in the desert it was clear.

I stand corrected on the math. 30 minutes at 80 is 40 miles. 15 at 160.