What factory car is the steady state, 65 mph, MPG champion?
 

I was reading the thread on replacing a VX with a G1 Insight and it got me thinking. What is the best car ever MPG wise at a steady 65 mph? One of the old TDI's or a newer Cruise diesel maybe? I'm talking a readily available production car in it's basic form, LRR tires aired up, a grill block and wheel covers, a custom tune, maybe an air dam, but not a total redesign, home build, or powertrain swap.

hmm, diesel Chevette? Ford Escort diesel? are two to pop in my head from my youth that were great, or would you want a gas engine?

Diesel is fair, I remember some recient reviews of the Cruise diesel where they got over 70 mpg at 55 over a long test in normal traffic. I wonder how much 65 mph hurts or a tune and a few mods might help those Car and Driver numbers. What are the best VW TDI guys with a few mods getting?

Easy.
Any electric car.
Even my unaerodynamic leaf does around 140 mpge at 65mph.

For a little while at least, I did ask mpg not mpge which IMO is not exactly apples to apples. I'd say a plug in hybrid is fair or something like the Volt if you weren't starting fully charged. Basically I want to drive 8 hours without stopping on the least amount of fuel.

At 65 mph, aerodynamics will have enough of an effect that I doubt anything would beat a 1st gen Honda insight.

However, for a non-routine trip, there are a few vehicles I would pick instead of a 1st gen insight.

Since you said miles per gallon, I'm assuming plug-in hybrids and electric cars do not count.

In that case the Gen 1 Honda Insight manual transmission would take the cake. It has one of the lowest drag-coefficients of any modern car, along with one of the most efficient engines. I have observed 70-80 MPG cruising at 65 MPH on the highway, if the wind isn't against me, in 40 F degree weather.

If you take into consideration plug-in hybrids and electric cars, then we're talking about miles per dollar, which is an entirely different scenario, since electricity costs are not directly related to gasoline costs in every area.

the Chevrolet Sprint in mid late 1980's had a few versions, & 1 was for economy, the normal model, & a Turbo version.

Honda also made a special version of the CRX in early years with better mileage.

this will be slightly off topic, but probably first you will hear of it, in early 1980's Dodge & Plymouth made a car called a Omni, or Horizon, nothing special, & everyone thinks about the 2.2 liter OHC engine, however!!! they also offered a gasoline Peugeot 4 cylinder 1.6 liter cam in block in those cars, very very rare, I have 1 I started parting out, but could snap pics of engine as drivetrain is still I it. it got 45-50 with a 4 speed, always wondered what it would have done with a 5 speed over drive & tweak engine for a hair more power.

My parents went down to the Dodge dealer in 1978 (I was 8) and bought a new Omni. Top of the line, but an automatic if I remember right. Much to my dismay as there was also a full boogie Aspen R/T 360 there for the same price, but the Omni was car of the year and going to save us big in the Carter malaise (actually my stepdad was a big fan of FWD in Montana's snowy winters his other car being a 75 Eldorado with FWD... and 500 cubic inches). It had a VW sourced 1.7 inline 4. I got to drive that car to Oregon and back 10 years later in 1988 and blew the head gasket with still under 100,000 miles on it. I think it was $300 to fix, and we sold it the next year for $800 still almost cherry with under 100,000 on it.

That's what I was wondering for an G1 Insight. But sounds like a bone stock diesel Cruze will do close. I suppose nobody is modding them up much yet being under warranty and all. EPA says the 2018 manual is 52 mpg highway vs the Insight at 59 mpg (under the current test, not the old test in the 2000's) Diesels often beat the EPA test though while the hybrids are optimized for it (or the test is optimized for hybrids). Then the problem now is diesel here is $3.09 a gallon and regular is $2.58/gal so a bunch of that would be lost in cost per mile.

Nothing beats the pure electric in cost per mile as pointed out especially here as we have about $0.06 per Kwh electricity. Just the range doesn't make them a good Montana highway car.