Car with best MPG at 90mph

I have a 180 mile commute each day on a deserted highway. And before you start lecturing me, stop. I plan to drive 90mph because I value my time, I work 12 hours a day, and with 2 hours of commute every minute saved is worth it. Plain and simple I am not interested in hearing your opinion about how much gas I would save if I slowed down.

I am only interested in which car will give me the highest MPG at 90mph. Right now I am driving a prius which is returning 36mpg at these speeds. It's not the ideal car as there is a slight grade I have to climb the entire way which depletes the hybrid battery quickly and then it is all up to the little 1.5L. Would a TDI serve me better? I'm not very interested in paying for maintenance over what I save in gas. Suggestions? 

Sounds like the perfect commute for a Model S. 

Other than that, you want something as aerodynamic as possible, ignore anything designed for the city and go back to the old days with low rooflines, tall gearing and small frontal area. 

That or an insight. 

+1 on the model S

In reply to twowheeled :

What is your goal mpg? 

Would you be willing to do some modifications or are you looking for a plug and play option? 

I agree with Tom that aero is going to be key. 36mpg sounds pretty good to me at those speeds and from my understanding the Prius is pretty slippery. Could a small turbo help the Prius get up the grade?

http://www.aerocivic.com/

Doing this makes things a little bit ugly, but every bit of reduced drag helps a lot at those speeds.  Before swapping to one of the lean burn Honda engines the guy was claiming 50 mpg at 90 mph.  If that's reproducible, it's pretty damn good. 

If not an S, I would think that the Volt may be the best bet. First 15-40 miles each way (any real world data at 90mph?) would be gas free, after that probably 30mpg. Guessing. 

That only works if you have a place to charge it at work though. 

If you can plug in at work maybe adding another battery pack to your existing Prius and getting a plug in hybrid kit for it would be the way to go.

From my experience you're probably best avoiding anything with a turbo. 90 mph in my MS3 is getting close to boost. Mileage drops off fast at that point.

Something that's slippery and has a motor that doesn't mind running higher in the rev range should serve you well. While I have no experience with anything from Tesla I know a Leaf loses power fast on a highway. Like 20% of its estimated mileage disappears. 

The current gen Mazda 3 sedan has a .26 CD, and should do pretty well with the high compression 2.0.  

If you really value your time, live closer to work. I love cars, love driving - but cannot fathom any job worth a 2 hour commute.

Based on your username- motorcycle?  Any sport touring bike will eat that commute up, many with over 40mpg to boot.

Barring that, I think you may be onto something with the TDI- I wonder if you could play with gearing to try to get the most efficient 90mph cruising speed.  I think the problem for many cars is that 90 is above what they're really geared for, so fuel economy will fall off quickly.

My old M3 could only get as bad as 9 mpg close to redline in third gear, at 145 it still got low teens.  At 90 it offered about 30 mpg, so an E30 M3 is out.  This was in a controlled environment (US 31 N.) using the trip computer.

From searching online because I couldn't sleep at all, it sounds like an older tdi (99-02) with a 5th gear swap and some aero work can put up mpg figures in the 50s at 85-95mph.

I found that in a thread on here, but also a lot of euro forums say the same thing.

 There's got to be something newer that is similar though. 

It does seem like lots of people wanted the prius for the mileage you are getting currently, so more might be harder to come by. 

At 90 mph, aero drag is the #1 contributor, by a pretty wide margin.  And with the grade, weight sucks as well.  Third, likely, will be gearing and engine drag.

It may suck, but I bet it would be near impossible to beat the Prius at 36mpg- that's pretty remarkable at that speed.

alfadriver said:

At 90 mph, aero drag is the #1 contributor, by a pretty wide margin.  And with the grade, weight sucks as well.  Third, likely, will be gearing and engine drag.

It may suck, but I bet it would be near impossible to beat the Prius at 36mpg- that's pretty remarkable at that speed.

AlfaDriver has it right in terms of the order of loads.

The approximate drag force on a Prius at 90mph is ~130 pounds. Reduced frontal area or reduced Cd are the directions you need to pursue. The two together (Cd*FrontalArea) will give you a very good idea of the mileage result. The Cd and area can be found fairly easily on the internet.  Like here: Cd*A listing

As I pointed to over in this thread the Torque App and Prius Software can give you an easy way to see the health of the hybrid pack.  I say that because you are mentioning the deletion of the battery on grade.  I live where there are no grades but I still wonder if this is normal and the software could tell you.  

I presume your 180 miles is 90 each way.  But, at this rate you are still looking at 45+k per year on the vehicle.  My personal experience with Prius ownership is that maint and consumables are cheap.  I would go to genuine Toyota oil filters and drag the changes out to 10k miles. This is still a change every 3 months.  

Tires are cheap. You can get tires with 80k ratings that will run $350 per set of 4, mounted.  That means about a new set every 1.5 years or an annual cost of about $233 for tires which is cheap. Sample on tires   Brakes last 100k or more.  

I'm not sure what year you have but at 1.5L it is a Gen2 version.  Odd fact, 2004 and 2005 Prius has odometer software that only goes to 300k miles and then reads no higher.  Following years continue to read higher.  Many, many go that far.  

¯\_(ツ)_/¯ said:

Based on your username- motorcycle?  Any sport touring bike will eat that commute up, many with over 40mpg to boot.

Barring that, I think you may be onto something with the TDI- I wonder if you could play with gearing to try to get the most efficient 90mph cruising speed.  I think the problem for many cars is that 90 is above what they're really geared for, so fuel economy will fall off quickly.

And tires that don't last nearly as long, sprockets/chain to replace, etc. 

The mpg is far outweighed by the other consumables.

Based on your post, get an Audi. Doesn't matter which one. Second place, Mercedes. 

szeis4cookie said:

If you really value your time, live closer to work. I love cars, love driving - but cannot fathom any job worth a 2 hour commute.

Many reasons to commute-that far,  maybe a spouse’s job, maybe friends, family, neighborhood, etc. 

Selling a house will cost you 10% of selling price when you add moving costs, selling costs, and required acquisitions for your new place.  That’s $30,000 on a $300,000 dollar home.  

A lease may cost you thousands  to break, more than enough to justify the commute. Or the cost of living closer is too high.  

szeis4cookie said:

If you really value your time, live closer to work. I love cars, love driving - but cannot fathom any job worth a 2 hour commute.

This is the actual right answer, although you don't want to hear it. Have you figured out how much commuting that far costs you? Fuel, maintenance, tons of miles on your vehicle and that's not even valuing your time. You could probably take a lower paying job that was closer to home and come out ahead financially As well as having more time/improved quality of life.

I'd think from the TDI standpoint you'd have to stick with the 99-03 ALH engine cars, the newer ones get noticably worse MPG to the order of 3-4mpg. I went from an 03 ALH to an 05 BEW engine code and have seen that consistently at any speed.

Unfortunately my commute is more city roads instead of highway these days so I'm not able to test at the speed you mention but I do typically avg 70-75mph road type aside.

It's worth noting the previous jetta was on much larger all terrain tires for the 2nd half of my ownership and still ticked over 40mpg mostly. which even correcting for rollout still gave me a noticable mpg hit from it's more stock existence where I normally averaged high 40's. The current jetta wagon is on low rolling resistance doughnuts and still cannot match the mpg of the older one on all terrains.

I'd think with a euro 5th gear swap on LRR tires you should be able to beat the prius MPG, but fuel costs and any additional maintenance (fuel filters every 20k) might make it a wash?

Funk it. 

I hope you don't hit someone driving those speeds because you think minutes matter when you live so far from your job. I hate sharing the road with people that think this way. 

stafford1500 said:

alfadriver said:

At 90 mph, aero drag is the #1 contributor, by a pretty wide margin.  And with the grade, weight sucks as well.  Third, likely, will be gearing and engine drag.

It may suck, but I bet it would be near impossible to beat the Prius at 36mpg- that's pretty remarkable at that speed.

AlfaDriver has it right in terms of the order of loads.

The approximate drag force on a Prius at 90mph is ~130 pounds. Reduced frontal area or reduced Cd are the directions you need to pursue. The two together (Cd*FrontalArea) will give you a very good idea of the mileage result. The Cd and area can be found fairly easily on the internet.  Like here: Cd*A listing

 

An alternative to that listing is using the OEM data that was used for certification.  You can find that data here- https://www.epa.gov/compliance-and-fuel-economy-data/annual-certification-data-vehicles-and-engines

Choose a year, and the columns labeled Target Coeff, those are used to calculate the drag- A is just the base lb, B is a linear terms in lb/mph, and C is a non linear term of lb/mph^2.  So use 90mph and you will get a good number. 

For instance, a 2010 Prius has a Target A term of 20.234, B of 0.01993, and C of 0.01874, which calculates to 173lb at 90mph.  If you run a quick calculation of all the cars in 2010, the lowest drag at 90mph (with data, some don't have any) is the Hyundai Genesis Coupe at 165lb, but the next choice may be better- as it's 168lb, but about 600lb lighter- the Kia Forte.  Then a smaller Prius version at 169lb at 3375lb.  

There's a similar data set for fuel economy cert if you want to use that drag data.  But I know that site...  because.

In reply to alfadriver :

That data looks to include rolling resistance as well as the aero numbers I kicked out, and it is the targeted value from the manufacturer, so that is a more accurate set of numbers.

Alfa,  Please share the other dataset :)

Current Prius + aero mods seems like the best choice if you don't want to just move closer.