The DOJ Tesla probe has expanded to include EV driving ranges

[sleepydoc]

I am glad someone finally is bringing up that drag goes by the square of velocity.

It seems that a common speed among Tesla drivers is 80 mph, so I wish your table went up higher.

I very often see people say "I get nowhere near the EPA range on a simple trip on the Interstate even when cruising at a constant 80 mph". Geez.

Speed	Relative Drag
40 MPH	1
50	1.56
60	2.25
70	3.06
80	4.00

There you go! But yeah, everyone wants to go fast then get’s mad that they don’t get the range they want. It’s physics, folks, Ya can’t beat it! This is exactly why I sit in the right lane going slower no matter what car I’m driving unless getting there faster is important.

 

[David99]

Just a little perspective, though. Driving at 80 vs 40 doesn't mean your energy consumption is 4 times.

#1 driving twice the speed means half the time to drive any given distance. Hence divide total consumption by 2. (Edit: this is incorrect! See next post)
#2 drag isn't the only thing when driving. In fact, at 45 mpg, the energy needed for aero drag is about equal to all other things using energy (motor losses, rolling resistance, losses in electronics,...)

 

[mongo]

#1 driving twice the speed means half the time to drive any given distance. Hence divide total consumption by 2.

That's incorrect. You have 4x the aero force over the same distance, thst's 4x the work (energy).
You may be thinking of power * time. However, power is 2 times the four times because you are travelintwicecas far per unit time, so (ignoring the other loads) it's 8x the power to go 80 vs 40, but you are only traveling for half the time which brings it back to 4x the energy.

 

[David99]

That's incorrect. You have 4x the aero force over the same distance, thst's 4x the work (energy).
You may be thinking of power * time. However, power is 2 times the four times because you are travelintwicecas far per unit time, so (ignoring the other loads) it's 8x the power to go 80 vs 40, but you are only traveling for half the time which brings it back to 4x the energy.

Thanks. You are correct!

Looking at the graph (which is from Tesla) it shows that because the 'base consumption' is half of the total consumption at 45ish, and doesn't change much at 80, the total energy consumption per mile is still only twice at 80 vs 40.

 

[sleepydoc]

Thanks. You are correct!

Looking at the graph (which is from Tesla) it shows that because the 'base consumption' is half of the total consumption at 45ish, and doesn't change much at 80, the total energy consumption per mile is still only twice at 80 vs 40.

Yes, what I posted was solely for wind resistance, as the graph shows, total energy consumption comes from the car systems, the tires, the drivetrain, and wind resistance.

The car system consumption is trivial and the tire contribution is static. Above 50 MPH Wind resistance is the biggest contrIbutor.

The simplest way to think about it is at 50 MPH tires, drivetrain and wind are all equal. Above that, wind increases exponentially and drivetrain increases more or less linearly. Of course that only adds to the extra losses incurred by going faster So it’s another reason not to go faster than necessary. Estimating from the graph, total Wh/mi is 210, 250, 300 and 360 at 50, 60, 70 & 80 MPH respectively meaning total consumption at 80 MPH is 44% more than it is at 60 MPH.

 

[GBMaryland]

The number one thing that people fail to consider is the simple fact that no one worries what the range is for an ICE car. When was the last time you complained that your ICE car only got 15 MPG rather than the advertised 25 MPG? Pumping gasoline is still a much quicker way of transferring energy to a car than charging and there are over 115,000 gas stations compared to around 10,000 DC charging stations in the US meaning you virtually never worry about being able to fill up.

The Primary difference with an ICE vehicle is that it will almost always have a 400-450 mile range, which doesn’t actually change in any meaningful manner in cold weather.

In so far as gas mileage, once you lock down the actual mileage, it remains consistent. Obviously, the ICE manufacturers report best case numbers. Which I also see as criminal…

The whole speeding part of your commentary I don’t care about. If you want to speed, not a problem in my book.

 

[sleepydoc]

The Primary difference with an ICE vehicle is that it will almost always have a 400-450 mile range, which doesn’t actually change in any meaningful manner in cold weather.

In so far as gas mileage, once you lock down the actual mileage, it remains consistent. Obviously, the ICE manufacturers report best case numbers. Which I also see as criminal…

The whole speeding part of your commentary I don’t care about. If you want to speed, not a problem in my book.

Not exactly - wind resistance affects ICE vehicles, too, so they will also see a significant decrease in mileage going 80 mph. They have so many other inefficiencies that it’s less noticeable and like I said, no one perseverates on ICE range.

My comment on speed wasn’t concerning breaking the law, simply noting the waste.

 

[David99]

The Primary difference with an ICE vehicle is that it will almost always have a 400-450 mile range, which doesn’t actually change in any meaningful manner in cold weather.

Cold weather and winter driving conditions can significantly reduce fuel economy. Fuel economy tests show that, in city driving, a conventional gasoline car's gas mileage is roughly 15% lower at 20°F than it would be at 77°F. It can drop as much as 24% for short (3- to 4-mile) trips.

Fuel Economy in Cold Weather

Cold weather and winter driving conditions can significantly reduce fuel economy.

www.energy.gov

 

[zroger73]

Cold weather and winter driving conditions can significantly reduce fuel economy. Fuel economy tests show that, in city driving, a conventional gasoline car's gas mileage is roughly 15% lower at 20°F than it would be at 77°F. It can drop as much as 24% for short (3- to 4-mile) trips.

Fuel Economy in Cold Weather

Cold weather and winter driving conditions can significantly reduce fuel economy.

www.energy.gov

I've never noticed any signifiant decrease in fuel economy associated with cold temperatures in any of the dozens of ICEVs I've owned and I've got data to support that.

Here is a graph showing fuel economy for four years of fill-ups in my '19 MX-5 Miata. You can graph the fill-ups in the other vehicles I've tracked with Fuelly and you'll notice the same.

In fact, I've dispelled a lot of myths by logging this data such as:

• Fuel economy will increase after the engine breaks in
• Fuel economy will increase after each engine oil change
• Fuel economy will decrease during the Summer due to A/C use
• Fuel economy will change due to use of Summer/Winter gasoline formulations
• Fuel economy will increase if you use a higher octane than required

What does significantly change fuel economy is how hard I press the accelerator and brake pedals.

For my first nine months of ownership, I used 5% SoC during my 14-mile commute to work every day. Yesterday, my Model Y saw the coldest temperature since I took delivery - about 20ºF. I used 8% of the battery's SoC during the exact same commute. And, the battery's SoC decreased another 3% just sitting outside asleep at the office. When I got home yesterday evening, it took twice as much energy to reach my charging limit as it normally would.

This is not a problem for me because I don't normally drive more than 50 miles per day, but from what I observed based on actual experience, there was a major decrease in range in my EV due to cold weather compared to no significant difference in range in my ICEVs.

I still prefer EVs over ICEVs at this point and for my use case, but I think it's something that potential and recent EV buyers need to be aware of.

https://www.fuelly.com/car/mazda/mx-5_miata/2019/zroger73/963124/fuelchart

 

[sleepydoc]

I've never noticed any signifiant decrease in fuel economy associated with cold temperatures in any of the dozens of ICEVs I've owned and I've got data to support that.

With all due respect, someone in Texas can't make any stamen's about cold weather. The efficiency at Texas temps won't change much. In MN it absolutely does. The car runs richer when it's cold, engine oil is thicker, transmission oil is thicker. It's simple physics.

This excludes the fact that you need to warm up the car enough to get the windshield defrosted, you're drawing extra power to run the heated seats, etc.

• Fuel economy will increase after the engine breaks in

Agree - current engines and tolerances are such that there's no functional difference

• Fuel economy will increase after each engine oil change

Also agree - if there's that much difference in your oil you're waiting far too long to change it!

• Fuel economy will decrease during the Summer due to A/C use

This is absolutely true. The A/C uses power, either from the alternator or being directly driven off of the drive shaft. There is no such thing as a free lunch and it will affect your economy. The asterisk comes in when you compare running the A/C to other options like opening the widows. Depending on the speed, open windows increase drag and can have a larger effect on your economy than running the A/C.

• Fuel economy will change due to use of Summer/Winter gasoline formulations

This is also true - In Minnesota they blend ethanol in higher concentrations in the winter. Ethanol has a lower energy density. Diesel also has anti gelling additives that can affect efficiency.

• Fuel economy will increase if you use a higher octane than required

Yes - Assuming your car doesn't need a higher octane to prevent predetonation there is zero benefit to paying extra for high octane fuel.

What does significantly change fuel economy is how hard I press the accelerator and brake pedals.

Ironically, this causes less of a difference in EVs than it does in ICE cars!

 

[MP3Mike]

It is looking like the law suits related to this are likely close to being dismissed. Tesla rebutted with the fact that they are required to only advertise the EPA sanctioned/approved range, so they can't be sued for doing that. (And that states are not allowed to make laws/regulations requiring a disclosures different than the EPA rated range.) The Plaintiff basically agreed and then tried to pivot to suing based on the range estimated displayed on the screen in the car not matching reality. (The estimate is based on the EPA range, so again Tesla said they can't be sued based on that.)

So it should be up to the judge pretty soon, I assume the DOJ will have to come to the same conclusion. You can't sue Tesla for advertising an estimated range when they are following the EPA rules.

 

[Gloff]

Yes - Assuming your car doesn't need a higher octane to prevent predetonation there is zero benefit to paying extra for high octane fuel.

Depends on the engine. Most ICE cars on sale today have some variation of intake timing (VTEC, TI-VCT, VANOS, VVT-i, etc). Higher octane allows the ECU to advance the timing without detonation, increasing power and fuel economy.

 

[stopcrazypp]

It is looking like the law suits related to this are likely close to being dismissed. Tesla rebutted with the fact that they are required to only advertise the EPA sanctioned/approved range, so they can't be sued for doing that. (And that states are not allowed to make laws/regulations requiring a disclosures different than the EPA rated range.) The Plaintiff basically agreed and then tried to pivot to suing based on the range estimated displayed on the screen in the car not matching reality. (The estimate is based on the EPA range, so again Tesla said they can't be sued based on that.)

So it should be up to the judge pretty soon, I assume the DOJ will have to come to the same conclusion. You can't sue Tesla for advertising an estimated range when they are following the EPA rules.

I missed this thread, but the OP tried to make similar claims (that the car doesn't get the EPA combined range when driving in conditions that are completely different from the EPA combined cycle). Manufacturers are not liable for this. The cases where manufacturers lose is when EPA confirmation testing can't replicate the test results. So far that have not been the case with Teslas.

A lot of people (including journalists and perhaps the DOJ) don't seem to get the difference though. They bring up media tests (like the CR test) which are typically done at 70mph. If the federal government wanted advertised range of EVs to replicate 70 mph driving, they should change the test methods to reflect that.

 

[zroger73]

Depends on the engine. Most ICE cars on sale today have some variation of intake timing (VTEC, TI-VCT, VANOS, VVT-i, etc). Higher octane allows the ECU to advance the timing without detonation, increasing power and fuel economy.

...if the ECU is tuned to take advantage of higher octane fuel.

Take Honda's 3.5L V6, for example.

In Honda applications, this engine develops 280 HP using regular gasoline.
In Acura applications, this engine develops 290 HP using premium gasoline.

However, using premium in a Honda won't get you 290 HP. Using regular in an Acura will get you less than 290 HP, though.

 

[Dracaris]

When we're on road trips the battery has a longer range than my butt, so we stop whenever we want - especially if there's a Buc-ees. Ha!

 

[David99]

They bring up media tests (like the CR test) which are typically done at 70mph. If the federal government wanted advertised range of EVs to replicate 70 mph driving, they should change the test methods to reflect that.

That's fair. OTOH, the issue wasn't that CR's test showed all EVs get less real world range than advertised (based on the EPA guidelines). Rather, it exposed that Tesla vehicles get far less real world range compared to every other car in respect to their advertised numbers. The takeaway from their test was: if all EVs are tested equally, why are Tesla's number so much more inflated?

This isn't a new finding. I've been trying to find some info on this and didn't get far. Part of the issue seems that the majority of car manufacturers self report. Basically they just tell the EPA. Part of the issue is it isn't just one test. As far as I understand, the manufacturer has some freedom on the different test cycles. I'm not an expert, but it seems to me that entire process was designed to leave enough 'wiggle room' and ambiguity in favor of the manufacturer.

Fact is, when you drive a Tesla at the EPA rated consumption, you won't be able to get rated range. That has been the case with all my 3 Tesla vehicles.

 

[MP3Mike]

The takeaway from their test was: if all EVs are tested equally, why are Tesla's number so much more inflated?

But they aren't all tested the same way. There are at least two different EPA approved methods for testing vehicles. (And then an OEM can choose to de-rate the range they received in the test if they want to.)

 

[3sr+buyer]

Fact is, when you drive a Tesla at the EPA rated consumption, you won't be able to get rated range. That has been the case with all my 3 Tesla vehicles.

When not carrying stuff on the roof rack, I usually get better than the EPA rating in normal commuting (lots of highway, but often traffic limited to 40-60mph). Granted, this differs from the forum-typical 80+mph highway driving or flooring the pedals often, but it is real world results.

 

[David99]

But they aren't all tested the same way. There are at least two different EPA approved methods for testing vehicles.

I am aware of that. Why wouldn't a car manufacturer use the method that gives them the highest range number? I believe the answer isn't that everyone picks the worse test combination while Tesla picks the best. I believe, based on my experience, they are cheating somehow. If the EPA test energy consumption doesn't add up to the range, something is fishy.

 

[mongo]

I am aware of that. Why wouldn't a car manufacturer use the method that gives them the highest range number? I believe the answer isn't that everyone picks the worse test combination while Tesla picks the best. I believe, based on my experience, they are cheating somehow. If the EPA test energy consumption doesn't add up to the range, something is fishy.

The more efficient the vehicle is (lower Wh/mile), the greater the range impact will be when increasing the drive load due to increased speed, using a reduced regen setting, or unfavorable environmental conditions.

General results from CR:

CR’s Real-World EV Range Tests Show Which Models Beat EPA Estimates - Consumer Reports
Of the 22 EVs we have tested so far, nearly half fell short of their EPA-estimated ranges when driven at highway speeds. We found the biggest difference in range with the Ford F-150 Lightning pickup truck: Its battery ran out after just 270 miles—a 50-mile difference from the EPA estimate. A few luxury sedans also fell short: The Lucid Air missed its advertised 384-mile range by 40 miles. Our Tesla Model S has an EPA range of 405 miles, but we found it was good for only 366 miles of highway driving.