Yesterday's news that Volkswagen and the U.S. EPA had reached agreement on a deal to address VW's diesel-emission cheating scandal brought as much confusion as clarity.

The carmaker and the regulator said they had agreed on the general outline of a deal to offer owners a choice of either modifications or buybacks.

There was also a separate offer to compensate owners up to $5,000 apiece.

DON'T MISS: VW settlement with EPA announced over diesel emission scandal

Other terms covered future efforts VW would make to make up for the excess emissions its cars produced, and various other remediation and corrective measures.

But comments and questions on our report yesterday indicated a wide degree of confusion among owners and observers alike.

So we've broken it down into five questions to clarify the most common areas of misunderstanding.

Consumer Reports tests 2015 Volkswagen Jetta TDI diesel in 'cheat mode,' October 2015 [video frame]

Consumer Reports tests 2015 Volkswagen Jetta TDI diesel in 'cheat mode,' October 2015 [video frame]

(1) Which diesel vehicles does this agreement cover?

It applies only to Volkswagen and Audi sedans, hatchbacks, and wagons sold with 2.0-liter four-cylinder TDI diesel engines from the 2009 through 2015 model years. 

Those are:

2015 Volkswagen Golf TDI, Golf SportWagen TDI, Jetta TDI, Passat TDI, Beetle TDI; and 2015 Audi A3 TDI

These 67,000 vehicles are all fitted with the "EA288" 2.0-liter four-cylinder diesel engine, which replaced the older engines used in 2009-2014 TDI models. These are all fitted with a Selective Catalytic Reduction emission aftertreatment system that requires the regular addition of liquid urea solution.

2012 Volkswagen Passat TDI Six-Month Road Test

2012 Volkswagen Passat TDI Six-Month Road Test

2012-2014 Volkswagen Passat TDI

These 90,000 diesel Passats built in the U.S. use an older "EA189" engine, but also include a Selective Catalytic Reduction system too.

2009-2014 VW Jetta TDI, Jetta SportWagen TDI; 2010-2014 VW Golf TDI; 2012-2014 VW Beetle TDI; and 2009-2013 Audi A3 TDI

These 325,000 cars, fitted with the old "EA189" 2.0-liter four-cylinder diesel, were always expected to be the most challenging to update, because they are not fitted with the urea system. They also include the oldest vehicles in the group, some sold as early as late 2008, and may include the largest number of vehicles with high mileages already driven.

ALSO SEE: VW diesel scandal now 6 months old; what have we learned?

NOTE: Yesterday's announcement does not apply to various Audi, Volkswagen, and Porsche sedans and SUVs sold with the 3.0-liter V-6 TDI engine.

Those vehicles are the subject of separate negotiations.

They include the TDI versions of the Audi A6, A7, and A8 luxury sedans and Q5 and Q7 crossover SUVs, as well as two more SUVs: the Volkswagen Touareg TDI and the Porsche Cayenne Diesel.

2014 Audi Q5 TDI, Catskill Mountains, Oct 2013

2014 Audi Q5 TDI, Catskill Mountains, Oct 2013

(2) How much will Volkswagen pay me for my used diesel car if I go for the buyback?

Buyback prices were not released yesterday, and a fair way to value the used diesel cars for repurchase is likely still being negotiated.

The values of used VW and Audi diesel cars have plummeted since mid-September, when VW's emission cheating first became public.

Most analysts expect the buyback program to employ used-car values established by a neutral third party, perhaps Edmunds or KBB.

2012 Volkswagen Passat TDI Six-Month Road Test

2012 Volkswagen Passat TDI Six-Month Road Test

Those values will vary by model year, features, and miles covered, but would almost surely be the ones published as of August 2015, just before the scandal broke.

The company may offer a premium on top of those values, as other companies have done in earlier buyback programs, to encourage more owners to give up their vehicles.

(3) But I thought VW was only paying $5,000 for the buyback?

No, the buyback prices have yet to be established (see above).

Note that the figure of $5,000 is only a rumor; it wasn't confirmed yesterday in the information that was released about the "agreement in principle" between VW and the EPA.

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We do know that VW has agreed to set up two compensation funds.

One would pay an unspecified amount—described only as "substantial compensation"—to owners who agree to forgo the legal right to sue Volkswagen.

The Federal district-court judge who imposed the deadline, remember, is overseeing a consolidated set of class-action suits by owners who are suing VW for deceptively selling them cars that it knew did not meet emission standards and violated the law.

2015 Volkswagen Golf TDI SE

2015 Volkswagen Golf TDI SE

The agreement for that "substantial compensation" to be offered to owners may be a way to reduce the number of owners suing the company by offering an alternative settlement that's quicker and more certain than the outcome of a lengthy trial.

So whether it's $5,000 or some other number, that payment is entirely separate from the price VW would have to pay to buy back a diesel car.

(4) What effect will modifications have on my car if I want to keep it?

The answer here is: We don't know.

First, it remains unclear whether VW will offer modifications to all 482,000 four-cylinder TDI cars, or only some.

2015 Audi A3 TDI, New York City, Nov 2014

2015 Audi A3 TDI, New York City, Nov 2014

We won't learn that until June 21, when the full terms will be released.

Analysts have said modifications to the 325,000 cars without urea-injection systems would be hugely costly, requiring lengthy re-engineering and testing procedures.

It's entirely possible they could cost more than the cars are worth.

Second, updates will likely affect performance, fuel economy, or both—which were precisely the reason many buyers chose the VW or Audi diesel models to begin with.

READ THIS: European fix for VW diesels complies with law, but real-world emissions still too high

VW's first plan for updates was rejected by regulators earlier this year because it lacked information about their impacts on fuel efficiency and performance.

But full details of the potential modifications won't arrive for two more months.

The fact that VW has ended up offering to buy back even those cars whose modifications were thought to be limited to software updates suggests that those impacts may be non-trivial.

2013 Volkswagen Beetle TDI

2013 Volkswagen Beetle TDI

(5) When will we get more details?

As part of yesterday's announcement, Judge Charles Breyer also established two new deadlines for all parties to meet.

Volkswagen and the EPA must submit all final details of the agreed-upon settlement as an official court filing on or before June 21.

Then the court will hold a preliminary hearing on the deal on July 26, after the public has had a chance to review the filings—with owners and their lawyers likely first in line.

Until then, according to VW Group of America spokesperson Jeannine Ginivan, the agreement in principle will remain confidential among all the parties.


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