Tesla factory. Image source: The Motley Fool.

Just as electric-car maker Tesla Motors (TSLA 0.38%) is wrapping up its third quarter, CEO Elon Musk has sent a companywide email congratulating employees on what looks set to be its best quarter "ever in Tesla history." But this achievement required a concerted effort to rally the troops in a big quarter-end push.

Here's what investors should know.

Unsustainable tactics?

While Musk's Sept. 28 email acknowledged that Tesla's third quarter looked poised to be the company's "best ever," there were some tactics at play to get these results that simply may not be sustainable.

For instance, the main subject of Musk's Sept. 28 email was actually a reminder to employees not to discount new Tesla vehicles to make a sale:

[I]t is absolutely vital that we adhere to the no negotiation and no discount policy that has been true since we first started taking orders ten years ago. This is fundamental to our integrity and we maintained this policy even through the terrible depths of the great recession of 2008/2009.

It is fine to have a discount on cars that have been floor models, were used in test drives or were damaged before delivery. All we are doing there is assigning an accurate price to the vehicle. However, there can never -- and I mean never -- be a discount on a new car coming out of the factory in pristine condition, where there is no underlying rationale. This is why I always pay full price when I buy a car and the same applies to my family, friends, and celebrities, no matter how famous or influential.

Musk's corrective email followed Pacific Crest Securities analyst Brad Erickson's note to investors (via Bloomberg) stating that the firm had detected "aggressive Model S discounting at U.S. sales centers intended to maximize Q3 deliveries."

Image source: The Motley Fool.

In addition, Musk himself urged employees in a companywide Aug. 29 email to cut any unessential costs during the quarter -- a move that is obviously not sustainable over the long haul:

We are on the razor's edge of achieving a good Q3, but it requires building and delivering every car we possibly can, while simultaneously trimming any cost that isn't critical, at least for the next 4.5 weeks. Right now, we are tracking to be a few percentage points negative on cash flow and GAAP profitability, but this is a small number, so I'm confident that we can rally hard and push the results into positive territory. It would be awesome to throw a pie in the face of all the naysayers on Wall Street who keep insisting that Tesla will always be a money-loser!

Tesla's resolute focus on achieving profitability in Q3 has clearly pushed the company to make some near-term sacrifices, some of which Musk isn't evening condoning.

Why Q3 is important

As Musk explained in his Aug. 29 email, the company's third quarter is particularly important because it represents the company's last quarter before it starts aggressively spending cash on bringing its Model 3 to market, an effort that will make it nearly impossible for Tesla to report positive cash flow, at least until the Model 3 is in full production. Further, Tesla believes reporting positive cash flow and profitability in Q3 will put the company in a better position "to convince potential investors to bet on us" when Tesla raises capital in Q4 to complete Model 3 factory preparations and its Gigafactory.

In light of Tesla's tenacious, yet arguably unsustainable, efforts to potentially get to positive cash flow and profits in Q3, should investors discount the quarter's results? Not necessarily. In Tesla's trailing-12-month period, the company reported negative operating cash flow of $332 million and negative free cash flow of more than $1.6 billion; so it's still impressive Tesla can even come close to positive cash flow amid rapid growth in such a capital-intensive industry. But investors should at least view the results in the context of the rigorous quarter-end push it took to achieve them.