In order to help boost sales at a time when the entire industry has been experiencing a major slowdown, Audi has recently been advertising a 0 percent APR financing deal for up to 72 months on a select group of 2019 cars and SUVs. Buyers can even defer payments for up to 60 days. However, Cars Direct did some national inventory checking and realized something significant: just about every Audi model eligible for this offer is sold out.

Take the 2019 Audi A5, for example. That zero percent interest for six years offer is probably the best deal ever seen for the model, but there are only just over 500 examples left in stock nationwide.

The 2019 Audi Q5, one of the brand's best-sellers, faces a similar situation with only around 600 of them still available. So what can customers do if they can't find the 2019 Audi they want because of a lack of inventory? Simple, opt for a 2020 model instead.

That might sound like the best solution and it could be for some, but there's a catch: most 2020 Audis don't have the 0 percent APR offer. Instead, the current deal is for 1.99 percent for 66 months. For a $50,000 vehicle, that amounts to a bit over $2,800 in interest for the loan period. With this new information coming to light, Audi may want to make some adjustments to its latest deals.

There's also another key reason why it should reexamine things: BMW. Audi's German rival now has a 0.9 percent offer for 60 months in addition to having "APR Credits" valued between $2,500 and $7,500.

The good news is that automakers can quickly adapt their sales strategy based on what the competition is doing and national inventory. Given the above information, it'd probably be a wise idea for Audi to do this.