eBay Motors includes an eBay store with its Local Market subscriptions for car dealers. Some of the capabilities featured with a store includes customization, SEO, & traffic reports. These are very useful features that should be utilized in most any case by car dealers.
I say hands down that YES a dealer should promote the heck out of his eBay store, especially if he has more than cars listed for sale, e.g., parts, accessories, etc. Despite not having any data, information to justify this, there are logical reasons why I think you should.

For starters, your eBay store is a brand commensurate transaction site. In most cases, not even your dealership website offers this capability to customers. You want to draw attention to this fact and you also want to avoid sending visitors on your site elsewhere, even if to your own eBay store because they can access your competitors.

Second, by promoting it (via any form of advertising online or offline) you are giving your brand more arms and additional reach. This is not to suggest that a dealer should have a myriad of web spaces they promote, but something like an eBay store which has a unique value proposition that can't be matched elsewhere, yes you should create awareness to that.

Third, eBay is a niche market. Some people live by eBay, including some auto shoppers. You can exceptionally target these customers and become the premiere player in this space b\c many do not promote their eBay store.

Now also, from an SEO perspective, by promoting your eBay store in Organic Search you can push your competition off highly coveted Search Engine Real Estate. Think about this from a customer point of view. He or she performs a search on Yahoo! and discovers not just your website in the search result (SERP), but also discovers your eBay store. This is good for nixing your competition, saturation search markets, and creating more brand awareness of your dealership.

So yes I do think that a dealer's eBay store should be promoted, especially if you have more than just vehicles for sale on it.

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Ryan Gerardi