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Unlocking the Full Potential of Google Analytics 4: Maximizing ASC Events with Custom Dimensions

Your GA4 might not be fully set up just yet..

It didn’t seem too long ago that many of us were frantic about getting Google Analytics 4 set up correctly for our websites. While we hope that many of you have weathered the storm, there are still a few housekeeping things to take care of before you can say goodbye to your GA4 setup.

This article is only relevant if you are using ASC events. Some website vendors have set up standardized, out-of-the-box analytics events on your behalf. While this may seem like the work is done, there’s still more to do to maximize the benefits of GA4.

To access more in-depth and rich data points, such as what form types customers submitted or the year/make/models that are being viewed the most, you’ll need to roll up your sleeves and unlock it. This task is known as creating custom dimensions. This is particularly important if you’re working with 3rd party vendors such as chat or service (i.e. Gubagoo, XTime, etc.).

With custom dimensions set up, you can start maximizing your marketing tactics by getting detailed with your events, answering business questions such as “Which VDPs had web forms completed on them?” or “What is my split of New/Used vehicles viewed from my marketing campaigns?”

What is a custom dimension?

Custom dimensions might sound complex, but if you take the “custom” piece out, you’re probably already familiar with them. A dimension is a characteristic of your web traffic, and by default, GA4 tracks many of them, such as “City” or “Source / Medium.” Custom dimensions are functionally the same, except they are customized to you.

ASC events come packed with additional details that allow you to describe them further. For example, asc_form_submission, which measures form submissions, could be further described with a custom dimension called form_type (i.e. book a test drive, ePrice, etc.) To access this data, you must create it inside your GA4 Admin settings.

We’ve identified there are only 19 essential custom dimensions ASC is compatible with 59 custom dimensions. However, Google’s limit is 50 per property. At Autograph, we’ve curated just under 20 custom dimensions that you need to cover most of your business questions.

You’ll find these 19 later in this guide. And with those created, it will help you elevate your data analysis and ensure you’re collecting and using data to drive results. If you’d like to use or learn more about the others you can use, access the full ASC custom dimensions guide here and Google’s custom dimensions limits here.

How do I add custom dimensions?

Adding custom dimensions to your account is easy. Choose a GA4 property of your choice and open your admin settings (gear icon on the bottom left):

Under ‘Data Display’ click on Custom Definitions:

Click on ‘Create custom dimension’ button

From here, you will need to copy and paste the custom dimensions from our list into the Dimension Name and Event Parameter fields. For this example, we’re creating ‘affiliation_id’, which refers to the ID of an agent, company or session connected to an event. If you wish, you can copy our descriptions and paste them into the ‘Description’ field.

Once you are done, hit the Blue save button.

Adding the custom dimensions should only take a few minutes to do for each of your properties.

List of Custom Dimensions

Here is the complete list of our essential custom dimensions for ASC. These 19 represent a list of commonly used and shared dimensions within the ASC model. Please note that you must use this precisely as listed to avoid any issues related to case sensitivity with GA4.

  • affiliation_id
  • comm_type
  • department
  • event_owner
  • event_action
  • item_category
  • item_color
  • item_condition
  • item_fuel_type
  • item_id
  • item_inventory_date
  • item_make
  • item_model
  • item_number
  • item_price
  • item_type
  • item_variant
  • item_year
  • page_type
  • store_name

What do these all mean?

One of the challenges with custom dimensions is that they’re sometimes not self-explanatory about what they do or represent. However, as you familiarize yourself with them, you can build reports without referencing this guide or the ASC handbook.

affiliation_id and event_owner:

ID number of agent, employee, company name, phone extension, or session connected with the event.

Why this is important:

  • Easily identify traffic by 3rd party vendors and assess which tools are most effective.


Type of communication that took place.

Why this is important:

  • Learn how customers utilize your chat and service apps, whether they prefer chat, texts, or calls, and whether they are utilizing your chat bots more for service or sales.
  • Assess the strengths and weaknesses of each tool.


Department associated with the event

Why this is important:

  • Pinpoint which departments receive the most engagement from your 3rd party chat tools.

‘item’ custom dimensions:

Includes specific vehicle information within your data

Why this is important:

  • Get insights on which year make and models are receiving traffic by easily searching data in GA4 using these values. Without these custom dimensions, this is not possible.
  • VIN and Stock Numbers is data that can be included in the item_id custom dimension. Having this in GA4 makes it possible for offline sales attribution when comparing your CRM data.
  • Utilize the item_condition custom dimension to show which VDPs (new or used) are receiving the most leads / VDP views.


Type of page event took place.

Why this is important:

  • Easily segment your traffic in GA4 by ‘service’ pages etc.


Legal name of website customer

Why this is important:

  • Having this data will be key when doing aggregate reporting, as you will easily be able to segment your data using store names.

Essential Data Quality

Using custom dimensions in GA4 is akin to personalizing your car dashboard with more gauges that matter. Imagine you’re used to checking your car’s speed and fuel level, but now you also want to monitor tire pressure and outdoor temperature to make more informed decisions on the road.

Custom dimensions can ensure your advertising budget is used efficiently to attract serious buyers to your site, boosting the chances of making sales.

The value of your analysis hinges on data integrity. Notice discrepancies in your ASC data, such as errors in ‘store_name’ or missing ‘item_make’ and ‘item_model’ from VDP-originated leads? It’s critical to address these with your vendor for accurate tracking.

At Autograph Analytics, we regularly provide ASC QA and vendor follow-up for all of our clients, and we would be happy to share some more insights to ensure you are getting the cleanest data possible for ASC.

Reach out to us at for more information.

Stay tuned for our upcoming article, where we’ll dive into practical applications of custom dimensions in reporting to enhance your ASC data utilization for better marketing outcomes.


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