How to Audit Your Dealership Ad Spend (and Agency Report)

The average dealership spent about $739 in advertising per vehicle sold last year — nearly $10 billion industry-wide, three-quarters of it digital. And yet when I sit down with a dealer principal and ask, "which third of this budget would you cut if you had to?", almost nobody can answer. Not because they're not sharp operators — they can tell you their used-car aging and F&I per copy to the dollar — but because the marketing reports they receive are built to be un-auditable.

After thirty years in operations, I've developed a 90-minute audit any GM can run without firing anyone, buying software, or becoming a PPC expert. Here it is, in the order I run it for automotive clients.

Step 0: Confirm you own your own accounts

Before touching a single metric: verify that your dealership has owner/admin access to your Google Ads account, your Meta Business Manager, your GA4 property, and your Google Business Profile. Not "the agency can show you a screen share" — your login, your admin rights.

This matters for two reasons. First, if you part ways with the agency, account history (and the algorithmic learning that comes with it) should stay with the store. Second, agencies that resist giving owners access to owners' accounts are usually hiding either markup or mediocrity. This is the fastest tell in the entire audit.

While you're in there, check one number the agency report never shows: the search terms report in Google Ads. Ten minutes scrolling actual queries tells you how much budget went to searches no car buyer ever typed.

Step 1: Rebuild the only metric that matters — cost per sold unit, by channel

Take last month's invoices and last month's DMS sold log. Build a one-page table:

Channel	Spend	Leads claimed	Sold units traceable	Cost per sold unit

Filling in the fourth column is where it gets uncomfortable. Most stores can trace lead-source on maybe a third of deals, and "walk-in" swallows the rest. That's fixable — the method is called matchback, and I've written a full guide to dealership marketing attribution — but for audit purposes, even the crude version is revealing. If a channel eats 25% of budget and can't be traced to a single deal jacket, the burden of proof now sits with the vendor.

Benchmark anchor: at $739/unit blended industry average, a channel claiming to deliver sold units at $1,500+ each needs an explanation (conquest campaigns and low-volume luxury stores get some grace; "brand awareness" does not).

Step 2: The seven red flags in the agency report

I've read hundreds of these PDFs. The same seven tells show up everywhere:

Impressions as a headline metric. Impressions are inventory, not outcomes. A report that leads with them is leading with its best-looking and least-meaningful number.
No spend shown next to results. If you can't see cost and outcome on the same line, you can't compute anything. That's a choice the report's author made.
Percentages without bases. "CTR up 34%!" — from what, on how many impressions, at what cost? Ratios without absolute numbers are decoration.
Blended branded and non-branded search. Your store name converting on Google is demand harvested, not created. If branded isn't broken out, your "great PPC performance" may be people who already knew you.
"Conversions" that aren't. Click-to-expand a "conversion": is it a sale, a lead, a 10-second page view, a click on a phone number that never connected? Conversion-count inflation is the most common trick in the deck.
Every vendor claiming the same sales. Add up the units every report takes credit for. If the total exceeds what you actually sold — and it nearly always does, often by multiples — nobody is doing real attribution.
No attribution window stated anywhere. A claimed sale needs a defined exposure-to-sale window (30–90 days is the automotive standard). No window means infinitely stretchable credit.

Score one point per red flag. Four or more, and your reporting needs to be rebuilt before your media plan does.

Step 3: Five questions to ask your agency (and the answers that pass)

Send these in an email — written answers are more honest than meeting answers:

"What's our cost per sold unit by channel, and how do you calculate it?" Pass: a methodology involving CRM/DMS matchback and a stated window. Fail: cost per lead, or a story.
"Which campaigns would you cut first if our budget dropped 20% tomorrow?" Pass: an immediate, specific answer. An agency that can't name its own weakest spend isn't analyzing it.
"What percentage of our search spend is on our own brand name?" Pass: a number and a defense of it. Fail: "we optimize holistically."
"Can we get the raw exposure files — device IDs, household matches — for display, geofencing, and CTV?" Pass: yes, with a privacy-safe process. (For what those files should support, see my breakdown of geofencing for car dealerships.)
"What's your markup or margin on media?" Pass: a number. Anything else is a number you wouldn't like.

None of these questions is hostile. Good agencies answer all five easily — and frankly, the good ones are relieved when a client finally asks, because it means budget will flow to what works.

Step 4: Decide like an operator

Audits fail when they end in a feeling. End yours in three lists:

Keep & scale: channels with traceable sold units at acceptable cost.
Fix & verify: channels with plausible mechanics but broken reporting — give them one 60-day window with matchback reporting as a condition.
Cut: channels that failed Steps 1–3 and whose vendor pushed back on transparency.

Run the audit quarterly at this depth, with a deeper annual review or whenever performance shifts sharply. The first one takes 90 minutes. The second one takes 40, because by then your vendors know you read the reports — and the reports get honest fast when somebody reads them.

FAQ

How much should a dealership spend on advertising per car sold?

The 2025 industry average was roughly $739 per new vehicle sold, with about 75% of dealer ad budgets going to digital. Treat that as a blended benchmark — conquest-heavy and luxury stores run higher — and judge each channel on its own traceable cost per sold unit.

How do I know if my dealership's marketing agency is wasting money?

Check for the big tells: no admin access to your own ad accounts, reports led by impressions, branded and non-branded search blended together, undefined "conversions," and an inability to state your cost per sold unit. Vendor sales claims that sum to more than you actually sold confirm nobody is doing real attribution.

How often should I audit dealership ad spend?

Quarterly at the 90-minute depth described here, with a deeper annual review and an immediate audit any time performance shifts sharply or you change agencies. Monthly, just maintain the cost-per-sold-unit table.

What should a good automotive agency report include?

Spend and outcomes on the same line, branded vs. non-branded search broken out, defined conversion types, a stated attribution window (30–90 days for sales), and sold-unit matchback against your CRM/DMS — not just platform metrics.