A Google Ads manager on r/PPC posted a before and after from a single campaign. The client is a reseller of computer aided manufacturing software for CNC machining, and the campaign targets the name of the software they sell. He says he turned AI Max on for one week, switched it off, changed nothing else, and pulled the search term report for both weeks.
The strategy
The test is deliberately small. One campaign, one variable, two weeks of search terms side by side.
According to the post, the week with AI Max on produced 955 distinct search queries, and 72 percent of reported spend went to things that had nothing to do with the product. He lists what it bought: two European woodworking machinery manufacturers by company name, "free cam software for cnc", "cnc software free download full version", "autocad software". The week after switching it off produced 30 distinct queries, every one containing the software name, and nothing worth blocking.
He raises the caveats himself, which is what makes the test worth copying. Target CPA was running the whole time and the campaign already carried a couple of hundred negative keywords, so this was not a bare account left open. Google reports search terms for only about half of actual spend, so his percentages are of the reported half. He also dumped more negatives on partway through the second week, though he says the last two days looked like the first five.
His conclusion is that negatives cannot fix this on their own, because you cannot write a negative for a German machinery company's name before you have seen it appear.
Why it works
Search term counts are one of the few numbers in Google Ads that cannot be smoothed by a bidding strategy. Conversions lag, CPA moves for a dozen reasons, but the list of queries you paid for is a direct readout of what the matching layer decided you meant. Counting distinct queries in a fixed window, on one campaign, with everything else frozen, gives you a comparison your account manager cannot argue with.
How to test AI Max before you leave it on
Pick one campaign with a narrow, unambiguous product term. Run AI Max for seven days, then turn it off for seven days, and change nothing else in either week. Download the search term report for both windows and count distinct queries and the share of spend on terms that do not name your product. If the on week is mostly discovery you would never have bid for, you have a number to point at rather than an opinion.
Credit: u/Wilson-KingOfPrussia on Reddit