Is the grass alive now? Since it went dormant in the summer it was probably Kentucky bluegrass. And if it was, then watering it should bring it back without overseeding.

The depth of the soil has little to do with the performance. He had to dig around to find the thin spots. Apparently the thin spots didn't jump out and shout, "NOT ENOUGH SOIL!"

He should come to this forum (or some others I'm not allowed to name), and do some reading about lawn care. Watering once a week in the heat of summer is MANDATORY. If he is unwilling to do that then he will be facing this issue every year.

Adding topsoil (or loam) to the yard will do nothing, NOTHING, to help. If he is lucky the added soil will not redirect rainfall drainage into his basement. But that is a very serious consideration and excellent reason all by itself to not add more soil to a lawn that is draining fine.

Core aerating is unnecessary. If the soil is hard, apply any clear shampoo at a rate of 3 ounces (minimum) per 1,000 square feet once and follow up with 1 full inch of water. Measure an inch of water with cat food or tuna cans. In a week water again a full inch without the soap. Then on the second week, repeat the shampoo and full inch. That should be all he needs to have really soft soil for the next several years. I like shampoo because it is dirt cheap. There are exotic surfactants you can get to do the same thing, but those cost about $70 for a gallon. And a gallon of that concentrated stuff will last the entire neighborhood for 100 years.

Start watering and see if the grass comes back. If he does not see 80% of it coming back, then yes, overseed with a full sun type seed. Full sun will be a blend of Kentucky bluegrass and turf type tall fescue.

NOW is the time to seed. Don't wait until spring. But again, I would not seed if the grass comes back.

Watering is not a big deal if you do it right. Once a lawn is mature, as his already is, then it should get a full inch of water once a month in the cool months (not yet) and transition to once a week in the hottest heat of summer. Many people try to water 1/7-inch every day to get the full inch per week. That is the worst thing to do. Why? Because the grass roots "learn" that they only need to be 1/4 inch long. The soil below 1/4 inch deep is too dry to support root life. Whereas deep watering encourages the roots to grow up to 3 feet deep for some grasses. That grass can stand to go several weeks without watering. Another reason for deep infrequent watering is to discourage weeds. Weed seeds need continual (daily) watering to germinate. If you only give them monthly water, they will dry out and not germinate. Of course Mother Nature always throws a wrench in the works, but at least you should not be helping the weeds along.

What kind of fertilizer did the lawn service apply? Was it liquid? If so then he should be able to use a starter. The problem with chemical fertilizers is they tend to interact with each other. That is one reason I've gone to full organic fertilizers. They don't interact with anything except soil microbes. They don't do anything directly to the plants. If he wants to apply an organic fertilizer, he can do that any day of the year including the day he seeds...if he decides to do the seed deed.

So most important is to learn how to water.
Second is to not add more topsoil.
Third is to spray shampoo instead of aerating. Probably his lawn company is urging him to aerate because they have a big boat payment coming up in October. Shampoo costs $0.30. Only clear shampoo.

Thanks dchall, I will pass along the post and try to re-introduce him to the forum.

Thanks again

Excuse me, but core aerating IS necessary, and shampooing a lawn to reduce soil compaction is not much better than snake oil. But don't just believe everything you read online -- believe the agents at MSU Extension.

If you don't have water retention repellency problems in your soil, spraying it with shampoo is completely unnecessary.

Here is a link that might be useful: Pros and Cons of Those Lawn Fertilization Tips

MulchMama is one of the skeptics who is deathly afraid to spend his/her own $0.50 to try shampoo but will defend the Ivory Tower soil researchers who have also not tried it but don't have any problem writing a snide review of it. Part of the beauty of these Internet forums is we can listen to what other people are trying and, if it is easy enough, we can try it ourselves. And the forums are read by thousands of people and contributed to by hundreds of people. And some people will see the shampoo thing and scoff. Others will try it. Of those who have tried it, nobody has written in to say it didn't work. But many have written in to say how it really works! I was a huge skeptic at first. I wasn't sure if I should trust the guy who was promoting it. I had already developed an excellent way to soften hard soil, so I was reluctant. But for the cost of a little shampoo I would look really stupid if I went back and tried to claim it didn't work. So I tried it. It worked. It worked so well that I have not mentioned my method as practical method since then. That was in 2011. After only one application my soil still gets soft when it rains or I water it.

The reason it works I believe goes beyond what the MSU people are thinking. They are talking only about hydrophobic soils. Golf courses develop a hydrophobicity from brief daily watering. A hydrophobic fungus grows at the surface and actually repels water. By spraying their expensive surfactants, the water flows right through. This was the Genesis of the shampoo idea. I believe the shampoo works on regular soil to soften it by promoting the growth of beneficial fungi necessary for moisture penetration. The shampoo allows moisture much deeper into the soil where it is retained by cooler temps (less evaporation) and moderates the temperature. Under these ideal conditions the beneficial microbes repopulate and bind with the soil to allow better moisture penetration. Please read the first four paragraphs at this USDA link.

In addition to being costly and almost dangerous for a homeowner to do, core aeration brings up weed seeds which have been buried in the soil for years. It brings them right to the surface where there is no shade to keep them from germinating. And if you follow up your core aeration with a LOT of water (like you should), then you are going to germinate those weed seeds immediately.

Core aeration can be very beneficial for a multitude of reasons in many circumstances.
Shampoo may or may not be benefical, for a dollar and a half hour of time, there usually isn't much to lose especially when the soil exhibits hydrophobic qualities. However, applying shampoo (sufactant) to sandy soil can be very detrimental to the turf. Use caution.