How much laundry soap do you really need?

I have probably devoted one nanosecond of my extraordinary life to thinking about laundry detergent, but it seems I keep posting about it because I find it interesting. Not in a laundry kind of way, but because it says something about our being creatures of habit.

Okay, so here we go again.

Alina Tugend asks a lot of questions in a piece in The New York Times like "How much soap should I put in my washing machine?" If you're like me you look at the soap bottle with its incredibly complicated cap and you just pour some in it and dump it in the wash.

Well. Let's listen to Ms. Tugend.

The No. 1 sin, according to repair people and appliance experts, seems to be adding too much soap to washing machines or dishwashers.

“Nobody thinks they use too much soap,” said Vernon Schmidt, who has been a repairman for almost 35 years and is the author of a self-published book, Appliance Handbook for Women: Simple Enough Even a Man Can Understand. But apparently most of us are in denial.

Washing machines and dishwashers are made to use far less water now than older models and, therefore, need less soap. And detergents have also become increasingly concentrated. So a little goes a long way.

“Most people use 10 to 15 times the amount of soap they need, and they’re pouring money down the drain,” Mr. Schmidt said.

So he thinks I'm going to measure one-fifteenth of however much it is I pour in the cap. Okay. You can read the instructions but the soap maker is probably recommending too much. I'm reminded of something my friend Ben Cheever once wrote: with the simple instructions on shampoo, "Rinse. Repeat." the shampoo maker doubled consumption. Hmmm.

Here's a little test Mr. Schmidt recommends.

Take four to six clean bath towels, put them in your front-loading washing machine (one towel for a top loader). Don’t add any detergent or fabric softener. Switch to the hot water setting and medium wash and run it for about five minutes.

Check for soap suds. If you don’t see any suds right away, turn off the machine and see if there is any soapy residue. If you see suds or residue, it is soap coming out of your clothes from the last wash.

“I’ve had customers that had to run their towels through as many as eight times to get the soap out,” Mr. Schmidt said, who lives in Indiana. He offers other handy advice on his Web site, refrigdoc.com.

It's a game. Everything's a game.