A tube-head goes to buy a new car. He goes to the dealership and asks for a 30 day test-drive. He then takes that car to all the places he normally goes, at all times of day, making sure to bring along all the people he would normally carry. He takes obsessive notes while doing this. He drives the same road about 50 times during the 30 day trial. This process is repeated for about 10 different cars.
When he finally buys the car and takes it home, the first thing he does is change the oil. Not happy with the result, he will buy a different brand of oil and change it again. Of course, the same roads are tried after each oil change, again making obsessive notes. His friends are divided in two groups; those that cannot get enough of the oil stories, recommending ever more expensive and hard to get brands of oil, and those that are now starting to avoid him. After about 6 months, he settles on a motor oil that is very hard to get and costs about 1/3rd of the price of the car, but it sure makes it run much better.
And every saturday morning, his spouse just wants to get the groceries. She gets in the car, so does he. He starts, frives out of the driveway, and proudly asks as they get to the grocery store: "Well, what do you think?" meaning of course the improved smoothness with the new oil and all, to which she responds "It sure is busy this saturday morning."
To make up for this, he takes his friends out on saturday afternoon, to drive down the same piece of road he has driven down 50 times before...