Never listen to dealers and auto shops about oil change frequency. The more often you change your oil, the more money they make. Their propaganda campaign about changing oil every 3000 miles is just that, propaganda.
"Consumer Reports, with one of the most widely respected product testing laboratories in the world has just released the results of an extensive test on oil brands and oil changes, as well as other issues regarding car care. In the process, the test demolished much of the conventional wisdom regarding car lubrication. The two most surprising results: the frequency with which oil is changed doesn't matter after the first few oil changes on a new engine, and the type or brand of oil used can not be shown to make any difference.
The testers placed freshly rebuilt engines in 75 New York taxis and then ran them for nearly two years, with each cab racking up 60,000 miles, placing different brands and weights in different cars and changing the oil at 3,000 miles in half the cars and 6,000 in the other half. At the conclusion of the test period, the engines were torn down, measured and inspected. The conclusions: Regardless of brand of oil or weight, no measurable differences could be observed in engine wear. Furthermore, there was no difference among cars which had oil changed at the shorter or longer interval.
Does this have any bearing on the enthusiast's car, which is given almost the opposite usage stored for long periods of time then started and driven for short distances? The tests suggested that our type of usage would build up sludge and varnish, indicating that an annual or semi-annual oil change is a good idea regardless of how much mileage the car is driven. But there is little indication that the brand or weight needs to be given serious consideration, and synthetic oil has no discernible advantage over the old stand-bys. More information on the tests and results can be obtained from Consumers Union or Consumer Reports available at most libraries."
