I've used Mobil One in my 95 Maxima since about 15,000 miles, changing every 3000. Now have 82,000 on it and it runs smooth as silk, no tune ups except I changed plugs at 60,000 mi. The price difference with regular oil really isn't much of a factor if you think about how it compares with the other operating costs of a car. Changing it yourself also saves money.
I think waiting 25,000 miles for changes is way too long, and no car manufacturer would recommend that. And dirt builds up no matter how good the oil is.