I have recently purchased a new 2004 Tacoma (V6, 3.4l). The owner’s manual states the following: All Toyota vehicles come from the factory with natural petroleum-based engine oil. Toyota is currently recommending API grade SJ or SL, or ILSAC multigrade petroleum-based engine oil for our current model year vehicles. In moderate climates, this oil should have a Society of Automotive Engineers (SAE) viscosity rating of 5W-30. In our high mileage tests with preventative maintenance performed at the recommended intervals, the recommended natural petroleum-based oil has provided excellent service. If you decide to use synthetic oil for the engine, it is best not to switch until the first scheduled oil change. Synthetic oil should meet or exceed the specifications provided in your Owner's Manual. Even if synthetic oil is used, we do not recommend a longer oil change interval. Also, once synthetic oil is used, you should keep using it and not switch back and forth with natural petroleum-based oil. The “first scheduled oil change” is at 5,000 miles and based on my driving habits of short trips, 5,000 miles will be 6 months! I was wanting to switch to Mobil 1 or Amsoil as soon a possible plus I was wanting to do a 500, 1000 and 3000 mile oil change. And every 3,000 miles thereafter since that would be about every 4 months. What would you recommend? Which oil? Mobil 1 or Amsoil? Which Amsoil? What the difference between the “regular” synthetic which has a “100% Synthetic” label on the bottle and the XL-7500 that just states “Synthetic” ? At a $0.35 retail price difference the price is NOT a factor. What should I do????