This is what I have done:
- mobil 1 0w-30 oil
A well maintained vehicle is more efficient so if you don't really keep up with the maintenance here are a few places to start. If your spark plugs have been in for over 30k miles its time for new ones. This is also a good time to change the airfilter and inspect the charcoal filter. Change all oils to synthetics and keep them clean and fresh. Correct tire pressure. Have a front end alignment done. Ditch all nonessential items from inside vehicle. A lighter vehicle is more mpg friendly. Don't run aggressive tires if you don't have too. Same goes with wide tires and/or wheels. The list could go on and on. For what its worth I consistantly get 19-20 mpg city and 22-23 on the freeway with my 08 SR5 4x4 V6.
Heh... I don't REALLY understand how oil works, in terms of the numbering and weight. I know it has to do with the temperature and how it flows, but I've heard that going lighter can be bad for your engine, and actually cause mpg's to go down. I was just curious as to what you've heard, and how that oil is working?