OK, for me this worked for better mileage

[coolvanillagt]

OK, I'm missing it...Royal Purple?
And I just completed a roundtrip to Cali, cruise set at 83-85, occasional passing burst up to 95-100 and the a/c on all the time. Best was 24mpg. And I didn't get the Mobil One yet, just the dealers regular stuff. But Royal Purple?....

[MichaelDay]

http://www.royalpurple.com/techrp/summary.html for more information on Royal Purple. It has been around for many years. Mobil One is still one of the most commonly used premium oils.

[strangelove]

Well two things probably happened to give you better gas mileage. First Mobile 15,000 has higher amounts of detergents in it's formulation which gives it better viscosity. Those same detergents will help clean away some of the slug older cars develop, slightly increasing engine performance.

Second, most refineries are switching from their summer blend gasoline (California), to their normal gasoline. You should see a slight increase in milage because of the switch.

[marlow_cruiser]

Originally Posted by ElectricBlueGT

My past two trips have averaged 30-31 MPG. I have an '03 GT with an AutoStick, Stage 1 and a plastic intake manifold. My two trips (each 360 miles minimum) were done at 70 MPH with cruise control. 360 and 378 miles, each on 12 gallons of gas.

Scott

Hey Scott,
I just recently purchased an 03' GT Turbo with autostick. Using 5-30 Valvoline syn, I have been getting about 21 average, and 25 straight highway. Could you please give me more detail on how you're getting 30-31 mpg? What octane fuel? K&N filter? etc. Whatever you can add will help.

Thanks,
Ray