Pleiades 3.6R Posted May 20, 2018 Share Posted May 20, 2018 Yesterday I got back from a road trip with my '18 3.6R and had some interesting (to me anyway) results. It was exactly 2,334.0 miles round-trip. According to my Legacy I averaged 27.4 MPG. What I thought was odd is that the further away from DFW I got the better gas mileage I got. In Colorado I topped out at 31.03 MPG according to the Fuelio app. Then on the way back to DFW my gas mileage got worse and worse the closer I got. What gives? I used the same brand and grade of gas. Link to comment Share on other sites More sharing options...
ammcinnis Posted May 20, 2018 Share Posted May 20, 2018 In Colorado I topped out at 31.03 MPG .... Then on the way back to DFW my gas mileage got worse and worse the closer I got. What gives? 1) Prevailing winds. Aerodynamic drag (~ fuel consumption) varies as the square of vehicle airspeed. Headwinds cost more in fuel than tailwinds save. 2) Air density (~ elevation). Aerodynamic drag is directly proportional to air density. Also, engine pumping losses are lower at higher elevations. For example, the air density at Colorado Springs (elevation ~5000 feet) is ~15% lower than at Dallas (elevation ~500 feet). 3) Tire pressure. Besides the well-known variance with temperature, tire pressure also goes up as the ambient air pressure decreases at higher elevations (~1/2 psi per 1000 feet). Higher tire pressure may mean slightly lower rolling resistance. "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
Imprzme Posted May 20, 2018 Share Posted May 20, 2018 This has me wondering what I'll get next week. Driving from central Canada to Vegas - will be about 3700 miles round trip. Link to comment Share on other sites More sharing options...
Perscitus Posted May 20, 2018 Share Posted May 20, 2018 How about Ethanol content at the same brand stations along the route? Any chance they went from E10 to E0 and then back to E10? Oxygenated fuels in/by big cities also play a factor. How did your Fuel trims #1/3 and #2/4 look, average IAT, Fuel Temps and CVTF temp on each section of the trip? Without a sense of how those and Total Timing as well as the countless compensations affected cruise, your MPGs are without context. Still fairly decent for the EZ36D + TR690 combo. Link to comment Share on other sites More sharing options...
IcEWoLF Posted May 20, 2018 Share Posted May 20, 2018 I have few gas stations here that are 100% ethanol free, worth using it? Link to comment Share on other sites More sharing options...
Perscitus Posted May 20, 2018 Share Posted May 20, 2018 Yup. 100% better for your EZ36D, especially if you use AKI87 or 91. No need for AKI93 unless/until a tune calls for it, zero gains in terms of even knock prevention vs AKI91. Link to comment Share on other sites More sharing options...
ammcinnis Posted May 21, 2018 Share Posted May 21, 2018 ... worth using it? Depends on how you measure "worth." E10 has ~3% lower energy content than 100% gasoline. (Source: U.S. EPA) If the price difference at the pump is more than 3%, "pure" gasoline is not worth the higher price ... at least not in strictly economic terms. "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
Pleiades 3.6R Posted May 21, 2018 Author Share Posted May 21, 2018 I have few gas stations here that are 100% ethanol free, worth using it? Is it Tier One fuel? Link to comment Share on other sites More sharing options...
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