I have a 15 mile Suburban Commute. Half at 25-45 mph with 8 traffic lights and 3 Stop Signs. The other half is open highway at 55-70 mph. Traffic is light. The 15 miles generally takes about 25 minutes.
In your opinion how should I set the City vs Highway % which I currently have at 50%?
Distance or time are the best methods, but the most important thing is to be consistent. I tend to use a hybrid of distance and time with the greater weight being given to time. This is because I use engine hours to set my post warranty service schedules. The benchmark 3,000 mile oil change interval was actually based upon 100 engine hours at an average of 30 miles per hour. That is the reason that back about 15 years ago some manufacturers started with the 5,000 mile interval for vehicles with heavy freeway miles, it was the same 100 engine hours but based on a 50 MPH average. The 7,500 mile interval came about with some of the newer generation oils and synthetics that manufacturers feel can stretch the inverval to 150 hours without danger to the engine.
I would say the slower portion takes about 16-18 minutes (7.5 miles) depending on lights and the faster portion (7.5 miles) approximately 7-8 minutes.
I was concerned maybe my slower portion was not congested enough to be considered true city as my average seems to be about 2 mpg better than anyone with a similar vehicle. This could be affected by the fact I only use G100 (No Ethanol) Gas.
I'm pretty sure that the non-ethanol fuel is at least partly responsible for your better gas mileage. Here in California ethanol mixed gas is all that we have and I average about 2-3 miles less per gallon than people with the same model car in states that don't mix ethanol. California is supposed to be an environment friendly state, but they make us use fuel that is 10% (or more) less efficient than other states.
Yes, ethanol blended fuel definately decreases mileage and the average speed of your non highway commute is probably higher than some, both will add up to economy increases. Be proud of your better than most MPG figures, I certainly am proud of mine. Also be aware that many of us that are active here on Fuelly are extravigilant at squeezing the most mileage out of our tanks and fuel, that is after all the purpose of the site. To track and share our experiences with other drivers who want to maximize their fuel economy so it only makes sense that you're doing better than the average. Well done, keep up the good work.