What Happened??

Leaving work today I had to fill up. I went to a different gas station than what I normally go to. I got 8.7 gallons of regular gas. I then zeroed out all my prior data (ie MPG figues, etc). I took the same route I always take to/from work. 27.5 miles (each way). Traffic was flowing, but slowed in spots. Average speed was 35 mph (pretty typical of my comute speed. I don't believe I did anything significant to up my mpgs, such as going much slower than the flow of traffic. Didn't do that.

To my HUGE surprise, my MPGs, when I pulled into the garage, read a whopping 62.3 mpg. I haven't seen numbers this high since getting the car in late Summer when the weather was much warmer, and they hadn't converted the gas to Winter blend. For pretty much the last few months, i've been averaging (over the identical comute) in the low 50's to high 40's. Granted the weather is a bit warmer than it's been in a while, but not anything close to Spring/Summer temperatures.

I'm absolutley puzzeled about this big jump in mpgs? Happy, but dumbfounded. Has anybody noticed weeks/months of getting one mpg, and then suddenly, a big change in the mpgs under nearly identical conditions? I mean that's more than 20% increase from what I have been averaging the past few months.

 

The differences in mpg's, between what's displayed and what's calculated, are well documented on this site. I know this. On my car, the difference is about 2-3 mpg between the displayed and measured numbers (~ 3%-5% difference), with the measured being lower...but that's NOT what I am talking about. I'm talking about getting in the low 50's (displayed value) for the past 2 months...tonight, I got 62 mpg (displayed). I'm comparing displayed mpgs with displayed mpgs...and for months, it hasn't changed a whole lot.

By the way, you will NOT see high mpgs "for short distances". Quite the contrary, in short distances (few miles), the car is warming up, and therefore, the engine runs quite a bit. The longer my trip, the better my mpg's. My comute is 27 miles. The first few miles i'm in the 30's, but with each mile traveled, my mpgs climb.

 

I've noticed that once I have established and average mpg after a couple of days worth of comute driving (so about 150 miles used for the mpg average)...when I start the car cold in the morning, or when i leave in the evening to go home, that my average mpg will drop between 0.3 to 0.5 mpgs. As the car warms up after a few miles, I slowly get this drop in mpg's back. For example, if my average mpg for two days worth of comuting is reading 50.3, when I start the car cold and begin to drive, the average will drop to some where between 49.7-50.0 no matter how slow I go. Eventually, after 3-5 miles of driving, that average will return to around what it was at the start.

 

Got it, although my trip home did not have any signficant elevation drop, if any.

I traveled almost ~1 mile to the gas station (from my office) before re-setting. Yes, the engine would have been partially warmed up in 1 mile, but not fully. This may have helped me some, but not the 20% increase I experienced tonight. I will have to see if i can come close to these numbers in future trips before I get too excited.