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.
I only have 2 tanks worth of experience but have found the FE reported by the car & ScanGauge to be overstated (20%) compared to the hand calculation. It's so bad it makes the Gen 2 MFD look like a precision instrument. I wouldn't bank on that 62.3. The car's hot so for a short distance (maybe a few miles) you can see fantastic numbers. Enjoy it while it lasts.
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.
The best way to get impressive mpg is to wait until the car is fully warmed up, then get gas and reset the Consumption meter (or whatever is equivalent in the 2010). However, the next cold start and warmup cycle will kill the average.
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.
I use one trip gauge for the tank, the other for shorter periods, typically each day. The daily gauge varies drastically -- starts in the single digits, gets up to a good number at work, then in the evening drops ~5 units before climbing back up to a decent figure. As dogfriend points out, warming the car before resetting the meter can produce some very impressive numbers for the remainder of the trip. If the trip has a net elevation drop, those numbers can be absolutely incredible. But enjoy it before returning, as the cold engine and the uphill climb will kill the number.
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.
Something similar happened to me last week. Our previous 2 tanks yielded mpg in the low to mid 40s (computed), with mid to upper 40s on the Trip A display. Last week I got almost 9 gallons of gas and since then the reset trip display is in the mid 50s! Average temperatures did go up some, maybe from low 20s to low 30s, but I don't think the temperature difference is large enough to account for the mpg change. I haven't seen consistent consumption numbers in the 50s since early fall. Could the improved mpg be due to the gas?
If your mpg dropped you never truly get it back. I think the point Dogfriend was trying to make is that every time you have a cold start then you have a negative to your overall MPG number. If you keep the same routine then you will set a consistent average. When you reset everything while the car is warmed up and in closed loop then you now have a positive to your MPG number. If you kept driving with your normal cold start routine the average MPG will drop down but you should still be higher than normal because of that hot car reset unless you make other alterations to your normal driving routine on that tank. Does that make sense? The point is, if you reset while the car is hot then of course whatever trip you make on that day is going to look better than if you had reset while cold.
