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When you select the screen that shows what you're currently getting for MPG, how accurate is it? Is it less accurate right after you fill up, and it starts back to zero?

Last Saturday, I filled up and immediately went on the highway to a shooting range ~22 miles away. I kept checking the number and it kept going up and ended up topping out at 45.3 mpg. I was impressed. However, today I went back out,....same route,.....with a tank on 3/4th still in the tank, after a week of basic town driving. The average mpg was at 31.1 mpg when I started my trip out to the range. Today, it only made it to about 32.5 mpg. Same route, using cruise. I was using A/C today, but surely that wouldn't have brought the numbers down that much.

Thoughts?
 

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When you select the screen that shows what you're currently getting for MPG, how accurate is it? Is it less accurate right after you fill up, and it starts back to zero?

Last Saturday, I filled up and immediately went on the highway to a shooting range ~22 miles away. I kept checking the number and it kept going up and ended up topping out at 45.3 mpg. I was impressed. However, today I went back out,....same route,.....with a tank on 3/4th still in the tank, after a week of basic town driving. The average mpg was at 31.1 mpg when I started my trip out to the range. Today, it only made it to about 32.5 mpg. Same route, using cruise. I was using A/C today, but surely that wouldn't have brought the numbers down that much.

Thoughts?
Its not that accurate. It tracks the last few miles and averages the fuel. If your on a long enough drive, the average no longer shows when you accelerated, which looks great but isn't real world info. I think of those gauges as a tool...it can be helpful but also be wrong.
 

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It may be dependent on how you configure the trip odometer. I have mine set to zero out every time I fill the tank, which then nulls out the average MPG display at each fill-up. Configured like this, it's giving me my average MPG for the current tank of gas. So, sure, if I fill up then go right out on a steady highway drive, I might get readings of 38-40 mpg. But afterwards, as I drive around town in traffic, the average MPG is going to go steadily down. I notice it seems quite easy to get the average MPG to drop, but could take quite a lot of steady-state driving to get the average back up again.

With all that said, I find that the display is usually noticeably optimistic. After I fill up the tank and see how much gas the tank needed versus how many miles I traveled for that tank, I find the display is usually 0.5-1 mpg higher than reality. Yes, there can be variation from fill-up to fill-up as to when the pump automatically shuts off, but almost every time, my calculated MPG is lower than what shows on the display. There should at least be a way to calibrate that read-out.
 

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2015 Civic EX CVT sedan
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Hi all,

My $.02. I have mine set to reset each fill up too for trip B. Trip A I have it set to reset each start. I also use a Scangauge II.

My experience shows the listed MPG ALWAYS within 1% accuracy when utilizing the same pump, same setting and stopping when the pump shuts off. I fill up when nearly completely empty each tank. I find that incredibly accurate. My lifetime MPG is 39.6 US MPG. Gotta love Fuelly.com and my '15 EX CVT sedan.

Cheers!
 

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1.8 R18z1 Manual Turbo Sedan: 32.4 50/50 in-town/highway. All highway 37mpg. Cooler weather my 50/50 stays around 35mpg and all highway creeps on 39 w/ cruise control. Mine has been calculating accurately.
 
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