Actual vs Computed

[fusionTX]

I thought I'd start a topic on actual vs computed miles to see how the car computer compares with actual gallons pumped. I just filled my first tank since I started tracking on Fuelly, and will provide my input shortly.

I do think, for my first tracked tank, the computer was optimistic by about 1.5 MPG.

 

It will be interesting to see how if we can come up with a trend.

[gadgetguy]

I thought I'd start a topic on actual vs computed miles to see how the car computer compares with actual gallons pumped. I just filled my first tank since I started tracking on Fuelly, and will provide my input shortly.

I do think, for my first tracked tank, the computer was optimistic by about 1.5 MPG.

 

It will be interesting to see how if we can come up with a trend.

Great thread fusionTX the last couple tanks have had me scratching my head.

[jeff_h]

I don't know if there's a trend to me found, but possibly. My display says 48.4 and manual calc via fuelly is 46.74 so mine is a bit off... though I've seen others on here stating that theirs were spot-on the same.

 

But I would expect most to be off by a tad -- my Prius and 2010 FFH were both about 1.5 MPG optimistic on the display, so this 2013 FFH is just following suit, from what I've seen thus far.

[fusionTX]

Here are my tank's computed stats.

 

Surprising to me is the low MPH. Less than 25 MPH. Most of my driving is highway, but I guess since I started taking the backroads home from work ( speed limit 35 MPH ) and all the sitting at lights that comes with that, really lowers the average MPH.

 

The computed MPG average is optimistic by 1.6 MPG. I should say that the first click at pump agreed with the gallons shown. I always go three clicks total, which added an extra half a gallon. I really don't have any issues filling my tank unless it's at an old gas station.

 

 

Actual pumped gas

 

 

My Toyota Camry also tended to be optimistic with its computer. I think most cars are. I will continue to track this and hope others do too.

 

Overall, I am very happy to have gone over 500 miles with the tank. I went 21 miles beyond DTE 0. The red icon showed up when DTE was 2 and computed gallons used was 11.5. That is two under total capacity. I wonder if red icon always shows up when car thinks there are only two gallons left.

Edited May 24, 2013 by fusionTX

[corncobs]

Ok here are my current stats screen shot from the gas cubby app.

 

 

My personal lifetime average (avg. on all the screens) which equals the miles on the pic above is 38.7 MPG; so it's only off by 0.7 MPG.

The ladies lifetime which has never been reset sits at 38.5 MPG

[fusionTX]

I don't know if there's a trend to me found, but possibly. My display says 48.4 and manual calc via fuelly is 46.74 so mine is a bit off... though I've seen others on here stating that theirs were spot-on the same.

 

But I would expect most to be off by a tad -- my Prius and 2010 FFH were both about 1.5 MPG optimistic on the display, so this 2013 FFH is just following suit, from what I've seen thus far.

You have a lot more data than I have, but we are both about 1.6 MPG off, which is not terrible if you think about it.

[gadgetguy]

I'll be filling up again tomorrow or Saturday so I will post my results.

[acdii]

My flex is only .4 MPG off. Right now lifetime is sitting at 21, and actual is 20.6. The 10 Fusion is sitting at 41.8.

[hybridbear]

To date our computer Lifetime Average has exactly matched the Fuelly computed average or has been off by .1 MPG. Be careful comparing individual tanks to the gallons on the pump. Different gas pumps can be slightly inaccurate. Sometimes I've put less in at the gas station than what the car says I've used and other times I've put in more gallons than the car says I used. Overall it has been very close. Going forward I will be trying to include in my Fuelly notes the gallons the car says I used in addition to my EV miles per tank. If others do this too then we can see over a longer time period how accurate the car's trip computer is. I expect it will be off somewhat because the fuel use is likely only measured at one injector and then multiplied which will cause a discrepancy to actual fuel used.

 

Another item of note, most of us cannot get more than about 11.5-12 gallons in no matter how low we go, as has been noted in the other thread, on the C-Max Hybrid Forum they've had a similar discussion and in the C-Max it appears that when the DTE reaches zero people are putting in about 12.5-13 gallons. Some C-Max owners have even gone 700 miles on one tank with a tank MPG around 53-55 MPG which means they're putting in a full 13 gallons when their DTE reaches 0 miles. This is an interesting discrepancy.

[gadgetguy]

Today's fill up was right on the money and I stopped when it first clicked off. You can see the details on my fuelly account and here are a couple pics.

 

Computer

 

Actual

 

This is also my best mpg on a complete tank not just a trip. Keeps getting better!

[mrobinso8]

I generally set my trip computer on a fill-up and do a manual calculation after 3 or 4 fill-ups. The calculated mileage is 2 mpg in the Ford Company advantage which helps them come close to advertised. Same as my 2011 Fusion gas. Apparently Ford does not think anyone can do their own calculations. My old and missed 2006 Honda Accord was spot on so it can be done. I think the calculations are programmed to be off to benefit Ford.

[fusionTX]

The thing aout stopping at the first click is that the first click can come at different tank levels depending on the pump. I prefer to fill it to the top and always do three clicks. That usually means an extra half gallon by the time the third click is done.

 

I have not read the manual, but somewhere on these forums I read that three clicks was recommended.

 

I suppose if you always use the same gas station and always stop at first click, you have a better chance of it being consistent, but I still prefer to top off.

 

BTW, mine was accurate to the first click also, but I still had half a gallon to go.

[gadgetguy]

The thing aout stopping at the first click is that the first click can come at different tank levels depending on the pump. I prefer to fill it to the top and always do three clicks. That usually means an extra half gallon by the time the third click is done.

 

I have not read the manual, but somewhere on these forums I read that three clicks was recommended.

 

I suppose if you always use the same gas station and always stop at first click, you have a better chance of it being consistent, but I still prefer to top off.

 

BTW, mine was accurate to the first click also, but I still had half a gallon to go.

I will try that the next couple of fill ups and see what the difference is.

[acdii]

I wished the Fusion tank was like the Flex. First click and its full. Any more clicks puts in ounces. I also tend to use the same pump too, rarely do I have to go elsewhere to fill up.

 

This is why Ford had a difficult time with me when the plugs fouled. They said it was bad gas, and I said, o really, then why arent the plugs fouled in my other Fusion that gets the same gas from the same pump? ;) Crickets chirped. Then they said, well, maybe you got some bad plugs. Whatever, 4 plugs out of 100's of thousands, and they were the only bad ones. Ok, go ahead and believe that Ford. ppffft. :headspin:

 

 

In any case, this is why I tend to use the same gas station when I can, and the same pump, consistent fills and accountability. :)

[fusionTX]

Here is what the manual says about filling the tank.

 

Filling the Tank

For consistent results when filling the fuel tank:

• Turn the ignition off before fueling; an inaccurate reading results if the engine is left running.

• Use the same fill rate (low-medium-high) each time the tank is filled.

• Allow no more than two automatic click-offs when filling.

Results are most accurate when the filling method is consistent.

 

Calculating Fuel Economy

Do not measure fuel economy during the first 1000 miles (1600 kilometers) of driving (this is your engine’s break-in period); a more accurate measurement is obtained after 2000 miles - 3000 miles (3200 kilometers - 4800 kilometers). Also, fuel expense, frequency of fill ups or fuel gauge readings are not accurate ways to measure fuel economy.

1. Fill the fuel tank completely and record the initial odometer reading.

2. Each time you fill the tank, record the amount of fuel added.

3. After at least three to five tank fill ups, fill the fuel tank and record the current odometer reading.

4. Subtract your initial odometer reading from the current odometer reading.

5. Calculate fuel economy by dividing miles traveled by gallons used (For Metric: Multiply liters used by 100, then divide by kilometers traveled).

Keep a record for at least one month and record the type of driving (city or highway). This provides an accurate estimate of the vehicle’s fuel economy under current driving conditions. Additionally, keeping records during summer and winter show how temperature impacts fuel economy. In general, lower temperatures mean lower fuel economy.

[DeeCee]

At 7500 miles my cars computed lifetime average is 45.3 mpg. The actual calculated is 44.0 mpg.

[hybridbear]

On the C-Max Hybrid forum someone made a great point on their thread about this...the poster commented about how gas pumps are not really trustworthy. He/she cited a news story from NJ where almost half of gas pumps have been found to be inaccurate, charging customers for more gas than is actually pumped into the car. Since the fine for gas stations doing this is only $500 per pump and the pumps are tested once a year it is easy for a gas station to make up the fine in a few months by consistently charging customers for a couple extra ounces. He/she worked at a gas station while in High School that did this, was caught, paid the fine of $500 and continued to do it because the additional money made more than offset the fine

[hybridbear]

Check out this thread about the inaccuracy of gas pumps. I am more inclined to trust the trip computer rather than the gas pumps. In MN all gas pumps are required to have a sticker showing the last time they were inspected and found to be accurate. Pumps are supposed to be inspected annually. I always look at the info on those stickers to see the last time that pump was inspected when buying gas

[GrySql]

Today was one for the books. Until now theTrip computer and the gas pumps have been pretty close.

Today, at a Costco I've used many times my fuel gauge indicated 1/4 of a tank remaining, I expected to put in about 8 gal of fuel.

So, at 7.2 gallons the handle clicked off, I did my usual and continued at low flow until it clicked off again, I usually do that 3 times. On the third low flow fill it went to 9, 9.5, 10 and finally clicked off at 10.2 gallons, 3 gallons over the first handle click-off!!

I restarted the car and the Trip computer indicates 8.17 gallons used, about 2 gallons below what was actually put in. I find that as grossly incorrect and as a result my actual mpg's are far below the Trip computer's estimate.

What am I to think of this odd occurance?

[acdii]

This is one of those things I have been thinking about ever since I got my F150. I used to fill the tank up to match what the computer said I used, which usually was the first click. My thinking is that the trip estimate of gallons used, is just that, an estimate, and eventually it will reach a point where it will take much more to fill the tank than what was reported used. It seems that you just proved that theory, I didnt have the truck long enough to find out.

 

I am filling only to first click on the new Fusion and will see how it does. I dont fill at full throttle either, just the first step on the handle lock. So far seems to be working as it is very close to the trip computer. After reading many posts regarding the filling issues, I do a slow fill so it can vent.

[GrySql]

My car has 9600 miles on it and has been very consistent about the amount of fuel put in the tank from the pump and the computer's accounting.

I have never tried to 'match' anything, simply read the results. Thus far the car and pump have agreed.

 

I too have read this forum and am always consistent in my method of fuel delivery, fill at the slowest setting on the handle, then do two additional click-offs.

Never has it taken more than 1 additional gallon for the 2 extra clicks - but 3 gallons??

Over the last 7 months of ownership I am fairly acquainted with the fuel gauge and how much to expect the tank to require.

Only on today's fill-up were the readings so far off that I could not believe my eyes.

I was hand metering the slow 3rd click fill and actually looked under the car to see if there was a leak.

If it does it again on the next fill-up I will be concerned.

[hybridbear]

My car has 9600 miles on it and has been very consistent about the amount of fuel put in the tank from the pump and the computer's accounting.

I have never tried to 'match' anything, simply read the results. Thus far the car and pump have agreed.

 

I too have read this forum and am always consistent in my method of fuel delivery, fill at the slowest setting on the handle, then do two additional click-offs.

Never has it taken more than 1 additional gallon for the 2 extra clicks - but 3 gallons??

Over the last 7 months of ownership I am fairly acquainted with the fuel gauge and how much to expect the tank to require.

Only on today's fill-up were the readings so far off that I could not believe my eyes.

I was hand metering the slow 3rd click fill and actually looked under the car to see if there was a leak.

If it does it again on the next fill-up I will be concerned.

I found the same thing. Through the first 9000 miles or so my Fuelly calculated MPG based on the pump readout of gallons used matched the car dash Lifetime Average because the car calculation of fuel used was very close to matching what I actually put in at the pump. Then all of a sudden I had one fill up where I put in about 2 gallons more than what the car showed I had used and since then every single time I've bought gas (which has been a bunch with this road trip) the pump has indicated more fuel has gone into the tank than what the car says I've used. At first I suspected that the leaking fuel module that's being recalled might be the cause of this, but the dealer claims that my fuel module isn't leaking...so now I'm perplexed. Now the car indicates .3 MPG higher for the Lifetime Summary than what Fuelly shows

[GrySql]

I found the same thing. Through the first 9000 miles or so my Fuelly calculated MPG based on the pump readout of gallons used matched the car dash Lifetime Average because the car calculation of fuel used was very close to matching what I actually put in at the pump. Then all of a sudden I had one fill up where I put in about 2 gallons more than what the car showed I had used and since then every single time I've bought gas (which has been a bunch with this road trip) the pump has indicated more fuel has gone into the tank than what the car says I've used. At first I suspected that the leaking fuel module that's being recalled might be the cause of this, but the dealer claims that my fuel module isn't leaking...so now I'm perplexed. Now the car indicates .3 MPG higher for the Lifetime Summary than what Fuelly shows

Strange that this happens almost at the 10k miles driven point. Computer mis-alignment....

I wonder if Jeff's car did this? Or, any other cars with over 9,000 miles.

I really think our early Job 1 cars need a software update for the operational OS.

 

Besides, your car and its high mileage and mine have one huge difference, mine has a loose nut behind the steering wheel.

Quirky behavior.

[acdii]

Apparently Temp does have some affect. Until today I haven't had fill issues, but today, high 80's and over 70% humidity, I had trouble putting gas in, on the slowest setting, which I normally do, it clicked off at 3.8 gallons. Huh? Then clicked off again a 8 gallons, and I knew it used more, so wound up putting in at least a gallon more than what the dash said by the time I was done. It was also raining pretty hard, and had just started to rain, so the temp had dropped from 86 to 68 from when I pulled in to when I had started pumping. Screwed with my Fuelly too. At only 1749 miles. Up until then the dash and pump matched.

[GrySql]

Apparently Temp does have some affect. Until today I haven't had fill issues, but today, high 80's and over 70% humidity, I had trouble putting gas in, on the slowest setting, which I normally do, it clicked off at 3.8 gallons. Huh? Then clicked off again a 8 gallons, and I knew it used more, so wound up putting in at least a gallon more than what the dash said by the time I was done. It was also raining pretty hard, and had just started to rain, so the temp had dropped from 86 to 68 from when I pulled in to when I had started pumping. Screwed with my Fuelly too. At only 1749 miles. Up until then the dash and pump matched.

Go figure...

Our weather has been consistent for the last two months, no real extremes. I had the Fuel Warning happen once a while back, cleared it with the funnel.

I had some Brake and Traction Control Warnings again 3 weeks ago, gone in the morning though.

 

At least I print out my VHR as each warning appears on the dashboard (why do we call it a dashboard?).

I have a file folder I keep in the car for the TSB, Recall and VHR's in, this is the first car in 55 years that needed one.

My Dealer will just love me when I show up for the 'cracking' thrust washers and show him the file.

 

It is still a wonderful car to travel in, even to the Dealer.