[Lway2014]

Just purchased Ram 2500 with 6.4 Hemi and Highway MPG according to Computer is 19.7 and when driving well in city with a bit of rural driving my best has been 16. Only 1 thousand miles on vehicle.

Anyone else having such luck?

 

[Badunit]

Anyone else having such luck?

No. I have seen high 18's at 45-55 mph but I believe this would really be 16 mpg when hand calculated. Still pretty darned good but my highway average is closer to 13 (hand calculated) when not loaded or towing anything. Highway = 75mph which tends to reduce the mpg pretty badly.

You should try hand calculating it to see how accurate it is.

 

[oilbelcher]

remember the evic computer only tracks the most recent 200 miles. it will not track back farther than that. can't even track a full tank of gas. it typically overstates MPG. also, it is human nature to remember the "best of" values, but forget the moments where the MPG was really terrible. you need to hand calc over multiple adjacent tanks to really know, and average out the ups and downs. the adjacent tank tracking eliminates error due to the gas station pump shutting off inconsistently.

 

[DetroitDoc]

remember the evic computer only tracks the most recent 200 miles. it will not track back farther than that.

Where did you get that from? My "a" trip computer has 1,150 miles on it and shows 18.4 MPG. My "b" trip computer has 367 miles on it and shows 17.9 MPG.

If the MPG calcs only included the last 200 miles, both my "a" and "b" trip computers would show the exact same mileage. Based on the empirical evidence, that 200 mile theory is wrong.

Doc

 

[nailem]

I think oilbelcher is talking about the "average MPG" display not the ones on your trip. those are really impressive number. is trip "a" an all highway?

 

[DetroitDoc]

I think oilbelcher is talking about the "average MPG" display not the ones on your trip. those are really impressive number. is trip "a" an all highway?

Nope "trip A" is 50/50 city/highway. I live in the metro Detroit are so these aren't rural city roads. There are stop lights once or twice a mile and traffic is moderate.

I took a picture of this evic this morning. If I remember I'll post it up when I get home tonight.

 

[RamSportsPower]

I think oilbelcher is talking about the "average MPG" display not the ones on your trip. those are really impressive number. is trip "a" an all highway?

Even the average miles display is not limited to 200 miles only in my opinion as I always reset trip b and average miles at the same time and their numbers are always the same after 200 miles.

 

[DetroitDoc]

I was able to resize the image on my phone to be able to upload it. Here's my evic after 1,132 miles of 50/50 city/highway. I'm extremely happy with the MPG!

I'd say I have a light to moderate foot. I'm not a "hyper miler" by any means. Normal accelerations are between 2,000 and 2,500 a RPM. I probably hit 4,000 once a day merging into heavy traffic or passing someone. I probably floor it once every couple days.

'14 crew cab, 6'4" bed, hemi, 8 speed, 3.92s...

 

[huntergreen]

i was told not reset the evic for mpg and the more miles driven the more accurate it will become. i use my dollar store calculator and keep a log if i want an accurate mpg figure.

 

[oilbelcher]

The evic trip calcs don't track the same set of miles. I don't recall what an old thread said, but it was something like 200 most recent miles for one trip, and longer for another, for some reason I recall 500-1000. I reset A after every tank, and I have never reset B. The 200 does seem to be about right for my A, as it moves much more quickly than a full tank of fuel ( 500 -550 per tank since I have diesel). I still reset out of habit, but it does not track well with my hand calcs. This makes sense, 1) due to less accurate than consistently tracked hand calc, and 2) evic trip A is tracking less mikes than my reset.

Now trip B, never reset in over 5000 miles, since new, move more slowly than trip A, but far too fast to estimate lifetime. This validates, based on my tracking, that it is tracking the most recent set of rolling miles somewhere between 500-1000 miles.

Our trucks are not capable of tracking lifetime miles. Others have confirmed, and my religious hand calc tracking verifies this.

Once I learned this, I no longer pay serious attention to evic. At best, it's a crude trending tool, over recent miles.

If you are serious about knowing and tracking MPG (not everyone is), you MUST hand calc over adjacent tanks.

 

[oilbelcher]

A suggestion to the moderator, can we have a sticky for examining evic mpg methodology vs hand calc. I would suggest it is limited to methodology, not for everyone to post their mileage. That could be a separate thread. It seems that every couple weeks a new thread pops up on MPG, and the same comments get repeated. It is confusing, because it is easy to believe the evic is more capable than it is.

Just as a reference, there is another thread on the diesel forum that is dedicated to tracking hand calculated MPG, and evic figures are not allowed to be posted. That eliminates the threads "I rolled down hill today and got 99 MPG, here is the pic to prove it!"

 

[Badunit]

I hand calculate my mpg and it's nothing near these high numbers. And my EVIC, which is about 10% high, isn't near those numbers. But I'm glad to see others getting fuel mileage that good.

 

[DetroitDoc]

The evic trip calcs don't track the same set of miles. I don't recall what an old thread said, but it was something like 200 most recent miles for one trip, and longer for another, for some reason I recall 500-1000.

That's the silliest thing I've heard in a long time. No software engineer is going to use one algorithm for trip A and a different algorithm for trip B.

Also you don't need to keep track of every data point to keep a long term average. You simply need to know that you have a 18 mile per gallon average over 10,000 miles and you are going to average in 6 mpg over 100 feet. You don't have to keep 10,000 miles of data points. So it would actually be more work for a software engineer to build in some artificial limit to the number of miles it can track over.

I can pretty much guarantee you that the trip computers absolutely do not use a rolling set of miles. That would make associating fuel economy to a trip computer completely pointless.

I'm not saying there isn't accuracy issues with the evic tracked MPG. I'm simply saying that they don't use a rolling set of miles. Also even if the evic has accuracy issues, which I'm sure it does, it's a good way for people to compare mileage to each other.

P.S. I'm a software engineer.

Doc

 

[oilbelcher]

I agree there is a lot of confusion around car MPG tracking. I track very closely and have proven it is not accurate (no surprise) and it does not track lifetime average. It doesn't. I don't don't why. I have a thread elsewhere with a spreadsheet print out showing why evic doesn't track lifetime average. I have never reset since new, and the lifetime average floats around based on latest driving conditions. This means it is tracking only recent conditions.

I really wanted to rely on evic, but we can't. It is designed to track recent MOG conditions, and not long than this.

The engineers could have done anything they wanted, and not sure why they set this up this way. Most likely because other brands do similar.

I do not know its exact programming, but many of us can prove it doesn't track lifetime average or anything close.

 

[oilbelcher]

My Mercedes and acura were similar to Ram; I tracked every gallon pumped out to three decimals of accuracy, over the life of those vehicles and it indicated 1) it was not accurate, 2) always higher than reality, and 3) didn't track over the life of the vehicle.

I stopped looking into differences between trip A and B and determining exact rolling miles, as it is not accurate enough for me, and does not track cumulative performance.

I am the minority in that I want precise MpG tracking. For most it is fine, but understand its limitations.

 

[DetroitDoc]

Doh! I'm embarassed I even made it more complicated than it needs to be. I was just out mowing the lawn and thinking about it.

Wen you hit reset on the trip computer it resets the variable tracking the distance to 0. It resets a variable that tracks fuel consumed to 0. During driving it obviously increments the distance driven. It also increments the fuel consumed since the ECU knows exactly how much fuel it is injecting into each cylinder. Then each time the display is updated (probably 30 times a second or so) it divides the distance by the fuel consumed and displays the MPG.

Again you can see there would be absolutely no reason it would be calculated over a rolling set of miles. It would be extra work to add that logic in. And who would do a bunch of extra work to artificially introduce a crippling restriction?

Again I'm not saying the evic is accurate. I'm just saying the average is the average over the trip distance. It does not use a rolling set of 200 miles.

As to why the evic might be inaccurate, there is are two possibilities. The first is variance in injector flow rate which could be caused by anything from slight differences from injector to injector, differences in fuel pressure regulator, fuel pump and fuel filter efficiency. The other variance might be a purposely introduced optimistic fudge factor to improve the ownership experience of those who do not hand calculate.

I have't hand calculated yet but I plan to. For those hand calculating, it's not the panacea you probably think it is. Pumps are notoriously inaccurate... A Study in Michigan found...

From 2010-2012, 56 percent of inspected pumps dispensed slightly more than labeled, 23 percent gave less, and 21 percent were accurate. The worst offender, a station in Monroe County's Carleton, dispensed just 2.4 gallons when the pump stated five gallons during a test in 2011. See a searchable database below.

Also note that even the pumps that are deemed accurate are allowed a +/- 1.2 cubic inch per gallon variance.

 

[oilbelcher]

I reset A every 500 to 550 miles, with fuel up. B has never been reset. Not even referring to accuracy, my trip A MPG floats around based on recent conditions. I have followed it closely. For example, my first half talk is all highway from a weekend trip, and A will show 28-ish, then as I enter my weekly work routine, where I get 23-ish, my trip A quickly drops and by the end of the tank, it is reflecting only my city driving routine. This means it is tracking less than 500 miles, otherwise trip A would be in between 28 and 23.

I took a long trip all highway, and after a hundred miles, my Trip A shot up, but trip B (never been reset) also climbs, but not as fast as trip A, but climbed far too fast to track lifetime.

Agree that gas stations can of some inaccuracy, but they are also regulated by law. Car companies are not.

 

[ItsMeKO3]

I've got a 1500 but when I got gas today I checked my mileage and the computer was off by about 2 mpg compared to hand calculations. I reset it and I'll check it again in a few days.

 

[cass]

i've got a little over 4200 miles on my hemi sport....its gotten 18.8, 19.3, 18.3, 18.1, 18.0, 17.0, 18.2, 17.8, 17.7, and 18.1 for an overall average so far of 18.1. the last two results were on a trip to upstate n.y. from southern maryland....overall, i'm pleased. i use it to commute on a 110 mile round trip that is mostly 4 lane and little traffic and speeds of 60-70 most of the time, when i'm not riding my motorcycle. all are hand calculated miles driven and gallons put in. btw, i love this 32 gallon tank.

 

[gazingm42]

While only have my 3500 with the 6.4 Hemi a short time with about 1000 miles I getting much less. However the biggest factor I have is living in the Mountains and
living at higher elevation. So I know I will get much less MPG than some other flat landers