EVIC MPG How does it work?

[sdm197]

Hi,

My theory was that it just continues averaging all the journeys until you reset it. That is what seems to happen on mine 300C (Diesel) In the UK fuel is $12 per gallon.

When I just poodle around town with no long journeys, I get around 27-33mpg, on any kind of run 50miles or more set at cruise (70mph) I will get 43-45mpg after a reset. When I don't bother to reset the EVIC it does begin to rise again from the 27-33 but I seriously doubt that it would get back up to 40mpg. If it is over a tank of fuel, lets say its saying 27mpg, then I do a longish run, then it will go up again to around 38-40.

Does anyone know how it gets the mpg?

SDM197.

[Super T]

It's not the whole trip... I let my RT get 12,000 miles on the trip and it would still fluctuate by 2-3mpg between a week of city driving and a 300-mile roadtrip. If it was the entire trip, 300 miles would have barely been enough to change it a tenth or two. I'm not sure anyone ever posted exactly what period of time it averages over.

[FloridaRT]

That's why I reset mine every time I fill up......................

Bob

[formerice]

I have the EVIC on my Hemi Ram, and I believe that you need to reset every tank. When I fill up , it seems to read high for a few miles then settles down to be quite accurate over a tank. The Ram weighs 6,000 lbs and is very sensitive how you drive, Cruise control on flat roads I can get very close to 20 mpg. If you drive it like a hybrid= shut the motor off at every red light, never warm up, or let it idle, it's very economical, if you honk on her , it's horrible. I would think that the computer is calculating fuel flow against distance traveled?

[Orange Crush 375]

I never reset mine. More interested in mpg's for the life of the car. Currently at 1800 miles I'm at 14.5 with 95% city and 5% highway.

[MikeEast]

I figure it's almost 'real time' (like GM does it) for about 30-45 seconds and then goes into 'averaging' mode. I use it a lot for 'testing' on my little stretch of GA20 two-lane.

Mike

[stitchmonkey]

I never reset the time unless I go on a dedicated road trip like Ohio's LX&Beyond. I also never reset estimated mpg only trip miles A & B. I think the computor estimates by the time engines running idle etc. and fluid measurement in the tanks? On my rod trip when going up small rises in a road or sharp turn my mpg dropped due to fuel switching tanks or just plain moveing away from the sensor, as soon as everything leveled out mpg reading go back to normal.

[justdeb]

I do sometimes look at the MPG.
But I keep track of miles until empty more often than MPG.

[Graygoat]

I reset mine at every fill-up, but I've found it's not accurate. When I figure the mileage with a calculator using the same numbers it's seeing ... # of miles and # of gallons used ... it's always off.
The Chrysler Laser XE I had back in 1985 (!) had the trip computer and the MPG was always dead-on. One thing I've noticed is that, even after accumulating 200 miles on the trip and having an average MPG already established, if I get into it hard I can watch the MPG drop quickly. But, if I do the opposite ... be very easy on it and on the highway ... I'll drive for miles before I see the MPG go up even .1. There's no way a single incident of stomping the pedal would actually drop the average MPG to that extent with an average that's established over a 200 mile trip.
In other words ..... I don't trust it, nor do I go by what it indicates.
(The damn thing's too dim anyway!)

[Graygoat]

Update on how accurate the EVIC MPG is .... did you know it will continue to drop after you turn the ignition off?! I just noticed this yesterday. As long as you're on "retained accessory power" the MPG will drop. I find that extremely weird, since the computer would be seeing no ignition pulse or fuel flow in this state. Just what does this thing use to calculate the MPG it displays?!?!?!