filled up tank, mileage read 489 drove around neighborhood maybe 5 miles. looked down, mileage now reads 453. what happended? also, sometimes I get 500 miles on the tank fill up somewhere else, can read 490. why?
it's a complex mathamatical formula that is trying to estimate how many miles you have to empty based on past driving habits and current gas levels. it's not perfect.
Are you referring to 'Distance to Empty'? If so, it is just an estimate, based partly on your recent mpg history. But short term mpg varies wildly depending on changing conditions that the car cannot predict. Climbing hills guzzles fuel rapidly. And mpg is always pathetically low when the engine is cold, but the car doesn't know how many engine warmup cycles you will have during a tank. So the displayed 'DTE' is not 'accurate', but merely a reasonable guess that displays inconsistencies that cannot be explained without detailed mile-by-mile knowledge of changing fuel use. I rarely use it, and then only as a rough guide. If it is much larger than the next driving segment, no worries. If it is somewhat similar, or even 25% higher than the next distance, then the fuel level needs to be monitored carefully during the trip, and don't skip the last gas station before a long stretch without service.
