2019 REX gas tank capacity coding needed?

I am from California, just bought a new 2019 REX as I was told gas tank capacity restriction was removed since 2017. Fill up the tank first time but the gauge only showing 70 miles in 4 full bars. If it is 2.4 gallon i should be getting 85 miles plus in the gauge. Anyone here with 17-19 REX get the same issue? Do you need to code it to expand to full 2.4 gallon?

First thing to understand, is the REx engine doesn't drive the car's rear wheels. You can't figure 'mileage' by saying the REx engine gets X miles per gallon, so I should get X times 2.4 equals Y miles on 2.4 gallons. The REx engine runs a generator, with the sole task of keeping the high-voltage traction battery charge at around 7% (uncoded) while you drive, for the electric motor to draw on. The car's computer looks at your last 20 minutes or so of driving, how many kilowatt hours of electricity you used to cover X miles, counts on its fingers and toes, and 'guesses' that the generator can provide Y kilowatt hours on 2.4 gallons of gas, and that should take you Z miles under your current driving style/conditions. It all hinges on your last 20 minutes of driving 'style', AC or heat on, Comfort or Eco mode, ambient temperature, high-speed/highway, etc. And with a new car, it may take the computer a few more miles and days of driving for it to 'learn' your driving habits, before it starts giving accurate guesses - I wouldn't worry about seeing super-accurate ranges in the 'guess-o-meter' until you have a couple of hundred miles on the car. But the rule is, if you drive it like you stole it, your range will be less than if you drive it like your grandma.

The 2019 can use all of the fuel out of the box in the USA. THe original restriction was a CA issue where the gas assisted range couldn't exceed the pure EV range to get certain credits and perks (with the HOV lanes). With the increases in battery capacity, that's no longer an issue. FWIW, effective REx assisted range seems to be in the 35-40 mpg...IOW, not all that much. It wouldn't surprise me that the computer won't actually let the engine run dry...it tends to mess up the fuel injectors and fuel pumps that get lubricated from the fuel, so there's probably a little bit more gas in there that can't be used, regardless. The stated amount is the useable amount.

Actually your right you can get 80 miles from a tank!

Generally speaking the gauge does show a bit low from what you'll actually get. While the mileage is calculated math from the processor - how your driving does not have a whole lot to do with it because the engine runs at a some what fixed rpm and load regardless of what you're taking from the battery. i.e. if the car is pegged it's not going to run over its designed set rpm.

A safe estimate is 30-35 mpg or an average of 80 miles. Since you don't want to run it dry you should plan on refueling after 60 miles on newer modes which use the full 2.4 gallons of fuel.

Regards - Mike

From what I've been told, BMW tends to use a fuel pump that is lubricated by the fuel going through, so you don't ever really run the tank dry...it stops prior to that to preserve the pump. IOW, you shouldn't hurt the thing if you do run it dry.

jadnashuanh said:

From what I've been told, BMW tends to use a fuel pump that is lubricated by the fuel going through, so you don't ever really run the tank dry...it stops prior to that to preserve the pump. IOW, you shouldn't hurt the thing if you do run it dry.

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The fuel pump is indeed lubricated by the fuel flowing through it. However, it's cooled by the fuel it is submerged in. It's never good on a fuel pump to run without it being completely submerged. This can have a significant impact on reliability and pump life.