Strange Milage Reading

[Pitter]

I had the battery changed the other day as reported elsewhere in the forum and later filled the tank. The kilometer reading between the two circular gauges normally gives around a 430 kilometer range when the tank is topped up. Now as can be seen in the image the tank is almost one quarter down yet the range shown is 413 kilometers. About 75 kilometers back the range was reading at over 500 kilometers which I've never seen before. Also I only top up to the pump click and don't keep pumping until gas spills out. Seems whacky but at least the trip odometers remain accurate so no worry about running out of gas because of a false reading . Does this have to do with new battery installation?

 

[dunhillmc]

Because of the battery disconnect the system will have to relearn your driving style for the estimated distance. Give it a tank or two

 

[Pitter]

Great thank you.

 

[181962]

The trip meter shows only 6.9 km/L over 80 km since reset. The 2020 AWD models hold 15.3 gal. or about 57.9 liters. At that trip meter rate you'd run dry at around 400 km, not too far off the 430 km range you're accustomed to seeing.

The likely answer is less about the engine needing to reset codes and more about a ghost in the range gauge. See what the range gauge reads at next fill up.

This business about the car learning a driving style is often greatly exaggerated in these pages. Cars with electronic fuel injection have been self-tuning themselves to a degree for decades where disconnecting the battery will cause the ECM to lose its adjustments. A couple hundred miles of driving will get the codes reset but in the mean time the differences will be negligible or non-existent, certainly not a cause for a 20% increase in gas mileage. If anything, until the codes are reset a modest drop in gas mileage might be expected.

You know, that 400 - 430 km range works out to about 16.3 - 17.5 mpg. That's awfully low though I doubt that's any revelation to you. I could see getting that mileage with a lot of real city driving, not the NHTSA's generous interpretation of "city".

 

[Pitter]

Thank you for that explanation. I refilled today and the range read at about 460 kilometers so looks like it is readjusting. As to the low milage, probably due to the fact that I drive up a 13 kilometer long mountain road daily sometimes "working" the turbo to get past a slow moving truck before the next curve.

 

[181962]

Thank you for that explanation. I refilled today and the range read at about kilometers so looks like it is readjusting. As to the low mileage, probably due to the fact that I drive up a 13 kilometer long mountain road daily sometimes "working" the turbo to get past a slow moving truck before the next curve.

That sounds like a gauge issue, not an actual performance/gas mileage change.

Yeah, climbing that mountain would kill mpgs. And if the road is at all twisty where you're constantly working the brakes on the way down, you wouldn't get the offsetting benefit of a lot of downhill coasting.

Here's a tip you also probably don't need. Going down the mountain, braking for a few seconds then releasing/coasting then rinse and repeat might get you more life out of the brake rotors. Riding the brake down will get them very hot and prone to warping.

 

[Pitter]

Yes endless curves. There are about two straight stretches long enough to pass something slow moving but that's about it. The difference in milage climbing my mountain road and occasional flat highway drives is amazing!

 

[181962]

Yes endless curves. There are about two straight stretches long enough to pass something slow moving but that's about it. The difference in mileage climbing my mountain road and occasional flat highway drives is amazing!

That'll do it. In my normally aspirated 2.5L, if I were to drive tankful in real city driving, nothing I expect to ever do, I'd expect mid-to-high teens mpgs. Country roads and expressways get me typically 31 - 33.

In the end, I'm thinking your view is priceless.

 

[Pitter]

Ha ha yes indeed it is.