Petrol Gauge question

[SubaruFan]

Morning folks. First post here, although I've followed the forum for several years

I have a question - why does my petrol gauge go down, especially after a long journey, and then pop back up again a few days later, generally at random. I know its not using petrol, and it's not a problem, I'm just curious. It's a Subaru Outback.

Thanks,
Ewan

[Gilbertd]

Older cars just used a float to drive the petrol gauge directly but a lot of modern ones have a float but it is tied in with the trip computer. It takes a reading, the trip computer works out how much fuel it has used and sets the petrol gauge accordingly. This prevents odd readings if you park on a slope for instance. Every so often, or in some cases, when you open the petrol filler, it has another look at the float level and resets itself which is what yours is doing.

[4eyes]

My 2011 outback does the same. I think the level shown by the gauge is calculated by how much fuel the ECU thinks has been used via the petrol injectors etc, it doesn't realise it's actually using lpg instead, so shows what it would expect until the float sensor contradicts it, or its reset after switch off. Tis normal.

[SubaruFan]

Thanks, thought it must be something like that.