I confirm that you can go into your list of Android apps and locate the aCar unlocker, and reinstall it to unlock the Pro setting if you migrate to a new phone.
Having shared that ... I am among those that are disappointed with Fuelly for throwing those of us that are active Pro aCar users to the curb and forcing a subscription upon us. Not for us, this app would not have been so appealing to Fuelly to purchase in the first place.
Some options that would have likely sat far better with us would have been:
1) End of life to aCar Pro. No further development. Continued ad-free experience. Introduction of newer version of "aCar" with a license/usage model that was ad-supported or subscription based ad-free.
2) End of support for aCar Pro users, continue to get updates, no support unless you are a subscriber.
3) Maintain the existing Pro tier for a one time fee. Develop value for Premium subscription tier to entice people to subscribe; graphical reporting, raw receipt scanning, etc.
Personally, I could live with any of those three and not feel as bitter as I am with the current phase out plan of ad-free by mid-2020.
I like aCar. I don't want to look for an alternative. However, I also do not like the prospect of having to deal with advertisements sent to my phone when I use the app unless I pay up. It feels like ... extortion ... since I have no option to maintain a non-recurring expense experience like I used to enjoy as a Pro user.
I'd be fine just being on a stand alone aCar Pro app that I had to manually back up. there is nothing that fuelly has added to this once great app that I need. I understand servers and development costs money, but throwing a bunch of obnoxious ads at users is a sure way to lose said users. Throw me in the group looking for something else. I have no idea what or where my donation ID is, fortunately I also bought the Pro Unlocker on the play store so can still get at that and use the app at least for now.
I'll never understand the logic of trying to scam users that already paid to pay even more. It will rarely pass or pass in such a small percentage it's negligible. If we already paid for subset of features you can ask us to pay for something you developed new but not for already paid features. It's insane.
Either limit us, old Pro users, to "old features" or give us some brutal discount on the subscription. The same model I already saw on so many occasion but nobody did what you are doing. Yes you are pro but nonetheless we will kill your pro in 2 year time and push you ads. I would rather pay some other solution two times more then accept this ultimatum.
Phone died perma-dead Saturday. New one arrived yesterday. This evening went to install aCar and sync everything up. I somehow found a copy of the Pro unlock on my SD card (yay me!), but had to jump through some serious hoops to get it to sync up with the fuelly servers. And since I'd started seeing that sync, I'd stopped doing manual backups. Last backup I could find was 3 years old and only of a car we don't own any longer. Finally got it going, but it was not easy.
Now I'm wondering if I should just find another app. I already paid my dues to use this app, and I resent being told I will have to pay again.
I've also noticed more and more apps are going with monthly or annual fees instead of a one time charge. Bovine excrement!
I am upset, as well. At first, I thought aCar Pro (which I bought in 2013) was the same as Premium, so I thought there was some mistake in asking me to upgrade to Premium. Also, my app says I have the free version, but I have the features of the Pro version. The documentation does not seem to distinguish between Pro and Premium. I found my Pro Unlocker in My Apps in Google Play, so the record is there, but my app wants me to upgrade to Premium, not to Pro, so the documentation I found in the FAQ section of Fuelly doesn't match my situation. I agree with others above that this is a shoddy business practice, and should be corrected. We paid for an ongoing service, and that service should not be reduced without compensating those who paid for it.