as an aside, there are "apps for that"...
There's a lot of them but I will stick my neck out for an Android one I've been using for years:
"Fillup 2.1.1". There's an old version on FDroid that works on older phones and up ...but..the latest is version 2.1.4 for android 10 but I haven't tried it.
Fillup 2.1.1 has been trouble free, ad-free and doesn't ever seem to phone home according to my firewall...has logs,graphs and database is easily exported as .csv files for each vehicle.
It's most useful if you fill your tank at every fillup. You can keep track of many vehicles.
It's interesting to see variations and how much gas is used over the years total mileages ...you can make notes per gasoline type and oil changes too...you can "reject" wildcards from the average..ie: accidentally emptying the tank or whatever.
There's a lot of them but I will stick my neck out for an Android one I've been using for years:
"Fillup 2.1.1". There's an old version on FDroid that works on older phones and up ...but..the latest is version 2.1.4 for android 10 but I haven't tried it.
Fillup 2.1.1 has been trouble free, ad-free and doesn't ever seem to phone home according to my firewall...has logs,graphs and database is easily exported as .csv files for each vehicle.
It's most useful if you fill your tank at every fillup. You can keep track of many vehicles.
It's interesting to see variations and how much gas is used over the years total mileages ...you can make notes per gasoline type and oil changes too...you can "reject" wildcards from the average..ie: accidentally emptying the tank or whatever.