hey guys so I have a 2003 2.0L mazda3 LX automatic it’s fot 175,000KM on it, the tank holds about 54 litres plus you can squeeze an extra 2-4 litres. I usually would get around 450-500KM per tank no matter what kind of driving I was doing, now it’s gone down to 350-400 per tank. Can’t notice anything obvious that would be affecting it. I read that sometimes o2 sensors could be the cause, also read that it can be a good idea to unhook the battery and reattach it when the seasons change?. If anyone has any ideas or things I could try on my own I’d really appreciate it, also my overdrive doesn’t engage anymore. I SHOULD MENTION I HAVE HAD IT TUNED UP RECENTLY ALSO SEA FOAMED IT 8 MONTHS AGO