Of course you get it every 90 days exactly - that's what it's programmed for. This is done with a microprocessor that knows the date and time, it's not a clockwork device that loses time
Make sure you switch it on after draining so that it registers the low level before you refill it, otherwise you'll waste your time.
And bear in mind that this is done for a reason. Modern fuels containing a lot of biofuel are not stable. You risk a reduction in the ability to withstand knock etc.
It's not coolant, it's refrigerant.
It's illegal to refill a system that has lost refrigerant without first attempting to rectify the source of the leak (Fgas regulations).
However, all automotive A/C systems have a natural leak rate from the hoses and joints that can't necessarily be improved...
I disagree that a gallon of petrol will take you more than 30 miles, particularly at any speed which is what you're likely to be doing if you're beyond PHEV range.
I agree that it's not worth doing at 70p/kWh in the UK - UNLESS your goal is CO2 minimisation rather than economy, time etc
You won't get better airflow, if you did then Mitsubishi would have done it.
Yep, if you have twice as much filter area, it will take twice as long to get dirty (provided airflow is evenly distributed, which it won't be), but probably at twice the cost. If you can get a bigger area filter for...
You can clone TPMS sensors so the car won't know the difference.
You can also program a 2nd set to the car, but you have to tell it which set you're using (eg summer and winter wheels)
It cannot start without the relay - that's the point. Under any circumstances. A vital part of the circuit is missing. Simple as that. That's why removing it, rather than having an easily accessible bypass switch, is not the best idea.
It's no different to removing the starter motor or solenoid...