Sam

The silence being the diagnostic detail rather than an absence of information is not how I was thinking about it. I had been treating "no click" as "no clue".

Both effects are real, both are far too small to notice, and the reason to care about tank level is neither of them.

Weight. A 50-litre tank of petrol is about 37kg. On a 1400kg car that is under 3% of the mass, and you are comparing full against half-full, so call it 18kg — about 1.3%. The rule of thumb is roughly a 1% economy change per 2% mass change in mixed driving, so the honest figure is well under 1%, and it is zero at steady motorway speed where aerodynamic drag dominates and weight barely matters. You could not measure this without a test track.

Evaporation. Sealed since the 1970s. Fuel vapour goes into a charcoal canister and is drawn into the engine and burnt. The vapour is not lost, so there is nothing to save. Whoever told you that is quoting a real phenomenon from an era when tanks vented to atmosphere.

So question 1: technically yes, practically no. Question 2: the mechanism exists, the loss does not.

They are genuinely different, and the difference is that an alternator is a maintainer, not a charger.

An alternator is designed to replace what starting the car used — a small amount — and then run everything electrical while holding the battery topped up. It puts out a roughly fixed voltage and it is happy doing that all day. It was never designed to refill a deeply discharged battery, and it does that job badly.

A proper charger is different in two ways that matter. It steps through stages: a bulk phase at higher current, then a lower absorption phase held for a long time, then a float. And it takes hours in the later stages deliberately. Those slow final stages are where the last 20% of capacity actually goes back in — the part that decides whether the battery starts the car on a cold morning in February.

So your friend is right about the mechanism and you are right that it worked. Driving got you most of the way. It did not get you all of it, and the last part is the part that ages the battery if it is never completed.

The thing that actually works for grating ahead, and I do this weekly:

Grate and freeze, not grate and refrigerate.

Spread the shreds on a tray, freeze until loose, then bag them. They stay separate, they keep for months instead of days, and they go into a sauce or onto a pizza straight from frozen with no thawing.

The reasons it works: the drying that ruins refrigerated shreds is dramatically slower at freezer temperatures, and freezing does not hurt melting cheese in any way you would notice. Hard cheeses take this best — a cheddar or a gruyère is unchanged. Soft and fresh cheeses do get crumbly, so those stay as blocks.

One caveat: freezing does make cheese slightly more crumbly, so it is worse for eating cold on a board and identical for anything melted. Since you are batch cooking, that is the trade you want.