Due to the recent coronavirus lockdown, my car hasn't been getting the mileage it's been used to.
For reference, it's a 2007 Mercedes E280, with the 3.0L 6-cylinder turbo-diesel & 7-speed tiptronic.
The battery is only a year old - the original having lasted 12 years. In normal circumstances where it gets a decent couple of hours' run at least once a week if not a lot more, there is no issue at all.
Since lockdown, it was at first getting no more than 15 minutes every couple of weeks for a stock up at the local supermarket. Six weeks of this & it was flat. I live right next to a garage, so getting it jumped wan't a problem.
I've since determined that I need to run it at least once a week to keep it happy. For this particular exercise I'm not particularly interested in fuel saving or efficiency, just a 'best practice'.
What's the best method to get a 'reasonable' charge into it every week?
Options, as I see them…
- Idle it for 30 mins [650rpm]
- Play half an hour's stop-start on roads with traffic lights & junctions with periods of artificially hard acceleration off the lights [4000rpm]
- Find somewhere I can pootle along at 30-40mph constant [1000 rpm]
- Run it up the motorway
a. at its normal 2000rpm it does at 80mph
b. artificially drop a couple of gears & rev it at 3000 or above
In short - is it the revs or simply the duration that is going to do the job? Will it charge 'better' at high revs or am I just wasting fuel for nothing?
After comments; A mains charger is not an option. I live in London. I have absolutely no way to park the car anywhere near the house or any electricity supply.