Alternator failure and mpg (V6)

[Katka]

A couple of weeks ago we went to Monmouth for a couple of days. Whilst there the Battery Charge light came on, so I guessed the alternator wasn't well. Before leaving for home (150miles), I charged the battery to the max and switched off all power drains and crossed fingers. All was well until the M4 roadworks just before M25 when there was a huge jolt through the 'van but nothing else. I was worried and got off the M4 and towards Old Windsor where the speedo and rev counter went to zero and soon, so did we.... RAC did a fine job lending a battery and following us home.
I got a replacement Alternator from Automotive Japanese Spares in Coventry and had it fitted locally last week. The surprise to me is how much more economical the 'van now is and a bit more responsive too. At the weekend we went to Devon, mixed roads there and back, and the mpg has improved from 18/19 to 26mpg - that's on lpg, so a petrol equivalent of about 31.
I'd noticed a gradual deterioration in mpg over the last year or so but didn't know there's a connection to alternator health: Seems there is. Worth checking if you notice your mpg going down

[Bob]

Thanks.

That's interesting.