Does a higher output alternator give better fuel economy?

[Angry Possum]

Replacing the alternator fixed other issues due to the low voltage output and possibly bad/dirty connections.

It is possible the vehicle in question has the system that partially disengages the alternator to save on fuel when the battery is fully charged. So, the alternator could have been running full tilt all the time and thus contributing to the low fuel mileage.

But that isn’t the entire answer. The above comments about low votlage to the and perhaps dirty connections are more likely to be the main culprits.

Also, as stated, the onboard mpg calculators are not accurate. They can be close but that is the best you are going to get. The one in my 2019 is consistently 1 mpg less than taking the trip milage divided by the gallons used to fill the tank. The same goes for the mpg average on my ScanGauge II in the 2011. At best, they are just a reference point to get an idea how the vehicle is doing mileage wise but I wouldn’t trust it as a reliable data point.

I get it, but his fuel gauge avg on his computer went from being a 10 to a 19. It was reading 10 with the old alternator, but after he replaced it it showed 19. That's a big jump. No?

 

[fastpakr]

I get it, but his fuel gauge avg on his computer went from being a 10 to a 19. It was reading 10 with the old alternator, but after he replaced it it showed 19. That's a big jump. No?

Absolutely, it's a huge jump. But the issue isn't something miraculous about the new alternator. It's whatever issue was caused by the failing alternator - low voltage causing ECM issues, ignition misses, etc. Or bad connections to the alternator that were resolved during the replacement, etc. The higher output on the new alternator isn't what brought the mileage up.

 

[Lefty]

Absolutely, it's a huge jump. But the issue isn't something miraculous about the new alternator. It's whatever issue was caused by the failing alternator - low voltage causing ECM issues, ignition misses, etc. Or bad connections to the alternator that were resolved during the replacement, etc. The higher output on the new alternator isn't what brought the mileage up.

Agreed. A bigger alternator is not better. It is not even necessary. It will not increase mileage or performance. If you should add an Efan or extra lights, the original stock will still keep up. But if you should want more output, just install the uprated Motorcraft voltage regulator.

 

[ekrampitzjr]

A higher-output alternator would theoretically cause more fuel consumption than would a healthy stock alternator. That's because of the extra drag on the system. The pulley on the high-output alternator is usually harder to turn.

I'm with the others here who think something was wrong and accidentally was corrected during the alternator swap.

 

[00t444e]

I get it, but his fuel gauge avg on his computer went from being a 10 to a 19. It was reading 10 with the old alternator, but after he replaced it it showed 19. That's a big jump. No?

Again those aren't accurate, what is his actual hand calculated MPG?