Does a higher output alternator give better fuel economy?

[Angry Possum]

Oddly today, a good friend of mine is getting better gas mileage on his 2012 Ford Fusion 3.5 Liter engine since he replaced only the Alternator with a high output Alternator. His alternator was originally week for a month or so and he was getting real bad fuel economy, till he changed it today because his battery died.... Is this possible, and this is all he changed?

He found this out from his onboard fuel computer in the car, as he went from 10 mpg originally on the older alternator, to 19 mpg now with the new higher output alternator. I shit you not. This is very weird indeed.

If so I'm thinking of getting a higher output Alternator for my 93 Ranger 4.0l. It's due for one soon.

 

[fastpakr]

19 sounds totally normal, so the question is why he was getting 10 before.

 

[Angry Possum]

19 sounds totally normal, so the question is why he was getting 10 before.

He doesnt understand either, he didn't change anything but the high output alternator. Before this, he was going to change his fuel pump and injectors. But didn't. It's a good thing his alternator crapped out. Or he would of done both the injectors and the fuel pump.

 

[rusty ol ranger]

He don't understand, he didn't change anything but the high output alternator.

10mpg from a fusion?

Thats what my 460 F250 gets.

I wouldnt bet it was the alternator that made the difference. Maybe his old one was so weak it was throwing the ECM off?

Either way a good regular output would of fixed that too.

 

[Curious Hound]

Switching from a HEALTHY normal sized alternator to a high output alternator would not do that.
However, if his original alternator was not working properly and voltage was fluctuating and often lower than it should be, then any number of vehicle systems would have been functioning improperly and possibly causing the low mileage. The 10mpg was bad and likely caused by electrical issues. The19mpg is in the realm of normal.

 

[Angry Possum]

Switching from a HEALTHY normal sized alternator to a high output alternator would not do that.
However, if his original alternator was not working properly and voltage was fluctuating and often lower than it should be, then any number of vehicle systems would have been functioning improperly and possibly causing the low mileage. The 10mpg was bad and likely caused by electrical issues. The19mpg is in the realm of normal.

Yes most likely, I just didn't know putting in a healthy alternator would bring his mpg back to normalcy. I found that odd and yet interesting. The previous posts makes sense with especially with reference to the ECM I suppose.

 

[Angry Possum]

10mpg from a fusion?

Thats what my 460 F250 gets.

I wouldnt bet it was the alternator that made the difference. Maybe his old one was so weak it was throwing the ECM off?

Either way a good regular output would of fixed that too.

Interesting

 

[00t444e]

Oddly today, a good friend of mine is getting better gas mileage on his 2012 Ford Fusion 3.5 Liter engine since he replaced only the Alternator with a high output Alternator. His alternator was originally week for a month or so and he was getting real bad fuel economy, till he changed it today because his battery died.... Is this possible, and this is all he changed?

He found this out from his onboard fuel computer in the car, as he went from 10 mpg originally on the older alternator, to 19 mpg now with the new higher output alternator. I shit you not. This is very weird indeed.

If so I'm thinking of getting a higher output Alternator on my 93 Ranger 4.0l. It's due for one soon.

Onboard fuel MPG readout means nothing, they aren't accurate, hand clacluleted MPG is the only way to go. If the alternator was going bad low voltage can cause all kinds of electrical issues.

 

[RobbieD]

Since I put a lightning rod on my Ranger I've been getting 832 miles per gallon with a 2.8 auto.

It does make the radio reception suck, though.

 

[gaz]

@Angry Possum ,
Yes, yes a larger alternator can definitely improve fuel economy but only when aimed correctly and the moon is out. You buddy clearly had the moon window open and failed to notice.

 

[Lefty]

Oddly today, a good friend of mine is getting better gas mileage on his 2012 Ford Fusion 3.5 Liter engine since he replaced only the Alternator with a high output Alternator. His alternator was originally week for a month or so and he was getting real bad fuel economy, till he changed it today because his battery died.... Is this possible, and this is all he changed?

He found this out from his onboard fuel computer in the car, as he went from 10 mpg originally on the older alternator, to 19 mpg now with the new higher output alternator. I shit you not. This is very weird indeed.

If so I'm thinking of getting a higher output Alternator on my 93 Ranger 4.0l. It's due for one soon.

I wouldn't know about all this, but if should get a new alternator, get an uprated voltage regulator too. They are not expensive and can be be installed in no time.

 

[Angry Possum]

Onboard fuel MPG readout means nothing, they aren't accurate, hand clacluleted MPG is the only way to go. If the alternator was going bad low voltage can cause all kinds of electrical issues.

His car actually ran a lot better also. It's not just the gas mileage.

 

[bobbywalter]

He inadvertently corrected the bad connections in the swap.

There must have been a ground issue on a sub system since it was starting okish.

Bigger alternator would use more energy if you were using it.

 

[sgtsandman]

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.

 

[Bgunner]

If the bushings/bearings in an alt are going bad this increases the amount of force needed to turn the armature in the alt causing a drop in fuel efficiency. Usually when an alternators bushing or bearings are going bad there is a noticeable sound coming from it to let you know there is an issue.

Is this the case here? Most likely not due to no mention of noise but I am adding this as a reason why a bad high mileage alternator can decrease fuel mileage.