Why does my 2008 Prius get 3-4 mpg better mileage than my 2004?

Fresher battery pack?

Has the (Tranny) oil been changed?

 

there are so many little things on a prius that can affect mpg's. how many miles on each?

 

Lots of possibilities!

For years, I maintained high speed automated 200 ton presses (625 strokes per minute). We had a row of five "identical" presses. Every one of them behaved differently.

 

You could swap battery packs between those 2 cars to see if that’s the difference. Plus doesn’t the 2008 have better battery’s to begin with?

 

i had an '04 and an '08, didn't notice any difference in mpg's.

if you think there is drag, pull the wheels, inspect the brakes, hubs, bearings and etc.

 

The '08 is 4 years newer?

 

So many in fact that this really is not a reasonable question.

One could substitute ANY make of car for the Prius's in his question......and the answer would be equally as elusive.

The answer: Because they are not the same car.

 

Pretty easy to figure out.

If the hybrid battery is original in the 2004 and still working good it would be a miracle.

A Prius is only as good as the hybrid battery. If the battery is not contributing alot of power then the bulk of the power demand falls on the anemic little 90 horsepower motor.

Signs of early retirement are the hybrid battery goes to purple bars real fast like in a fast food pickup lane and once it has purple bars it will not recover to blue bars very well.

 

I agree with everyone here.
Basically you're only looking at two factors here, actual age of the vehicle and tires/tire pressure.
And there are so many other factors that can make a difference.

Really, it comes down to how satisfied or unsatisfied you may or may not be with your 2004's performance. That is now a 14 year old vehicle so what could cause a difference becomes hard to pinpoint.
Could be aged Hybrid Battery.
Or could be the operational decline that comes with any machine that has been in service for 14 years.
Or the combination of both.

 

Software came to mind. I new a guy who had two 2008 and the newer one didn't get the mpg the first one did.
I don't remember the numbers he quoted.

 

some people are mistaken about that because the epaulet changed the testing protocol between the two years and the monroney numbers changed, but not the car

 

Does someone else drive the cars other than you? That could also be the reason

 

So transaxle fluid change likely hasn't been changed.

Probably neither here 'nor there; just for the record.

I agree with that.