Do miles per gallon decrease over time?

I just heard about a government sponsored bill that will give a rebate if you buy a NEW car that gets at least 4 miles per gallon more than what you currently own. That’s great, except that I own a MINI cooper and I want a Honda Fit. My question, that I’ve posed to my congressman, is: “Is this according to a new version of each car? Or, rather, am I comparing what my old car gets now and the new car?”

If the latter is true, is there any formula for how miles per gallon may get worse as a car ages?

Thanks, anyone.

Your Mini doesn’t qualify. That’s a good thing, why should the government (us) pay for something like that? Here are some points from, the web site describing the program:

Your vehicle must be less than 25 years old on the trade-in date

Only purchase or lease of new vehicles qualify

Generally, trade-in vehicles must get 18 or less MPG (some very large pick-up trucks and cargo vans have different requirements)

Trade-in vehicles must be registered and insured continuously for the full year preceding the trade-in

You don’t need a voucher, dealers will apply a credit at purchase

You should READ the actual program and its terms before you post stuff like this. Your Mini Cooper does not qualify, period…

In addition to agreeing with texases 100%, I would like to add that, in my opinion, your fuel economy should not decline as the car ages. I suppose if you gain weight, add heavy accessories, or something like a roof rack, your fuel economy might decline. It might also decline if your driving habits change or you begin to drive more aggressively. Otherwise, it should be relatively consistent throughout the life of the car. If your fuel economy drops as the car gets old, it is either because it hasn’t been properly maintained or it is in need of repair.

What Is Obvously Needed Is More Information From The Politicians Who Think Up This Stuff.

I always think to turn to politicians when it comes to car advice of any kind, after all they’re the ones running major car companies. Could your congressman clarify something for me? Gas guzzling clunker A is 5 years old, is driven 6,000 per year and gets 16 MPG. Gas guzzling clunker B is 6 years old, is driven 9,000 miles per year, but gets 18 MPG. Considering that a huge amount of energy (and resources) go into the production of a replacement car C, which gets 25 MPG, how long in months would it take to “break even” on total energy consumption should I decide to replace Clunker A? Clunker B? I want to know when my “carbon footprint” starts to get smaller or isn’t that what I’m trying to do? Maybe it’s energy independence.

By the way, will he get one of those cool Lee Iacoca Mustangs as a perk, too? Sweet!


CSA, if you haven’t already seen it, I think you would enjoy this

Actually, a well-maintained car will frequently deliver somewhat better gas mileage as it ages.
My Outback’s average mpg went up somewhat after ~60k, and the mpg increased even more after ~90k. Your experience may vary, as the saying goes.

1992 Explorer. 140,000. Same mpg as ever.

I think that one of the best reasons to log your gas mileage with each fillup is that declining gas mileage is usually the first hint that something needs to be fixed.
Gas mileage often improves as the engine breaks in and stays there until a problem, like worn out rings or leaking valves comes along.

texases is correct but add…

the purchased car will be $45,000 or less
The traded car will be scrapped, stripped and will be worthless.

I am not sure if this credit which is up to $4500 will be in addition to the traded value or not. I doubt it will since the gov might consider that double dipping.