Better MPG with age and miles

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My in-laws gave my daughter their 1996 Mercury Villager, 3.0 V6. They purchased it when it was about a year old and around 30k miles. Currently, it has 237k miles. Prior to the 100k mile mark, they averaged 20-21 MPG. Afterwards, it is getting 27-29 MPG. Not sure why. I drove the vehicle from their house in SE Colorado to my home in South Dakota. Still runs and drives great. Inside is pretty immaculate. My Father-in-law was always a Ford man since his early teens. Now 72, he recently purchased a Nissan Rogue. Convinced only because his Villager was a rebadged Nissan.
 
I've seen a few cars get better mileage after say 10k. I've seen some high mileage cars start getting a couple of mpg better as the coolant level goes down, right before a head gasket lets go. My sons saturn got phenomenal fuel mileage( 3mpg over most sc1 manuals), and a really worn cam lobe was found on teardown.

I am having trouble with the 8 mpg increase you describe, nothing about that makes sense. Thats a huge increase. Are the tires stock? Smaller tires would throw off the odometer and your mpg calculations.
 
It depends on how it's driven. They might have short tripped it while it now sees higher speeds and longer distances.

The mpg display on my grandparent's Trailblazer sometimes says <12 mpg, because sometimes all it sees is 2 mile trips to the grocery store and back. But if I were to drive it I would probably get high teens in it since I drive 70+ miles everyday, lots of highway.
 
Stock tire size. I will go to fueleconomy.gov and see what this vehicle is rated at. But I filled the tank and tracked the mileage myself.
 
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Maybe it's so loose, internal engine friction is nearing zero
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20-21 was their average over a very long time and different driving conditions. They have owned this vehicle for twenty years. The long distance driving was one trip by me under varied and sometimes hilly terrain. They kept the vehicle so long because it was getting such good MPG. They were well aware of the changes in MPG, it wasn't just me who experienced it.
 
Originally Posted By: Ducked
I get better mileage as I get older, because I don't drive so fast.


This, also it's not horribly uncommon for something in a car to go bad and it increase gas mileage. There is always a side effect but a lazy o2 or even a old TPS can go bad and tell the car its going slower then it is resulting in slightly less amount of fuel being used.

Eight mile per gallon extra is rather high. I took our old 95 Regal to Iowa a couple of weeks ago. Car averaged 31.5 miles per gallon vs its normal 27 highway. I think a lot of this had to do with the car already being warmed up after it ran for an extended period of time more then anything else tho.
 
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It has the most to do with the nut behind the steering wheel, and driving habits. Then maintenance including tire pressure.
 
My '08 Accent keeps getting better gas mileage as the miles rack up. Maybe at 155k miles it's broke in finally?

Currently getting 41 mpg and the oil consumption too has nearly stopped from a quart every 5k to no need to add at 5k miles. EPA estimated average is 29/32 mpg.

 
Originally Posted By: andyd
Are you using e0 vs e 10?


This.

I've found e0 vs e10 makes a big difference, especially with older vehicles that were designed before e10 was a major factor. My Jeep gets 16 mpg combined average with e10 fuel. The few times I filled up with e0 gas, I averaged a solid 18-19mpg doing the same kind of driving. Ethanol has less energy potential per gallon than pure gasoline does.
 
FWIW, I posted a thread with this very topic years ago.
I do think that fuel economy continues to improve with miles in a well maintained, mechanically sound engine.
I've seen this with various cars we've driven north of 150K.
I suspect that wear reduced ring friction over many hours of operation.
It would be interesting to hear from others who've kept cars from new out past 100K or so.
 
Better tires? Better gasoline (higher energy content)? More highway instead of city?

Usually E10 is thought of as bad, but does it burn any cleaner? I mean, if it keeps deposits down, might the engine run a bit more timing? Not beyond ECU limits of course, but less apt to ping in the first place.

Any chance that it't lighter due to parts rusting off?
 
Originally Posted By: fdcg27
... It would be interesting to hear from others who've kept cars from new out past 100K or so.
My Mazda didn't get near its best mileage until about 7k miles. It was still about the same (around 50 mpg on good days) at 600k.
 
I've discovered that the air filter housing has holes and that air is bypassing the filter. Perhaps unregulated air flow is contributing to better mileage (?). I have plans to fix the housing with tape this weekend.
 
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