Gas Mileage

[aolson]

I just got new tires on my 2002 ll bean outback(this is when it seemed
to start happening). I used to get 27-28 mpg on the highway and around
18-20 mpg in town. Now i am lucky to get 18 mpg on the highway and 14
in town. The tires are the same tires that were on the vehicle and the
car has around 57000 miles on it. Any ideas why the sudden severe drop
in mpg?
Thanks,

 

[Edward Hayes]

Same tire or same size & model? I doubt tire pressure could account
for that much difference but check them anyway.

 

[paul]

I had a similar problem with my WRX only I changed over to a different brand
and type, but same size tire. Gas mileage immediately dropped by 15%. I
think it was due to the fact that the new tires were "stickier" and had a
greater rolling resistance than the OEM's. Also even though they were
supposed to be the same size, there may have been an actual difference in
the overall diameter. Are your tires literally the same brand, model, size,
as what you just took off?

 

[Rick Courtright]

the overall diameter. Are your tires literally the same brand, model, size,
as what you just took off?

Hi,

Even if they ARE supposedly identical, 'tain't always so! I had a set of
OEM Michelins once that went ~84k miles. Replaced them with the SAME
tire (I thought! Only visible difference was country of origin--Michelin
builds tires in a lot of countries, maybe materials vary from plant to
plant?) Same car, driver, driving conditions: they barely went over 40k
miles! Oddly, gas mileage remained almost identical.

Like most here, I've seen pretty wide variations in fuel economy when
switching brands, styles and/or sizes. But since the OP's using the
same "everything," I'm wondering out loud if maybe he replaced his tires
about the time his area went to "winter" gas, which I think we all agree
doesn't return the best economy????

Rick

 

[hippo]

Only other thing I can suggest is if he got a *really* dodgy wheel
alignment at the same time and the front end walks like Charlie Chaplin!
Cheers

 

[QX]

Hi,

Even if they ARE supposedly identical, 'tain't always so! I had a set of
OEM Michelins once that went ~84k miles. Replaced them with the SAME
tire (I thought! Only visible difference was country of origin--Michelin
builds tires in a lot of countries, maybe materials vary from plant to
plant?)

Would you post the countries of origin and which had the better
mileage? TIA

 

[aolson]

Thanks for all of the replies.
I apologize but I don't that much about cars in general but as far as I
know the tire model, size, etc was all the same and is the same tire
from what I can tell on the vehicle now. I am not sure if the tire
came from another country or not but if it did, what do i do about it?
I would love to get back to my 27-28 mpg as this car is now no better
than a lot of SUV's and was one of the main reason i purchased it.
I have had the car for about 3 years and was fine before i switched out
to these tires.
If it were the alignment wouldn't the car pull one direction or the
other or how do i tell? Would you suggest getting them aligned again?

 

[bigjim]

You have a problem other than tires bud!!!! I lost 1-2 mpg after
swapping OEM bridgestones for Kumho KH-18's . Kumhos are good in the
rain and snow so mpg loss is no biggie

 

[S]

Hi aolson, All!

Any ideas why the sudden severe drop
in mpg?

I'm inclined to agree with BigJim, you have something else besides new
tires happening. A change of 10% might possibly be attributed to the
new rubber, maybe, _maybe_ 20% if you switched tires at the same time
your favorite station switched to the oxygenated fuel. But you're
talking more like 40% here.
No CEL? No gas smell? No trips to the local track? ;-)
27-28MPG highway is fairly typical for an OB, 18 is not.
How many tankfuls of gas have you run thru with the mileage coming out
that low? If only the most recent one, suspect bad gas. Or numerical
errors . . .

ByeBye! S.
Steve Jernigan KG0MB
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101

 

[Edward Hayes]

How do you measure your gas mileage?

 

[aolson]

Thanks again for the responses.
I have probably run upwards of 15 tanks with this kind of mileage. I
put about 600 miles on it this weekend and got between 19-21 mpg. I
don't have one particular place i fill up I fill up here or there.
How i calculate the mpg is each fill i set the odometer to 0 and on the
next fill take the amount of fuel i placed in the tank and divde that
miles went by the amount of fuel consumed. Is there a better more
accurate way of doing it?
What other things could cause the sudden loss in gas mileage do you
think that I could check or is it best to bring it to a mechanic to
have them take a look?
Thanks again.