zoutv

Have a 2000 SE. I do 80% city driving, so my mileage was never great. However I just got a new set of all season tires Falken ZE 329 225/50/17." I live in Boston and with the winter weather, snow storms, ice etc...I expected a bit of a decrease in mileage. But not this bad.

On a full take of premium I usually got 240mi or so. Now I'm getting about 160mi. I don't get it. The shop that put them on did an alignment and the ride is relatively smooth. The shop set the psi @ 35. This is a very stiff ride that I"m not crazy about. The (stock I think) Potenza's I had I would set psi at 33psi Front and 30 psi rear. Extra traction in the winter.

Should I set the PSI all around for 35? Harder, softer?? Something else at play here? The only other thing I noticed that seems odd is at start up. Sometimes the engine starts with a struggle. Takes 2-3 seconds to start than instantly. I also had the front driver side wheel replaced.

Niccos89

iTrader: (2)

What PSI did your last set of tires have, do you know? 35 seems a little high...
Can't recall off the top of my head, i think it should be 32 at the rear's, 29 at the front?

Engine struggling on start-up...could be alot of things, as could be the reason for such a big drop in mileage, but my first stab in the dark would be your alternator. Start there.

PadawanKnight

iTrader: (1)

I doubt the tires are the only source of your drop in mileage. They probably aren't even the main source. As far as recommended psi, it depends on the max rating of your tires. What is the max psi for your tires, and what does that psi rate them for weight?

Scottwax

iTrader: (8)

The really cold weather up north is a mileage killer. My son's Corolla has gone from 35 mpg to around 29 mpg since the cold weather hit.

foodmanry

iTrader: (15)

A higher PSI will usually give you better gas mileage to a certain point on the higher PSI.

Sounds like you have something else going on for such a big drop. When is the last time you had your tune-up (spark plugs, PCV valve, air filter, etc.)?

knight_yyz

iTrader: (40)

denser cold air needs more gasoline to keep the AFR in the proper zone. My mileage is 650Km per tank in summer, drops to 500 or so in the cold weather.

Duckhead

This is true.

Did you put on the same size tires as the ones that came off? If the diameter is smaller then that will hurt MPG as well.

zoutv

Sorry for such a late reply. The tires are rated:
-Max Pressure 350 Kpa 51 PSI
-Max Load 670Kg 1477lbs

They are 225/50/17 tires.

I just set TP for 36psi in the front and 34 psi in rear. From the numbers above, can anyone see what the problem may be?

DennisMik

iTrader: (2)

I have the same question Duckhead does... did you have 225/50/17 tires before? If you had 16 inch tires before, bigger tires make your car go faster than the speedo indicates, which means you have gone more miles than the odometer shows. But I don't think this would be the difference you are experiencing. I agree with the others that there is something else wrong.

You started the max inflation pressure is 51 psi, making 36 psi kind of underinflated. Underinflation makes the tire softer, requiring more power to make it roll. Also it makes tires wear out faster and they are more prone to flat tires when hitting a pot hole.

zoutv

Yes, I did have the 17" Potenza tires when I bought the car. They were 225/50/17" I have not had a tuneup in over a year.

Should I up the tire pressure to 40 PSI? Or 44, 45 PSI? I upped my tire pressure today to 36PSI front, 34 PSI rear. Upping the pressure that little amount made the ride noticeably noisier.

Niccos89

iTrader: (2)

40-45 PSI.....are you nuts???

nsnrider

iTrader: (59)

I agree that's too high. I set mine 32 front and 30 rear or whatever the sticker in car says, never had a problem but my mileage did take a dive this winter, going from mid 24 mpg down to low 23 mpg in combined city/highway driving. I did hear that they mix up gasoline a bit differently for cold weather which inturn decreases gas mileage on top of what others have said about the cold air.

vball_max

iTrader: (5)

I wouldnt increase it much over 35 psi. That will cause the tires to wear more in the middle of the tread than the sides. I keep mine at about 35 instead of the recommended 32 to help out with the mileage a little bit.

But the drop in gas mileage does sound like something other than the tires. I wouldnt think new tires would affect it more than 1-2 mpg.

2slow

iTrader: (6)

While you are correct that with more air, more fuel is needed to maintain the proper air to fuel ratio, this is not the reason fuel consumption increases in winter. While the air is denser, the ultimate volumetric efficiency (and power output) of an engine will increase, the amount of air (mass) needed to generate a constant power level will not vary significantly.

A real culprit is a change in gasoline formulation to increase cold weather starting. This change decreases the fuel's energy density, and therefore more fuel is needed to generate the equivalent power levels.

Although, to aid in cold starting, excess fuel is added upon start-up as the cold engine components will not aid fuel vaporization. This cause will then impact those who make many short trips (have frequent cold starts).

http://www.fueleconomy.gov/feg/factors.shtml

cajun1104

my car does the same thing in cold weather. drove to Indiana this winter while it was negative 8 or so outside. mpg went from about 24 to around 18. i run my tires at around 38 all around.

Svtperformance01

Where do you guys base the MPG from, the computer? I heard it was off by 3-4 MPG. What i dont understand, on Edmunds it says that the car has a 18.5 tank size yet I can only put almost 15 gallons on it, is it really 3.5 gallons of reserve? The highest i got was a lil over 240 miles, needle was boarder line on empty (gas light wasn't on yet). So im basically getting around 16-17 MPG (250/15 est.). This is from city only, not highway. Car doesnt get me the best mileage, it's ok, was kind of dissapointed since my Cobra give's me almost the same MPG on almost same tank size (from filling up, almost 14 vs to almost 15 gallon size). This is driving mild, not agressive nor too slow either.

maxdriver10

Cold Weather= Death to gas mileage...since winter started my MPG has dropped from 22 to 17 around town, you have to check your tires often to make sure PSI is right

Tire Pressure=Death to gas mileage...however, from what I read in your post that seems to be under control

Rolling Resistance=Death to gas mileage...are your new tires wider than your old ones? Increased tire with means more contact with the ground which means more friction which means more rolling resistance aka bad fuel economy

I run all four tires at 33 psi year round