New tires giving me less MPG?

[Benito]

a week after buying my elantra i replaced my tires, now my dash displays me averaing25mpg opposed to 29 mpg of when i got it.
Could the tires be causing this?
(They are cheap tires, just needed to replace old ones bad and went with economy option)

[Pete03GLS]

yes. crappy tires, and low air pressure will decrease mpg's.

id check the air pressure first. and if air pressure is good... then u have some REALLY crappy tires...

[Benito]

haha yea, i trust the shop properly adjusted the air pressure but i will double check.

[Pete03GLS]

the speed rating of a tire will affect mileage. a higher speed rating has a stiffer sidewall. providing less rolling resistance. so get all teh information off ur tires n let me know.

size and speed rating, and brand name.

[SuperGLS]

Probably has to do more with the air pressure.

What brand are they?

[ricerrx7]

You should also check your mileage the real way. Divide miles driven by gallons used.

[Benito]

Yup im currently doing that, last time my trip odometer got reset so had to start over..
They are primewells ps830's, Speed rating H and a treadwear of 460. Id say just about the same as other tires...
195/60/15s stock for elantras.

[blmqzjc]

When I put new Falken Ziex 912's on my Elantra, my mpg immediately went down about 2 mpg. Now that I have about 5k miles on the Falkens, mpg is back to where it was on the OEM Michelins. This puzzled me at first, and I just assumed the Falkens got worse gas mileage. But after thinking about it, I came to a more logical conclusion:

The OEM Michelins had 43k miles on them, and mpg had been great. Reason = tire tread rapidly deteriorating and causing less rolling resistance.

The new Falkens got less mpg. Reason = brand new tires were sticky and super grabby. After a few thousand miles, that initial "tackiness" is gone.

You ever wonder why mpg on a new car improves after 4 or 5k miles? I always thought it took that long for the engine to "settle in", and I'm sure that has something to do with it. But the tires have something to do with it as well, I am now convinced.
Air pressure was closely monitored on both sets of tires, so not an issue. Also used gas from the same Chevron station.

[smileymattj]

I'm sure the shop that installed the tires put the PSI rating labeled in the door. I always go by the max stamped on the tire, or slightly higher. As long as you are not overloading your car, over inflating the tires will improve MPGs. When your car starts to squat from excess weight, it's not a good idea to have overinflated tires.

If you do decide to overinflated, make sure you know the risks involved.

[Benito]

Ok thanks guys.
I guess ill wait to see if they get "broken in" in 4k miles.
For now im really considering switching to chevron after all the good things ive heard.

[blmqzjc]

Ok thanks guys.
I guess ill wait to see if they get "broken in" in 4k miles.
For now im really considering switching to chevron after all the good things ive heard.

In addition, I sometimes (maybe twice a year) throw a bottle of Chevron Techron in the tank. That, plus the Techron that's in the gas to start with, seems to work for me.

[Benito]

Im out of luck, no Chevrons around here...i hadnt noticed because i just moved out here.
=/

[blmqzjc]

Im out of luck, no Chevrons around here...i hadnt noticed because i just moved out here.
=/

Just use a good quality top tier gas (BP/Amoco, Shell, etc) and throw in a bottle of Techron every once in a while - you'll be just fine. Most auto parts stores carry Techron around here, and some Walmarts, etc. Occasionally, I've even seen a BOGO on Techron at Advance Auto or Autozone. BTW, I always use the 20 gallon size vs. the 12 gallon, for a little more concentration in my 14.5 gallon tank

[Neanderthal]

I'm sure the shop that installed the tires put the PSI rating labeled in the door. I always go by the max stamped on the tire, or slightly higher. As long as you are not overloading your car, over inflating the tires will improve MPGs. When your car starts to squat from excess weight, it's not a good idea to have overinflated tires.

If you do decide to overinflated, make sure you know the risks involved.

NEVER trust a shop to do the right thing. ALWAYS check lug torque and tire pressure. Some shops do it right--my experience with Discount Tire and Wal Mart has been positive, they always get torque and pressure right--and some shops seem to do the Wing-And-A-Prayer method. One "specialty" shop gave me three different pressures and torque all over the place, and the torque was in some cases 20 high.

If you want something done right, do it yourself.

As for running max pressure, IMO that's not a good idea. 35 should be plenty for most apps. Just remember when tires work they heat up, so any time you go more than 5 miles your pressure is going to exceed the max on the sidewall.