MPG Decrease w/New Tires

What tire pressure are you running in the new tires?

 

When you say GY Assurance, is it Fuel Max or ComforTred?
I did not see a difference between the ComforTred when I switched over to the Conti ProContact EcoPlus.
Excepting I only put the Conti up front, the dang ConforTred still going over 80k on rear. I will probably swtich all 4 out soon after holiday...

 

So what you are saying is that now you are getting 39-41 mpg? That is a bit of a drop. Goodyears were they LRR tires?
Continental tires are they LRR tires? If the old tires were LRR and new ones are not that can cause a big drop. What psi are your tires at? If under 40 psi front and 38psi rear, look at side wall on tires and increase but do not go over Max PSI on tires. See if this helps.

 

When I read your title, I was all ready to say it was nothing as a MPG drop with newly installed tires is pretty common. BUT a 20-22% drop? Seems excessive regardless of what rubber you have meeting the road.

The obvious things would be tire pressure and possibly balance and alignment.

Good Luck.

Because I'm curious, let us know how this plays out.

 

My MPGs dropped by about 15% when I installed the Conti Pure Contacts. However, my MPGs are also about 10% lower this year with my Michelin Xice2 winter tires, which are not new. I haven't changed my driving habits or fuel source, so I'm also a bit puzzled. I have loaned the car out a fair amount since summer, so maybe the car has learned other folks' driving patterns? It goes in for the 40K service in about 1500 miles, so I'll have the dealer check things out.

 

Try 40 front/38 rear when the tires are cold. You can lower the pressure a little if the ride is too rough.

 

G/Y fuel max are one of the best LRR tires. The ones you purchased obviously are not good LRR.. Check out some of the threads on this site re LRR tire comparisons. H

 

...also don't forget the article on Tire Rack.com, if you had replaced with exact same Fuel Max, you might have seen a MPG hit due to new tread depth etc. In this case we are winter, really taking a MPG hit for many various reasons. See my plot in another thread but, the MPG drops off faster below 35-psi pressure so that's one thing. Maybe by next spring you wear off some edge and see better results.

 

Use GPS to determine your true miles when calculating your mpg. That portion of the mpg loss isn't real mpg loss, it just your odometer showing less miles for the same real distance. See this article Tire Tech Information - Tire Rolling Resistance Part 3: Changes to Expect When Switching from Worn-Out to New Tires which may account for some of the things you are seeing. Please note that a 3% average total mpg reduction in a 25 mpg car could be equivalent to a 5.8% mpg reduction on a 50 mpg Prius given the same factors in the article. See related article of mine here regarding the "MPG illusion" as some have put it. Adding in slightly cooler temps even in FL, maybe lower tire pressure with the new tires and everything in the Tire rack article. Let us know how it is after the first 10,000 miles when the tires have really settled in. Sometimes a slight misalignment in the wheels with the old tires was well matched, and the new tires need time to settle to that alignment. Bald tires typically give the best mpg, but what is saving a few gallons if you wreck your car. Also keeping the pressure too high may shorten the life of the shocks and bushings, one needs to save a lot of gas to make up for the replacement cost of these. One has to look at the overall cost and not just on mpg alone.

I just got the Primacy tires myself but with winter in Illinois it's hard to say what the real mpg impact is.

 

New tires will definitely make a difference. New tires and the cold weather is a big part of the problem.

 

Thanks for all the tire pressure figures. Ive done the 40 front and 38 rear for colder driving temps and its been great!

 

I have Conti Pure Contact now on my Subaru Forester. I also noticed a 5-10% drop in mpg vs. the Geolanders I had on before. Thought it was strange. Hopefully, as tread wears a bit I see better gas mileage? The Conti's are supposed to have some type of formulation which saves gas.....quite the opposite.

 

Versus the Geolanders when they were brand new or when they were old and worn? As stated above, new tires nearly always drop fuel economy unless the new ones are vastly more fuel efficient. It's common to see a 10% drop in FE even if you replace with the exact same model of tire.

To the OP, The PureContact is pretty fuel efficient for its class. I'd look for other reasons for your mpg loss, like cold temps, air pressure, weather, tire size difference etc..