Lower MPG with new tires

[mclasser]

I installed General Altimax RT43 tires on my Accord back in January. I've put on 3000 miles since then and while they ride nice, I've lost about 2 MPG in fuel economy since the day of installation.

I consistently drive the same roads, maintain proper PSI, hand-calculate MPG and fill up at the same Mobil and Shell stations as always. Maybe winter fuel had a small part but we're on summer blend now.

Shouldn't the tires be broken in by now? Anybody else notice an MPG loss with new tires?

 

[SirTanon]

New tires generally have softer rubber than the older tires they are replacing. As a result, they exhibit more rolling resistance than the old tires. Also, new tires have taller tread, which means more give than tires with very little remaining tread. Again, more rolling resistance.

Also, depending on who put the tires on and their general process, the tires may have been underinflated compared to your old tires, which can slightly lower MPG. I generally slightly overinflate my tires by a few PSI for this exact reason.

 

[WyrTwister]

Try 40 psi of air pressure .

Also , you are also traveling a tiny bit futher down the road with new / taller tires . Everything else being equal .

But Low Rolling Resistance tires next time .

 

[supton]

I recall seeing a drop with RT43's. Decided I didn't care.

 

[mightymousetech]

The new tires are just a higher rolling resistance than your previous set. Were the previous set the OE tires? Sounds like just a step down in quality.

 

[mclasser]

Originally Posted By: mightymousetech
The new tires are just a higher rolling resistance than your previous set. Were the previous set the OE tires? Sounds like just a step down in quality.

The previous set was V-rated Kumhos (non-OEM). These RT43s are T-rated; maybe that plays a role in MPG...?

 

[Dorian]

My MPG might have dropped about 1.0 mpg versus the very hard Michelin Harmonys that the Generals replaced. However, I will take the MPG loss, far superior wet weather traction, and cheaper cost ANY day of the week.

 

[WobblyElvis]

Went from Low Rolling Resistance tires to new Michelin Defenders. Lost a minimum of 3 mpg on the highway. I checked the speedometer before and after with a GPS to see if the new tires were larger. The new tires were if anything smaller, so that's not the reason. Sometimes there is a big difference from one tire to the next. The new tires are much quieter.

 

[E150GT]

I have noticed that tires weight is all over the place. When I was looking for tires for the mazda from one brand to the next there could be a difference of 3 pounds per tire. Not sure how much that would affect mpg, but im sure couple that with taller tread that is softer and you have yourself some appreciable mpg loss.

 

[benjy]

tyre weights vary + being unsprung weight makes it VERY important. my new in 2001 jetta had low rolling resistance mich tyres, the worse ever in the rain!!

 

[UG_Passat]

Originally Posted By: WobblyElvis
Went from Low Rolling Resistance tires to new Michelin Defenders. Lost a minimum of 3 mpg on the highway. I checked the speedometer before and after with a GPS to see if the new tires were larger. The new tires were if anything smaller, so that's not the reason. Sometimes there is a big difference from one tire to the next. The new tires are much quieter.


The Defenders are supposed to be Green-X or the Total Performance which is the successor to Green-X

 

[SteveSRT8]

Lost a solid 1 mpg going to new defender LTX's vs. goodyear wranglers which were LRR on our RAM.

I'll take the gain in traction any day. On a big truck LRR is a bad joke, trading wet braking performance for a ridiculously small gain in mileage.

 

[A_Harman]

Originally Posted By: SirTanon
New tires generally have softer rubber than the older tires they are replacing. As a result, they exhibit more rolling resistance than the old tires. Also, new tires have taller tread, which means more give than tires with very little remaining tread. Again, more rolling resistance.

Also, depending on who put the tires on and their general process, the tires may have been underinflated compared to your old tires, which can slightly lower MPG. I generally slightly overinflate my tires by a few PSI for this exact reason.


The new tire will be slightly taller due to not having had tread wear. Consequently, it will cause the speedometer to read slightly slow, and the odometer will register slightly less miles. Could account for about 3%, but I don't see it accounting for 2 mpg.

 

[ammolab]

New tires are also bigger in diameter...your miles (number of tire rotations) are longer than before. And calculate as fewer MPG in number.

 

[Eddie]

I have RT43s on my CX5 Mazda and when averaging 4-5 full tanks of fuel used, the difference falls into the tank to tank variability so I say no difference for me. Ed

 

[oil_film_movies]

TireRack.com has compared some tires to others, and they are about the only actual data I've seen.
Their testing shows you can get some significant differences in rolling resistance.
AltiMAX RT43 tires aren't especially good, but do beat some tires. The chart below compares it to a Firestone LRR, which uses the Bridgestone Ecopia technology low-hysteresis, about the best on the planet except for Michelin's patents for the same.

 

[miden851]

nothing new, each tire ought have different rolling resistance mainly due to its texture, thread, and weight