MPG improved with heavier tires???

[tragusa3]

Our F150 came with the stock P rated, SR-A Wranglers.

I didn't think they were as bad as most people claim, but if I needed new tires, why not try to eek out some improvement? So I debated going with another P tire or an LT. I ended up going with the Michelin Defender LTX M/S in an E load range.

From all of my research, I was expecting a bit stiffer ride, which I have now experienced and appreciate. I was also expecting to lose roughly 1 mpg due to the heavier tire. I stayed with the same size.

However, after 3-4 weeks, what I'm getting is about a 1-2 mpg increase on my work commute and a 4mpg increase on highway driving. A recent trip from Greenville to Gatlinburg (through the mountains on I40) I returned with a 23.5 mpg average on the truck computer (which is confirmed accurate).

What's going on? Could the quality of tire make that much difference? Less rolling resistance? Is the tire a different diameter and throwing off the computer? Whatever the case, I'll certainly be happy at around 23mpg on highway trips.

BTW, love the tire. Handling and noise are noticeably improved.

[tragusa3]

I finally had a chance to research the specifications on my old tire and the new. They both have an outside diameter spec of 32.1". According to manufacturer websites, they are exactly the same.

Note: I am noticing bigger hits on mileage when city driving.

[tragusa3]

Understood, but I've driven the truck for 32k miles and have never before gotten this mileage.

[IDoMyOwnStunts]

It's not just summer gas. Changing seasons bring warmer air, which is less dense and can be moved out of the way easier. Even just the transition from wet to dry roads can really help mileage. The list of things that affect mileage is enormous. It'd be really hard to pin your mileage improvement down to any single thing.

[tragusa3]

Good point. Actually, it probably did time about that way. I have noticed about 1.5mpg from summer gas. But that wouldn't account for the total of what I'm seeing.

[GoPackGo]

One thing you gas engined guys need to remember is that you will get worse mileage with winter gasoline as opposed to summer gas.

So MAYBE it's possible you timed it just right and got summer gas right when you got the new tires ???

[GoPackGo]

I have a read a few other posts from folks that put on Michelin Defenders and then thought they saw a MPG increase.

I just put a new set of them on my F350 dually 4x4. My first tow seemed to confirm what they noticed. I admit to not keeping MPG records but anytime I get over 12 mpg while towing my fiver I take notice. And my first tow was over 12. I fulltime and will watch to see what happens the rest of this travel year.

[IDoMyOwnStunts]

Tystevens wrote:
Seems very unlikely that any tire could change mpg that much (particularly on a truck, where tires are not a great source of resistance compared to the aerodynamics and weight). I mean, my brother's Pruis lost a few mpg when he put different tires on it. I suspect there is another issue causing the calculations to be off.

I lost about 1 mpg freeway when I put LTs on my '11 F150.

It's common that a high mpg vehicle like a Prius (or my Volt) will lose a couple of mpg when tires are new, especially low rolling resistance tires. After the tires wear in, mpg improves. It's far more noticeable on fuel efficient vehicles than it would be on a truck.

[tragusa3]

I'm asking questions, not making claims.

[Grit_dog]

You should get together with the guy who is getting 2 mpg better by changing out good syn gear oil for new syn gear oil. You could have 6 mpg with new tires and 3 qts of 90W and have the only 25 mpg eco boost out there....

[Bedlam]

Tires will make a mileage difference. In an extreme case example, I have an off-road toy that is also street legal. When I run low pressure aggressive tread tires verses road tires, I have less top end speed and acceleration with the low pressure tires even though both are about the same height.

[Tystevens]

Seems very unlikely that any tire could change mpg that much (particularly on a truck, where tires are not a great source of resistance compared to the aerodynamics and weight). I mean, my brother's Pruis lost a few mpg when he put different tires on it. I suspect there is another issue causing the calculations to be off.

I lost about 1 mpg freeway when I put LTs on my '11 F150.

[BenK]

Roll resistance is different between these two class of tires, even for
the exact same model/size/tread/etc

A Japanese firm was recently fined and is losing lots of market share
due them being found out that they over inflated the tires of test vehicles
used for agency certification testing....mainly MPG

The OP's title and others comment are common. In that only look at a
few of the attributes and are out of context.

It is the whole that the performance comes from...not just one or a few items

[Bedlam]

I suspect that higher inflated truck tires will give better highway mileage than the passenger car tires, but the additional weight of the truck tires will give the same or worse city mileage. This is assuming you actually have same tire diameter and tread type.

When I went from 245/75R17 tires to 275/70R18 tires, the diameter increased resulting in in difference of indicated speed and distance. When I compensated for the difference, I saw a slight decrease in city and tow mileage but no difference in highway unloaded mileage. When I went from 275/70R18 tires to 245/70R19.5 tires, the diameter did not change. I saw slightly better highway unloaded and towing mileage and no change in city mileage.

[IDoMyOwnStunts]

When I updated my F150 from P rated tires to E-rated, I didn't notice any change in fuel mileage. What I did notice, though, was my speedometer was suddenly off by 2 mph at 60 mph when compared with my GPS even though the tires were the same size. It was previously right on. That told me the new tires did have a slightly different diameter. Have you checked your speedometer for accuracy? It could affect your odometer.