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.

I would imagine it's similar to pushing a loaded wheelbarrow with a soft tire compared to pushing one with a hard one. I put Defenders on our Rav4 (not LTX) and we really like them too.

I also get better gas mileage using the SHELL Gasoline for some reason...Roy Ken

Your new tires, higher air pressure = less rolling resistance.

It's possible that the tire diameter is a tad smaller and you're covering the same distance, but it's showing more miles on the odometer, hence it looks like you're getting better mileage. Not unusual for tires labeled the same size to actually measure a bit difference in diameter.

Tread pattern, tread compound all play a role. Unless you know for certain the tire diameters are exactly the same you simply cannot compare.

MPG improved with heavier tires??? | Good Sam Community

tragusa3
Explorer
May 14, 2016
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
Explorer
May 11, 2016
Understood, but I've driven the truck for 32k miles and have never before gotten this mileage.
IDoMyOwnStunts
Explorer
May 11, 2016
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
Explorer
May 11, 2016
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
Explorer
May 10, 2016
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
Explorer
May 10, 2016
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
Explorer
May 10, 2016
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
Explorer
May 10, 2016
I'm asking questions, not making claims.
Grit_dog
Navigator
May 10, 2016
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
Moderator
May 09, 2016
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.