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'17 Summit V-6, Poor Highway Gas Mileage

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6K views 40 replies 17 participants last post by  MDBones 
#1 ·
Had a '15 V-6 Summit (2 wheel drive) for 2 1/2 years and put 26,000 miles on it. I drive between Houston and Austin (380 miles round trip) about every third week. My gas mileage averaged a low of 23.9 and a high of 25.2. Have made the same trip in my '17 V-6 Summit (2 wheel drive) three times and the best mileage I've gotten is 21.6. Same roads, same speeds, same driving habits, etc. The EPA Highway estimate on the '15 Summit was 25 and the '17 Summit increased to 26, so I thought the gas mileage would at least be the same if not a little better.

Anybody else experienced this?
 
#3 ·
The initial thought would be the Eco button. Was it on/off in either vehicle? That button actually makes a pretty big impact in the gas mileage. I would also say check your tires to ensure they are not under/over inflated.
 
#5 ·
I always drive in the Eco mode. I actually checked a few times during the last trip just to make sure. I always keep my tires inflated two pounds higher than what's recommended. What's interesting is that the recommended pressure on my '17 model is 36 for the rear tires and 33 for the front tires. My '15 was 36 for all four tires. Maybe I should keep all four tires inflated the same on the new one????
 
#7 ·
I would keep all 4 tires inflated to the same Psi. Unless you're running two totally different sets of tires/tire sizes front and back then there is no reason to have diffeeent psi.

The breaking in of the engine is a good point as well. Could get better as it's more broken in
 
#17 ·
Just to give you my very recent experience (New years road trip).

2015 Summit. V8 5.7 - 4WD

I drove from North Jersey to Charlotte, NC then I drove back a few days later. I averaged 21.5 mpg on the highway both times. I had the ECO mode off because my car vibrates when the 4 cylinders get turned off so my car is much smoother without ECO.

In other words, your V6 2wd was getting the same gas mileage as my heavy summit 5.7 - 4WD with ECO mode OFF the entire trip.

600 miles, 10 hour drive each way.

Tires were inflated perfectly to 36psi. I used 91 on the way there. 93 on the way back. but the different octane levels had no effect on mpg. I also got an oil change 1 month prior.

It was me, my GF and 2 very tiny dogs. All of our belongings were very light.

There is a lot of talk about tire pressure on this thread, but the focus should be elsewhere. Your tire pressure is either all the same, or different front and back but you are so close that it shouldn't make a difference of about 6mpg.
 
#18 ·
Just to give you my very recent experience (New years road trip).

2015 Summit. V8 5.7 - 4WD

I drove from North Jersey to Charlotte, NC then I drove back a few days later. I averaged 21.5 mpg on the highway both times. I had the ECO mode off because my car vibrates when the 4 cylinders get turned off so my car is much smoother without ECO.

In other words, your V6 2wd was getting the same gas mileage as my heavy summit 5.7 - 4WD with ECO mode OFF the entire trip.

600 miles, 10 hour drive each way.

Tires were inflated perfectly to 36psi. I used 91 on the way there. 93 on the way back. but the different octane levels had no effect on mpg. I also got an oil change 1 month prior.

It was me, my GF and 2 very tiny dogs. All of our belongings were very light.

There is a lot of talk about tire pressure on this thread, but the focus should be elsewhere. Your tire pressure is either all the same, or different front and back but you are so close that it shouldn't make a difference of about 6mpg.
Tire pressure has a lot to do with it. ACC does too. Those 2 things can account for 7 mpg, easy. Also the speed you drive.
 
#25 ·
Interesting topic. I have '16 75th Anniversary. On my trip from South FL to South CA, I was getting 28~ mpg ( I calculated it myself I was really getting 26). On my way back from South CA to South FL, I averaged 21~ mpg (both the dash and my calculations both rendered the same). I did notice more wind on my way back home to South FL. It was also colder. I would say about 10-20 degrees colder. My PSI fluctuated from 38 - 41 or so. Depending on where I was at. Kind of interesting how depending on which direction I was heading I always got lower gas milage while heading east.
 
#27 ·
Wind can make a big difference.

If there was no wind on either trip, have you checked your engine air filter for obstructions? One guy found a tech's nitrile glove stuck to his from a recent shop visit. Stuff happens.
 
#28 ·
I'm having similar issues with my 17 Trail Hawk. I drive with eco mode on, maxing out at about 60 - 65 mph in fairly smooth traffic, and I can't seem to hit anything about 20 - 21mpg. Typically, I'm averaging around 18! That's a far cry from the 25 I should be getting.

Is there a way to tell if my Jeep is in 2wd or 4wd? The way I understood it is that it will be 2wd until it senses slippage, and then it will kick over to 4wd.
 
#33 ·
My 14 Overland with the GY Forteras was 36psi all around. My 16 HA with Bridgestone Ecopia's says 33psi front, 36psi rear. Not sure why they changed it but I always run 36psi all the way around.

I have about 7800 miles on my 16 3.6L HA now. I've never checked pure highway mileage but my 50 mile round trip to work has been averaging 21.7mpg combined. I think that's pretty good for the mix of highway, freeway and in town stop'n go that I have. That's at least 1-2mpg better than I was getting on my 14.
 
#35 ·
I dunno. It sounds like the Ecopia's weren't the only tires with a psi change. I think the Ecopia feels more comfortable and handles better than the Forteras I had on the 14.
 
#41 ·
I suppose one of these days I should check mine. That's what I currently average combined on my work commute... consisting of 60mph highway, 75mph freeway and stop'n go city driving.
 
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