I'm sitting @ 18MPG in a 08 so your 17MPG is respectable. I drive mainly on the highway and now think I'm going to need another car for making some runs...

A mod to shut the engine off in traffic or shut down 2 of 6 cylinders on the highway when cruising would be good but.....

 

I travel 110 miles a day with just me, no cargo and the cruise on, 95 miles of it 70-73mph and 15 of it urban driving and I get a consistent 21.5. A few weeks ago I took 5 adults, one pre-teen and 2 dogs - with luggage - on a 500 mile trip on nothing but 2 lane and no cruise control at an average of 55-60 mph and netted just shy of 29 mpg.

I wonder if I'd ever get mine into overdrive if I cut 2 cylinders?! I doubt it. lol

 

My almost 130k 2002 GC Sport gets an average 18.5 combined on the overhead console readout. I drive 75mph on cruise when I can.

I think it got a tad better when I went to Michelin Defender tires. They are rated green because of their lower rolling resistance. Amazing in the wet and braking. Love the tires.

I also added a tire pressure monitoring system by Orange Electronics and keep them corrected constantly.

 

Does using Synthetic oil make a difference on millage? I use regular oil.

The best I have got from mine with probably 85-90% HWY driving is 17.9MPG. Then again I have only had it for about 1 month. I drive 80KM to work daily. Plus it's winter here so the heater is always on

 

Although I use synthetic I think the mpg advantage is minimal at best, especially since the tranny is already synthetic as I believe the ATF+4 is.

 

I get about 23 in my '10. 80 miles a day, the first 40 at about 80 mph and the second 40 at about 70 mph. Little urban driving.

On the trips home, I do get 25-26 at a steady 60 on the country roads.

 

Mileage is heavily dependent on driving style. I get 18MPG constant. I only lose about 1 MPG with my snows on. Same goes for the highway. The closer to 55MPH the better for MPG. I can easily get into the upper 20's on long trips running 55-60MPH.

Tires DO make something of a difference. The lower resistance tires can help you pick up 1-2MPG.

 

FYI on the Green Rating (Rolling Resistance) for the Michelin Defender tire. A Fantastic tire. I am a tad aggressive in my driving. I do realize its a mini van with a transmission that should be pampered but I do drive her kind of perky.

It did give me at least 1 MPG.
They claim it will brake better and it does in a panic stop I can testify.
Fantastic in the Rain.
General Handling is noticeably improved.

As far as the ride its very nice but the rolling resistance I believe comes at a small cost making it a tad harsher on items like a running over a broom stick @ 25mph.
I have noticed on the everyday road defects near my home that I hit everyday I can feel them a just a touch more. Not by no means a deal breaker. Like I said, just on the small abrupt stuff at slower speeds.
With the 90k mile wear warranty I am documenting my rotations religiously.

 

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I suspect the added weight allowed more momentum and the 55-60 mph help reach that 29mpg.

I generally drive in the fast lane so am always over 60mph. I will try to keep her around this range and test her out. As for my driving style, I am somewhat aggresive but with this GC I do use the cruise control often, again, over 60 mph.

Thanks for all the feed back.