I don't know about optimal, but I can hit the NRC estimated average mileage of 5.7 L/100km when doing 110 km/h (Roughly 68 mph), so that's really all I care about. Any slower then that and you're just being annoying when on the highway.

 

slower has less wind resistance, so it should go up as you slow down.
We ran my wifes 2.4L on a all highway trip with cruise set at 73MPH and it made 38 Mpg (not the computer)

 

Drove 58 miles from Augusta to Barnwell at 55mph on cruise control and got 42 MPG (No A/C on) after just filling up

 

Averaged 35mpg running 70mph from Buffalo, NY to Greenville, NC with 4 people and luggage in the car. That is hand calculated not the computer.

 

Wow! Those are some killer mileage figures! And as an average? Whoooweeee! Here in SoCal, if you drive 55 to 60mph you'll get run over! People here are crazy! 80 mph avarage 70-75. Yeah, as mentioned the faster you go the more wind resistance and the harder the engine has to work to push you through the air. Thats why the Toyota Prius is most efficient around town and not on the freeway. Just the opposite of what a gasoline engine is.

 

Actually, that's not why a Prius is efficient around town. Prius will use more electrical power when driven at slow speeds, and under correct driving conditions, use all electric power with motor shut off.

 

Its all about throttle control. You need to squeeze gently into throttle and speed up going down hills so when you go up the next one you can allow it to slow down and use your stored momentum. (on hilly roads)

 

I use the tach instead of the speedometer for best mpg. I've found that by keeping it below 2000rpm is better for fuel economy. Faster starts are fuel killers. This goes for going up hills and passing also.

 

I use the tach instead of the speedometer for best mpg. I've found that by keeping it below 2000rpm is better for fuel economy. Faster starts are fuel killers. This goes for going up hills and passing also.

I forget, what speed is at 2,000rpm?

 

It's around 115 km/h, so 70ish mph.

 

that sounds about right. I usually get passed by everyone so its probably close to the speed limit.

 

that sounds about right. I usually get passed by everyone so its probably close to the speed limit.

Well, I guess it doesnt matter whether you are using the tach or the speedo, its saying the same thing in 6th gear. Depending on final drive gear ratios, most car manufactures say that for best mileage keep it at 65 or under.

 

I tried changing my driving habits to get every single bit of mileage out of my car when I first got it, then I remembered that I love driving, and driving like a miser isn't fun.

Besides, even now using winter gas and driving like I always have I still get around 800km out of a tank, and that's just peachy with me since our other car is lucky to get 450km out of a tank in the winter time.

 

My drive to work is mostly highway cruising at 80MPH and I regularly average 32-33MPG. I drove down to a friends house in a rural part of Florida on back roads cruising at 55mph and by the time I arrived at his house I was averaging 48MPG which was awesome (I filled up right before I left and it is about a 110 mile trip).

 

And you really trust the car's mileage computer? 48 mpg is quite far-fetched, even on a non-turbo.

 

I would guess the best speed for MPG would be somewhere around the slowest speed the car will shift into 6th gear, this would allow you the highest forward speed with the lowest engine RPM's and reduced wind drag. I would guess somewhere in the the low 50 MPH range.

 

I would guess the best speed for MPG would be somewhere around the slowest speed the car will shift into 6th gear, this would allow you the highest forward speed with the lowest engine RPM's and reduced wind drag. I would guess somewhere in the the low 50 MPH range.

That might be, but 50mph here in SoCal on our freeways is a death wish!

 

Going by my ScanGage II, I appear to get about 38-39 mpg at about 62 mph. The gage is calibrated for speed, distance, and fuel consumption, so I trust it. At 70 mph it's closer to 34-35. At 80 mph it's 29-31. These are very long term averages, over about 30,000 miles. I have seen 43.x mpg before on a one-way trip with a strong tail wind and perfect traffic conditions. Mileage improves when several cars are lined up going the same speed. Summer gas hurts by about 1-2 mpg. Rain / wet roads hurts by about 1. My old 2.2L Accord gets @ 38 mpg at a steady 55 mph, my V6 Optima can get 28-29 at about 58-59.

 

My wife has found that the computer reads VERY HI Mpg average right after you fill up the gas tank. Hers always ends up averaging around 36.5 mpg (on the display), but the first 150 miles the computer display always reads over 40 MPG. In the end, she usually fills up with gas when gauge is around the 1/4 mark and its always averaged about 36-36.5 mpg. I have no clue why it "thinks" it averages 40 mpg when the gas tank is full. She drives the same exact roads to work everyday and fills up at various different locations.

They now are selling "winter blended gas" in the northern states, and it chopped off 3-4 MPG on my wifes Sonata. It always happens in winter, and I fricken hate it.

 

Highway seems ok, but overall I am around 25mpg. This 35-42 that I am seeing here is a bit ridiculous.

 

55mph is usually the sweet spot with most cars. But modern cars should be able to get the EPA estimated at the typical speed limit of 75mph in ideal conditions. (Flat ground, no wind, etc...)

 

I'm doing a combined of 29 MPG in SoCal with a combined 65 MPH highway and some very hilly side roads. (2012 Sonata SE 2.4L)

I am consciously trying to drive "efficiently", but not getting crazy. On the highway alone I can easily exceed the 35 MPG rated mileage.

 

If you guys are running gas that is blended with Ethanol, you will never see the 35+ Mpg. I ran ours on a trip from WI to South Carolina and found out that 10% Ethanol cuts the mpg alot. I'm pretty sure we saw 4-5 Mpg reduction by running the 10% Ethanol. I buy Shell V-Power Premium only as thats the only local fuel that is Ethanol FREE. That delivers 36 mpg all summer with ac on on mostly highway driving.

 

If you guys are running gas that is blended with Ethanol, you will never see the 35+ Mpg. I ran ours on a trip from WI to South Carolina and found out that 10% Ethanol cuts the mpg alot. I'm pretty sure we saw 4-5 Mpg reduction by running the 10% Ethanol. I buy Shell V-Power Premium only as thats the only local fuel that is Ethanol FREE. That delivers 36 mpg all summer with ac on on mostly highway driving.

Keeping in mind that premium unleaded is usually at least $0.20/gal more expensive than regular, I wondered whether or not it would payoff on the better gas mileage. If your numbers are correct, then it definitely does!

The question I have then is, how do you know for sure that the Shell Premium is ethanol free? I haven't run down to the local Shell to check it out, but I thought all pumps were now labeled "May contain up to 10% ethanol".

If I could get ethanol-free gas and guarantee the same MPG improvement you're claiming than I'd be all over that!! BTW... does that difference hold true in city driving too, or just highway?

P.S. I know this is a pretty old thread, so I understand if no response.

 

I live in Bronx, NY. I GET 13 MPG on average (2011 SE - production 4/2010) .I spoke to other sonata onwers and they get +25mpg.

In a trip to florida in July i was avering 450mpg between full thanks.

 

I'm driving from NW Bama to NE Florida. So far I've driven 421 miles. Distance to empty says 173 miles. Fuel gauge is one bar below half a tank. I've been driving 8-9mph over the limit for most of the trip. MPG gauge says 35.8 MPG.

 

Eastern USA Road Trip Results

We just finished a trek of the east coast (USA). 2011 Sonata LTD, otherwise stock!. Left NJ on 12/22, and returned late on 2/14. Total of 5045 miles. At no time did any moss grow under my wheels, but my MPG was around 30-32 on the highway. I'm talking cruising at 78 MPH. In some cases, if traffic/weather/etc permitted, I was in a Conga Line at triple digit speed. Obviously, in traffic or local streets, only got slightly over 20...but that was expected.

Route south included lots of flat land, but return trip was up the Appalachian & Blue Ridge mountains, so RPMs had to vary. Took I-95 south to I-4 into Orlando, where we spent 10 days in local low-speed traffic. Drove the Florida Turnpike to Delray Beach, where we spent a month driving in slow senior citizen traffic (Palm Beach & Broward Counties). Took a 2 day side trip to Key West; on the return stopped in South Beach & Lincoln Road. Left SE Florida and returned via FL Pike back to Orlando for another week. Drove up to Birmingham, AL via I-75, I-10, I-65 and local US highways. Finally took I-59, I-24, I-75, I-81, I-78, winding up on I-287 to head home.

The last 2 days of driving was thru the mountains. Between slower traffic and the hills, I expected my MPG to drop significantly. It still stayed in the just under 30. As has been mentioned before, avoid the rabbit starts, use cruise when possible, and don't switch lanes excessively, and your mileage will stay relatively high. I don't mind +/- 30 MPG, as my prior car only got ~25 on high test.

BTW- Since we were traveling for 8 weeks, there was not a bit of room to even put an extra water bottle. Between clothes, gifts, our grandson's extra stuff, the Sonata was loaded. It still handled perfectly. In fact, on the entire trip, my wife drove exactly 0 miles and I didn't mind the driving!

 

my usual gas is from quiktrip here...and it contains up to 10% ethanal. they claim to be a top tier fuel retailer. 85% of my 30K miles have been with quiktrip gas. average about 29-31 mpg. on a whim, i went down the road and have used 100% pure gas in a few tanks to see if the mileage really improved that much. basically, the same commute and weekly routine...to/from work (56 miles), volleyball practices, soccer practices and once a week trip to lawrence, ks. (130 mile round trip). average with the pure gas was 32...an increase!! however...the pure gas was $0.49/gal HIGHER than the ethanol blend. not sure what the benefit is...at least around here.

 

My best results:

Omaha to St. Louis-427 Miles
Average Speed: 71mph
MPG: 36
Stops:0
Fuel left in tank: 1/8 (distance to empty-122 miles)

This was my "best case" study. No wife in the car to force a restroom break, St. Louis is pretty much a "downhill" drive in terms of elevation, and I-70 is pretty straight. It's no I-80 across Iowa, but it's comparable.