First long trip since we pickep up the car in July of 06. We went from central Florida to Iowa then to Texas and back to Florida in 10 days.

Ran pretty much the posted speed limits with about 38# of air in the tires we achieved the following:

Mileage from Florida to Iowa 42+
Mileage from Iowa to Texas 36.7 (30 miles per hour headwind and rain)
Mileage from Texas to Florida 42+

Found out two interesting facts:

Bottled water stored in the console with passenger temp set at 65 and rear vents open keeps the water nice and cool.

Also when we were traveling on an old 4 lane highway with the kind of pavement that creates tire noise we came to a part where the left lane had new pavement. I swited lanes and besides being quiet again I noticed the instant fuel indicator increase by 3-4 mpg. I thought this was a fluke until I switched back to the right lane with the old pavement and the mileage went right back down. Apparently the old pavement creates quite a bit of roll resistance.

On the leg of the trip from San Antonio, Texas heading back to Florida we left with a full tank and the low fuel light came on at Gulfport Ms. 588 miles. Not bad. Only made 6 fuel stops the whole 3700 trip and left with less than half a tank.

I did note one thing when getting fuel in Iowa. They are apparently really big on pushing Ethanol there since it is corn country. Mid grade with Ethanol is less than regular without. Also, they do not disclose the amount of ethanol. Here in Florida they are required to post the amount (less than 10%) which I try to avoid

I've noticed that the left lane is ALWAYS better than the right lane. Trucks travel in the right lane, so it roughens very quickly.

I travel in the left lane with my eye on the rear view mirror, so I can switch immediately. I do about 68-70 mph, and that is usually 2-3 mph less than the average driver on a 70 mph highway.

We got 21.3 mpg over 3000 hy - 70 mph on CC miles in the ancient 1998 2wd Suburban(202,400 miles). Not too bad considering the vehicle size, age, miles.

Charlie

TWENTY-one.three MPG!?!?! I hope that's a typo. I'd have to have my '04 Maxima @ 100mph to get that low mileage.

Please tell me it's at least THIRTY-one.three, especially if you're referring to the Prius in your sig.

21.3??? may as well be driving a wee 6 cammie!!!!

TCH-43mpg
VW TDI--48
08 LS 600 HL-20
08 LX 470-16

21.3 in a Prius- I would have had to drive uphill all 3000 miles to get 21.3.

No it was in our ancient Suburban, a vehicle not known to be FE. 21.3 is fairly decent at 70 mph in a Suburban. The Prius would get about 45 mpg at 70 mph with a rear hitch carrier. The Prius was too small for the long trip- 2 adults, big dog, MTB, 2 ice small chests, big futon mattress because we sleep in the back of it at rest stops- no motels.

21.3 in a Prius- if I had managed that I would sure keep that quiet!

Thanks,
Charlie

They said it was in a Suburban. That's pretty good for that vehicle I'd say.

This reference to rolling resistance seems to backup what you observed.

Quote:

Rolling resistance is primarily caused by tire deformation as the tire contacts the road surface. This has a braking affect on the car since additional energy is required to overcome the deformation resistance - therefore, the higher the rolling resistance, the higher the fuel consumption. Up to approximately 60 mph, rolling resistance has a greater effect on fuel consumption than aerodynamic drag.

Especially considering that I can barely crack 18 MPG in my wife's 2007 Denali XL (CC@70MPH) and that vehicle has a 6-spd, not 4-spd like the 98 'burb'.

doasc,
Just 18 mpg-does the Denali have the 6.0( or is it a 6.2?) or the 5.3 V-8. If you are a 1/2 ton with the 5.3 and just get 18, I'm a little surprised. If it is the 6.0( 6.2), or 4x4 or AWD, or any of the above then 18 mpg is about right.

I'm fairly sure the 6 speed only comes with the 6.0 or is it a 6.2 V-8 and that is a powerful, but thirsty motor. You might have cylinder shutdown ??

GM/Chevy have tuned the 5.3 very well for mpg and HP. It beats the 4.8 mpg wise, and it usually ties the 4.3 V-6 in respect to mpg in most platforms- vans and pickups.

The 2007 and later Suburban/Yukon with the 5.3 2wd 1/2 ton is rated
14/20. With the big motor- 6 liter I think - it is rated 12/17 a HUGE drop. I have some vague memory of the Denali or maybe the Escalade getting a really HP 6.2 liter all aluminum motor with close to 400 HP?

The old 5.7 (350) that I have really surprised me. I bought it 1 year ago with 195,000 miles. This was the first hy trip, and I never drive over 60 mph in the city,so I expected 17-18 mpg. In the city in short city interstate runs my scan gauge would show 5.3 miles per liter(20 mpg) on these short-4 mile- runs. These runs did go over 4 overpasses, but 20 mpg at 60 mph seemed about right. I expected about 17 mpg at the 70 mph we drove. The 21.3 mpg was a very pleasant and HUGE surprise. It is EPA rated- current ratings - at 12/17 . These are real numbers over 3021 miles - 142 gallons - not scan gauge numbers.

I don't have a good explanation. It was roundtrip,so it wasn't because of altitude drop or wind direction. The altitude does help- Flagstaff is 7000 feet NOLA is sea level- so we probably averaged 2000+ feet over the trip with less aero drag. I did use 43 psi tire pressure and the tires are worn; both helped. The Mobil I 5W30 didn't hurt. We used the cruise control all the time- that helps. It has the little tires/wheels 235/75 15 not the big 265/70 16 on current ones (I suspect the Denali might have even wider tires-that doesn't help).The high miles 202,400 on the motor probably helped. It usually doesn't but in this case it probably did. Every surface is polished in now. It used about 24 ounces of oil over the 3021 miles, so it is using a little oil, but not bad for the age/miles.

Sorry to horn in on the thread, but long trip mpg and ways to improve it interest me. I think you -gandyfire - are onto something with the left lane having lower RR. I used it for the ride comfort; the better mpg didn't occur to me. I was in the left lane 95% of the distance-this helped.

Thanks for the tip gandyfire,
Charlie

Yep, you pretty much called it. The Denali has a 6.2 slightly detuned from the Esclade's 400-hp. AWD with big 275 tires on 20s. No engine management (4-6-8) but it does have a DVD player

In 2006 we rented a Suburban in Las Vegas to tour the Grand Canyon. Drove over 1000 miles but we averaged around 17-18 MPG. However, much of that driving was at elevation and it was constantly shifting out of overdrive with any increase in grade.

It was good to see Gandyfire observing 36.7-42+ MPG across his 3700 mile trip. Especially without employing any HM techniques. This sites database averages on a per car basis, so there are many one-off reports that can be substantially lower or higher than the average. Averaging a 3700 mile trip provides a much more accurate average for my purposes.

doasc,
Maybe the detuning is strictly "paper" detuning to make sure Escalade buyers are getting more power - on paper - than Yukon buyers. Not like would ever know the vehicles made the same power.I guess it is more likely that GM just dialed slightly different tuning in the engine control module; let the Escalade rev a bit higher.

Either way a very nice motor. I bet it is actually very efficient. If GM could have read the future they would have geared it a bit taller. A powerhouse motor like that could easily cruise at 1400 RPMs at 60 mph instead of the 1550-1600 RPMs it probably turns.

I'm going on the same long trip in 3 weeks. I might slow down to 68 mph. If the Suburban had a lower mile motor(202,500 miles), I would switch to 0W30 Mobil I instead of 5w30.

Gandyfire, I'm sure you're onto something with the left lane smoothness. I'll be in it 99% of the time.

Thanks,
Charlie