Avg 19.0 mpg Hwy-6.2L

donjetman

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2007 Yukon Denali w/all aluminum 6.2L (L92) w/180,435 miles

I'm averaging 19 mpg on the "hwy" now (driving the speed limits-80 to 55)) between our TX and CO homes which are 967 miles apart. I've done that leg 4 times this summer averaging 18.4, 19.3, 18.7, and 19.7 mpg each time. There was almost no wind on all 4 legs. Gas mileage improved slightly (18.8 vs 19.2) on my Aug trip vs the July trip. I may have used the ac a little less on the Aug trip. That would acct for the improvement.

Since its last oil and filter change 5 mths ago, I have put 6235 miles on this load (11 qt sump) of 0w20 oil (Amsoil) and the dipstick indicates it's used about 1/2 qt. I drained the catch can and only 1.25 oz came out (a good thing).

Avg moving mph on July trip = 65.7 mph
Avg miles per gal on July trip = "18.8 mpg"
Total fuel used July trip = 102.4 gal premium

Avg moving mph on Aug trip = 65.7 mph
Avg miles per gal on Aug trip = "19.2 mpg"
Total fuel used Aug trip = 100.6 gal premium

I plan to send in a sample to a lab for UOA (used oil analysis).DSCN0426.JPG
DSCN0431.JPGDSCN0430.JPG
 

jdwood1111

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Nice!! And with no AFM on the 07 right? I have a 2011 with a Range device and the best i have gotten is 17.
 

RST Dana

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2007 Yukon Denali w/all aluminum 6.2L (L92) w/180,435 miles

I'm averaging 19 mpg on the "hwy" now (driving the speed limits-80 to 55)) between our TX and CO homes which are 967 miles apart. I've done that leg 4 times this summer averaging 18.4, 19.3, 18.7, and 19.7 mpg each time. There was almost no wind on all 4 legs. Gas mileage improved slightly (18.8 vs 19.2) on my Aug trip vs the July trip. I may have used the ac a little less on the Aug trip. That would acct for the improvement.

Since its last oil and filter change 5 mths ago, I have put 6235 miles on this load (11 qt sump) of 0w20 oil (Amsoil) and the dipstick indicates it's used about 1/2 qt. I drained the catch can and only 1.25 oz came out (a good thing).

Avg moving mph on July trip = 65.7 mph
Avg miles per gal on July trip = "18.8 mpg"
Total fuel used July trip = 102.4 gal premium

Avg moving mph on Aug trip = 65.7 mph
Avg miles per gal on Aug trip = "19.2 mpg"
Total fuel used Aug trip = 100.6 gal premium

I plan to send in a sample to a lab for UOA (used oil analysis).View attachment 378917
View attachment 378918View attachment 378919
Did you verify your mpg with manual calculations at the pump?
 
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donjetman

donjetman

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Yes all the math works. What the DIC says, the pump says.
 

Geotrash

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2007 Yukon Denali w/all aluminum 6.2L (L92) w/180,435 miles

I'm averaging 19 mpg on the "hwy" now (driving the speed limits-80 to 55)) between our TX and CO homes which are 967 miles apart. I've done that leg 4 times this summer averaging 18.4, 19.3, 18.7, and 19.7 mpg each time. There was almost no wind on all 4 legs. Gas mileage improved slightly (18.8 vs 19.2) on my Aug trip vs the July trip. I may have used the ac a little less on the Aug trip. That would acct for the improvement.

Since its last oil and filter change 5 mths ago, I have put 6235 miles on this load (11 qt sump) of 0w20 oil (Amsoil) and the dipstick indicates it's used about 1/2 qt. I drained the catch can and only 1.25 oz came out (a good thing).

Avg moving mph on July trip = 65.7 mph
Avg miles per gal on July trip = "18.8 mpg"
Total fuel used July trip = 102.4 gal premium

Avg moving mph on Aug trip = 65.7 mph
Avg miles per gal on Aug trip = "19.2 mpg"
Total fuel used Aug trip = 100.6 gal premium

I plan to send in a sample to a lab for UOA (used oil analysis).View attachment 378917
View attachment 378918View attachment 378919
That's about 2 mpg better than I get in my '07 XL Denali. Yesterday and the day before I drove a total of 980 mostly interstate highway miles at a steady 75 mph.

Apart from the thinner oil you're using, there are a couple of other important factors I see that might also account for some of the difference:

1/ Altitude. Thinner air means less air mass to push out of the way and less power that the engine can make. (I know you're a pilot and know this already, but for the others who may not) a normally-aspirated engine loses 3% of its power (and its ability to consume fuel) for every 1000' above sea level. Normally-aspirated piston engined aircraft burn less fuel over a given distance at higher altitude due to both of these factors, though mostly due less air mass to move.

2/ Driving style. The difference between averaging 17.5 and 15 or less on the same route is how often I floor it to pass someone or get out of someone's way. Also, dealing with heavy traffic drops my mpg significantly.

My bet is that the thinner oil is netting you some incremental gains, so thanks for raising it as a possibility.
 
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donjetman

donjetman

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That's about 2 mpg better than I get in my '07 XL Denali. Yesterday and the day before I drove a total of 980 mostly interstate highway miles at a steady 75 mph.

Apart from the thinner oil you're using, there are a couple of other important factors I see that might also account for some of the difference:

1/ Altitude. Thinner air means less air mass to push out of the way and less power that the engine can make. (I know you're a pilot and know this already, but for the others who may not) a normally-aspirated engine loses 3% of its power (and its ability to consume fuel) for every 1000' above sea level. Normally-aspirated piston engined aircraft burn less fuel over a given distance at higher altitude due to both of these factors, though mostly due less air mass to move.

2/ Driving style. The difference between averaging 17.5 and 15 or less on the same route is how often I floor it to pass someone or get out of someone's way. Also, dealing with heavy traffic drops my mpg significantly.

My bet is that the thinner oil is netting you some incremental gains, so thanks for raising it as a possibility.
Your point #1 I know all too well from being a pilot since 1977. I often use our motorhome to tow our 07 Toyota FJ Cruiser to our CO mtn home where we use it locally. We never driven the FJ on any long trips, so I can't tell you what it gets for gas mileage on the hwy in TX or CO. Its local gas mileage improves from 20 in TX to 23 in CO.

#2 There is no traffic ever on our route. Most all the hwys are 4 lane, or have a passing lane every few miles, so no need to stomp it too pass, or in my case be passed.

Where we get the worse gas mileage on this trip is in the first 150 miles and last 150 miles, near our TX home. The area is called the TX Hill Country. Speed limits are high, 75 & 80 mph, and its HILLY. Altitude may vary between 1000'asl and 2000' asl. This combination kills mileage. The rest of the TX trip (2/3rds) is fairly flat and open, and the speed limit is 75. In NM its 70, and in CO it varies between 55-& 75. There's one mtn pass = Raton Pass. Isn't a big deal. Elevation is about 6,500'asl on both sides and the tops out at about 8,000'asl.

If the wind gets to blowing it can hurt or help mileage a lot. Also, we drive the Denali there and back in the winter where the temps can reach -20*f. The 0w-20 will come in handy then.
 
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B-train

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I just ran a route from WI to NM, CO, and back to WI in my 2008 Denali. I have more aggressive tires for offroad driving (factory size though, 18 in) a rooftop tent (with a home made air deflector which is pretty sweet!! And helpful). My numbers range quite a bit depending on wind. If it's no wind, or very light, I can get between 17 - 18.5. If driving into the wind, it's about 15.5 - 16.8.

Without offroad gear on, factory 20 inch wheels with road tread, the mpgs have been as high as 21 in the mountains and about 17.5-19.5 on flatland depending on wind.

I find that 75 to 77 seems to be the sweet spot for the motor. Between 1800 and 2100 a programming/fueling change takes place in the mapping and it really likes to pull.

Another fun thing to try is to use a code scanner that provides real time data and watch the spark advance and fuel trims. That, coupled with a reset mpg meter can show you how best to control the right foot and be in tune with your ride
 

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