Hey friends. I'm curious if any of you can support/back up the experience I'm having with my 2005 Chevrolet Suburban C1500 LS. Three months back we purchased it, details are: bone stock front to back, 5.3 V8, 2wd, 117K miles.

Our first month (June) we filled up at the beginning of the month, and used the vehicle normally. Lots of trips around town, one trip towing the quad on the trailer slowly up dirt roads, accessing hiking trails, one or two freeway slogs, and averaged 17.69 mpg overall when we filled up in July 1st. The trip computer claimed 18.1 mpg average for June. I do my MPGs manually as well.

Middle of July (this month) we put on four brand new Michelin LTX MS2 tires, size 245/75 R16. $816 well spent. The ride is quiet and very smooth. However, we did ALL around town driving, shooting trips up the canyon, etc. And there were several days I drove into work and did some full-throttle driving because I was in a hurry and enjoying the power. Today I filled up and we averaged 15.56 mpgs in July.

TODAY: I took my boys up to Rocky Mountain Raceway for the drags. We filled up at Maverick on our way out to the Freeway (mentioned above). I filled the tank clear to the top (yes, I topped it off till I couldn't get any more in) with 89 octane fuel, reset the MPG computer, and TRIP A odometer. Then I drove as carefully as possible without annoying other commuters out to I-15 and up to Rocky Mountain Raceway. My goal was to see how good of freeway mileage I could get. As soon as I hit the freeway I set the cruise at 60mph (65mph speed limit), turn ON the A/C, some music, and me and my boys cruised up the highway. I had a light breeze to my back, and the AVERAGE MPG computer up on the dash. I watched up bump up gradually till it leveled at 29+mpg!!! Never hit 30. Level freeway.

Went to the drags, headed home. Did the same thing, cruise at 60mph, A/C ON, music on, me and my two boys in the truck. On the way home, cruising into the breeze head on, the computer bumped down and was telling me 25.7-25.9mpg most of the way. This seemed too good to be true, so when I got back to Springville and exited the freeway I immediately turned into a Maverick and filled up. Again, I topped it off as far as I dared without spilling on the ground. It took 4.03 gallons. TRIP A said we'd driven 111.3 miles round trip - and I just verified that with Mapquest which read 107.88 miles round trip, except I took a several mile detour (got lost) on the way there.

YOU DO THE MATH! I drove 111.3 miles on 4.03 gallons of fuel. I'm not lying here, I'm just curious if anybody else has had such incredible fuel economy with their C1500 Suburban. I expect to beat 20mpg, not 27mpg! But the vehicle computer and my own manual calculations say it's true. 91% freeway driving.

Even if I'd gotten 18mpg we love our new Suburban.

Chris

 

Welcome to the forum.

Sounds like Chevy let one slip thru.

There's a definite correlation 'tween mpg and speed. Mine runs about 18 @ 70 and 19-20 @ 65. Manual calculations. The DIC runs about 1 mpg higher. Also w/o the extra 200 lbs of 4WD hardware and added friction doesn't hurt on yours.

Would strongly advise against topping off as it will damage the evaporative emissions system. Just stop at the first click off to be safe.

 

Thanks 73shark. I'll do as you suggest with regards to topping it off. I suppose over time it would average out correctly anyway if that's how I always did it. I'm assuming folks will read my post and blow it off. That's ok, I'll keep enjoying my Suburban! I just figure I can't be the only one. I'm having a competition with my neighbor who just bought an 07 Mercury minivan to see who gets best MPGs. His last tank they averaged 14.7mpg.

 

My best was 23mpg for about an 80 mile round trip on flat road, 55mph in my 07 Tahoe..its possible under ideal conditions to get a higher then rated MPG but its the "ideal" conditions that don't happen often...

 

If you fill up at the same station and pump, the first click will be fairly consistent.

Best I ever got in my '07 was 22 mpg on a 150 mi trip back from the lake when I forgot to take it out of 4WD from pulling up and out of a steep gravel driveway. Go figure.

 

I've owned it longer now, and it's still the same story. Tonight we drove from Springville to Centerville and back. 27.5 mpg average. 60 mph freeway, (right lane) a/c on half of the time, whole family and stuff loaded up. I'm very pleased with this mileage.

 

niiice. enjoy it while you can. that kind of mpg is unheard of typically.

I dont think even the diesel conversions get that good of mileage... :dunno:

with mileage that good I wonder what it would pull at 65...

I think the best my suburban (5.3) did was 17-18ish, but I typically had my foot in it so it settled in the 15-16 range while we had it. got it with 147k and was gone by 160k,

my pickup (5.7) tho, the best it ever got on a trip was 18. It's currently down in the 13-15 range now with over 200k

 

Over the past 7 months I've tested it at different speeds, and it's boringly consistent.
60 mph = 26 + mpg
65 mph = 25 + mpg
70 mph = 23 + mpg
75 mph = 21 + mpg

I've run the 124 mile round trip from here to Centerville and back and those different speeds to test it, and that's what I see every time. We typically do this trip 2-3 times per month so I've had lots of opportunities to test it. I also tested it on our Thanksgiving trip from here (Utah county), through Las Vegas down to Phoenix (11 hours). The whole family loaded up, A/C on the whole time, all of our stuff on board, 70-75 mph with cruise control used, plus stops along the way = 21 mpg average on trip.

 

Curious as to what your DIC says for average.

 

Back in 2008 we took a trip to Colorado in our 2005 Suburban. We were running around one day and before we headed back to our hotel in Denver I filled the tank, we were in Woodland Park Colorado, we drove through Colorado Springs and then into Denver. I notice the DIC was showing 28-29 mpg. I did not believe the DIC so as soon as we got back I topped off (I always stop at the first click) the tank, and on an 88.7 mile trip we used 3.16 gallons of gas. There were a few other times we got 26-28 mpgs in Arizona and New Mexico but as soon as we would get back into Texas the MPGs would drop to our average 18-19 mpgs. don't know if it is altitude or just better fuel with less ethanol or what, but it does happen.