2016 Sierra Z71

Pythonman · December 9, 2016

Picked up my first GMC pickup a few weeks ago. She's got the 5.3l engine and six speed transmission with 3.42 gearing. After four Ford trucks I have to say, "why'd I wait so long?" The GMC shifts smooth, rides very nice and runs very quietly which I like. Glad I did some research on forums like this one before I bought as I had not know before what top tier gasolines were and that only GMC/Chevy trucks can come from the factory with G80 or automatic locking differentials. The mileage on this truck is very good. However, my first two fill ups were with 89 octane from a Mobil station and the last and third fillup was from a Luke's station that I've went to for years. I only went to the Mobil because I'd read it was a top tier gas station and the owners manual for the Sierra calls for that gas. But, since I hadn't ruined any of my other vehicles with Lukes I thought I'd see if there was any difference. There was indeed a difference! On the Mobil 89 I was averaging about 17mpg in town driving since, that's about all the traveling I've done so far the first 700 miles. With the Lukes 89 I've always bought I was averaging 14.5mpg and the engine rumbled and shook the cab gently at stops. I'm like Wth have I done putting that garbage into my truck? So, after running out 6 gallons over 80 miles or so I went back to the Mobil station and topped back off with 93 oct and the truck is running smooth again and so far it's getting about 19mpg. My wifes 2016 Jeep Grand Cherokee has been averaging 19mpg with lukes gas since day one and today I filled up with Mobil for the first time, 89oct and now it's averaging 23mpg! The Jeep didn't run rough with the Lukes gas but mileage sure suffered. Just thought I'd share these observations.

CadillacLuke24 · December 9, 2016

It is surprising how top tier gas can help. I always get better mileage on Sinclair gas as opposed to Loaf 'N Jug. Glad you found the sweet spot!

emeryz28 · December 9, 2016

there is a place that sells gas called.....Loaf N Jug??

slj2008 · December 9, 2016

welcome

'01LS1 · December 9, 2016

there is a place that sells gas called.....Loaf N Jug??

Ha! Had to look that one up too. Chain convenience store owned by Kroger.

https://www.facebook.com/loafnjugstores/

amxguy1970 · December 9, 2016

4 mpg? I am thinking driving, weather and many other parameters played a large roll in those numbers...

Tyler

Willyone · December 9, 2016

4 mpg? I am thinking driving, weather and many other parameters played a large roll in those numbers...

Tyler

Yepper....I agree

I seem to be down a couple or few MPG over the last month or so. I attribute it to the winter gas mix and cold weather... oxygenized gas I believe they call it. But then, I've been using the 87 octane. Might help if I went with the 89??

Pythonman · December 10, 2016

Here she is

Pythonman · December 10, 2016

4 mpg? I am thinking driving, weather and many other parameters played a large roll in those numbers...

Tyler

Well with 40 miles since topping off with six gallons of 93oct the average Im getting is 16mpg in town. And that includes some warmup time in the driveway and waiting on trains etc. Pretty good still. What I didn't notice when new from dealer and with the first two fillups with Mobil 89 was any shuddering vibrations when the engine went from V8 to V4. Soon as I filled up with crap gas and started getting bad mileage I noticed the truck seemed to be stuck for the most part in V8 mode and when it did go to V4 I'd get the shuddering momentarily. I hope once the truck runs out of the bad gas and I fill up with a full tank of the good stuff that the shuddering disappears again. So far with 740 miles or so the transmission (six speed) has shifted oh so smoothly! I like the shifts. On occasion I will hear a clunk from the rear when making a turn left or right at lower speeds but I'm attributing that to the locking differential which none of my Ford trucks ever had. Wish they did. I've driven this truck like a grandpa would have back in the 50s as I've long believed that a smooth careful break in works better in the long run and once broken in for 500 miles I start seeing what kind of power is under the hood, but only after the engine is fully warmed up. This has always rewarded me with good strong, reliable engines that don't burn oil or leak. Now having had a 2014 F150 with the 5.0 for a year and a half I can directly compare the performance of that engine to the 5.3l ecotek3 in the Sierra.

The Fords engine was peppy without much feeling of low end torque IMO. I like the coyote engine, especially the one that was in my 2013 Mustang which was rated at 420HP with premium gas. But the truck version was only rated at 365HP in the 2014 F150 supposedly so they could improve torque but they didn't. It was just dumbed down to save gas I think. Still, it had a great sound and would take off like a rocket if I wanted it too. The Sierra felt pretty mush in the gas pedal from day one but the ride and the quietness made it a joy anyhow and I wasn't in a hurry to find out if it had power or not yet as I was only 3 weeks out from a nasty head on collision on the highway. But in the last 150 miles or so I've had a couple of occasions where merging onto a busy road I'd get on it a bit and the tach would peg at about 5500rpms and the Sierra's front end would come up a bit as she sprinted to 60 every bit as good as my Ford did and with a bit better low end shove. It feels like the engine's waking up and I'm noticing that when I take off from a stop light with just a touch of pedal now she's getting up to whatever posted speeds quickly and quietly and purposefully. She's making plenty of power with lots less mush in the pedal. As long as the truck and the engine are reliable and I can count on it to get me back and forth to work for the next 8-10 years or longer I will be very happy because that's my main use for it besides getting loads of firewood home. Beyond that, I hope GMC and Chevy keep making these out of mostly steel for the frames and bodies!