What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[George B]

We have Exxon and Mobil down here, I get the same on my 15, idle is more noticeable and weird drop in rpm some times. A tank of chevron and its better. The work around for me was some Techron fuel system cleaner, makes it alot better. I would throw a good fuel system cleaner and some chevron if you have it and give it an Italian tune up.

The reason I think is somewhat mechanical with how the cylinder head design is and the other is the fuel mapping. You could probably push through the fuel mapping with about 5 tanks of gas from there and solve some of the issues, but its a gamble for sure.

Probably a 1-2 mpg loss also noted with the switch?

I can't say I noted the mileage but my driving is so mixed I can't get repetitive data. I typically run on the 88 stuff or E85 from kwik Trip here in Wisconsin. I Ran two tanks of 0% ethanol 91 from Kwik Trip to see how it would do and verify my fuel alcohol content calculation. My third tank was Mobil 91 0% ethanol and the truck runs poorly on it. I noted that with their 89 10% blend too.

 

[Bigkevschopshop]

I can't say I noted the mileage but my driving is so mixed I can't get repetitive data. I typically run on the 88 stuff or E85 from kwik Trip here in Wisconsin. I Ran two tanks of 0% ethanol 91 from Kwik Trip to see how it would do and verify my fuel alcohol content calculation. My third tank was Mobil 91 0% ethanol and the truck runs poorly on it. I noted that with their 89 10% blend too.

Try going back to QT and should be back to fine... For some reason the blends on Mobil and Exxon are just not great for these motors...Run a good cleaner through it and some Chevron or QT fuel and she should be happy again.

 

[swathdiver]

I can't say I noted the mileage but my driving is so mixed I can't get repetitive data.

You can by calculating for gallons per hour or miles per gallon using city versus highway percentages.

We carry so much fuel that for me it is hard to run the tank empty doing just one thing, would take over 7 hours of driving at highway speeds.

For example, my wife and I just came back from a long weekend on Daytona Beach. I filled up the truck two days before we left and we used it to take our grandson to summer camp (learning about horses) and back. Then we went to Daytona, drove through torrential rain which kills gas mileage, drove on the beach for 10 miles or so in 4x4 and then came home, driving in torrential rains again for about an hour. She burned 25.3 gallons of Love's Travel Stop gas (I'm testing for upcoming trip) over 406 miles over 10.8 hours of run time.

The average speed works out to 37.6 MPH and that works out to 40% City and 60% Highway driving. She burned an average of 2.3 gallons per hour. Pretty consistent for a 40/60 tank of gas. The mpgs fluctuate more but the GPH is more stable.



There were lots of stretches of soft sand on the beach that could not be avoided. A 1-ton Ram got stuck in front of me. The Michelin Defenders pleasantly surprised us by getting through it easily and the treads did not fill up with wet sand, they kept clean like the KO2s.

 

[Doubeleive]

Ordered the dorman drive shaft off of amazon $314 delivered and I have a 30 day return period.

drive shaft should be here in 3-5 days if it doesn't work well I will have one made for higher speed rotation

 

[Fubar0715]

You can by calculating for gallons per hour or miles per gallon using city versus highway percentages.

We carry so much fuel that for me it is hard to run the tank empty doing just one thing, would take over 7 hours of driving at highway speeds.

For example, my wife and I just came back from a long weekend on Daytona Beach. I filled up the truck two days before we left and we used it to take our grandson to summer camp (learning about horses) and back. Then we went to Daytona, drove through torrential rain which kills gas mileage, drove on the beach for 10 miles or so in 4x4 and then came home, driving in torrential rains again for about an hour. She burned 25.3 gallons of Love's Travel Stop gas (I'm testing for upcoming trip) over 406 miles over 10.8 hours of run time.

The average speed works out to 37.6 MPH and that works out to 40% City and 60% Highway driving. She burned an average of 2.3 gallons per hour. Pretty consistent for a 40/60 tank of gas. The mpgs fluctuate more but the GPH is more stable.

View attachment 404235

There were lots of stretches of soft sand on the beach that could not be avoided. A 1-ton Ram got stuck in front of me. The Michelin Defenders pleasantly surprised us by getting through it easily and the treads did not fill up with wet sand, they kept clean like the KO2s.

Everyone has to appreciates the time and effort @swathdiver that goes into these scientific journals. Personally, always in awe of how well the details are explained and backed with real world data...You sir, could never work for the news media-to many facts!!! Good job!

 

[wjburken]

Two times now I have fueled with Mobil fuel and noticed my Burb doesn’t run as well. It develops a hesitation getting back on the throttle after coasting. It goes away with a change in fuel. So I put in 18 gallons of E85. To burn on for a few days. Wonder why it does that.

I thought it was law that folks in Wisconsin had to get gas at Kwik Star/Kwik Trip.

 

[George B]

I thought it was law that folks in Wisconsin had to get gas at Kwik Star/Kwik Trip.

Almost is. It goes to the Senate this fall.

 

[j91z28d1]

You can by calculating for gallons per hour or miles per gallon using city versus highway percentages.

We carry so much fuel that for me it is hard to run the tank empty doing just one thing, would take over 7 hours of driving at highway speeds.

For example, my wife and I just came back from a long weekend on Daytona Beach. I filled up the truck two days before we left and we used it to take our grandson to summer camp (learning about horses) and back. Then we went to Daytona, drove through torrential rain which kills gas mileage, drove on the beach for 10 miles or so in 4x4 and then came home, driving in torrential rains again for about an hour. She burned 25.3 gallons of Love's Travel Stop gas (I'm testing for upcoming trip) over 406 miles over 10.8 hours of run time.

The average speed works out to 37.6 MPH and that works out to 40% City and 60% Highway driving. She burned an average of 2.3 gallons per hour. Pretty consistent for a 40/60 tank of gas. The mpgs fluctuate more but the GPH is more stable.

View attachment 404235

There were lots of stretches of soft sand on the beach that could not be avoided. A 1-ton Ram got stuck in front of me. The Michelin Defenders pleasantly surprised us by getting through it easily and the treads did not fill up with wet sand, they kept clean like the KO2s.

you ever try Murphy's or whatever the Walmart fuel is? only time i ever really noticed one fuel running better than another was 02 ls1 z28. heading north out of Tampa, there was a Walmart around Bushnell. I'd stop there and fill up and my car always felt smoother on that one tank and then back to normal. it was weird, but is did it consistently.

always wondered if it was just me.

 

[swathdiver]

...noticed one fuel running better than another

All the time for 30+ years. Engine idles smoothest and gets its best mileage on Chevron's 93 compared with all the others. Running E85 is even better, it's like cheap race gas.

I tend not to use additives to the gas tank but have run those little Walmart bottles of fuel injector and system cleaner before I discovered Ethanol. Also ran some octane booster when running a hotter tune at the drag strip on gasoline, it was Lucas.

We tend to run E85 when the truck will be local and don't have any long trips planned and 93 from mostly Chevron when we need the truck ready to make 400+ mile runs.

 

[j91z28d1]

interesting.. used to have a chevron card for years but their gas was always expensive and I never noticed it being any better than anything else so we ditched the card at some point. only gas I ever really noticed was that one station and that car. it was a manaual tranny so you could feel everything thru the shifter.

this yukon isn't rated for e85 or I'd run it, since there's a station near by. weird because you think a hybrid would and I doubt anything in the fuel system is different than the normal one. must be a tuning issue, since it uses it own ecm. but it also doesn't require 93 either thou, it runs fine on everything. I towed on 87 getting 13mpg lol.

it also doesn't idle when stopped so it's hard to feel idle roughness and since the cam in these has like no off idle tq. the tranny let's it have rpm anytime under a load so it doesn't lug around low rpm where it needs good fuel either.

always been interested in mpg