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is it ok to run 87 octane gas in an 8.1 or should it be 93+?
 

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If it's stock, 87 will be fine. If you have it tuned for something else it may ping. It may not run as good either.

Mine is tuned for 93 and I ran a tank of 87 through it just to see the difference. It didn't ping, mileage wasn't as good but the truck seemed to run ok. It seemed a little sluggish but nothing anyone else would have noticed.

Bill
 

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Intersting......I just bought an '04 Sierra EC/SB 8.1/Alli 3.73 (stock)

Pulled an enclosed M/C trailer (12" extra height) to Florida and back.....about 6000# gross tralier weight......3400 mile average was 9.7......I commute 180 miles a day and I have been "playing to see where the mileage would be.....running exact route daily with 87 octane....10.5 to 11.6......using 92/93 octane, it went to 12.7 to 13.1........
 

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Intersting......I just bought an '04 Sierra EC/SB 8.1/Alli 3.73 (stock)

Pulled an enclosed M/C trailer (12" extra height) to Florida and back.....about 6000# gross tralier weight......3400 mile average was 9.7......I commute 180 miles a day and I have been "playing to see where the mileage would be.....running exact route daily with 87 octane....10.5 to 11.6......using 92/93 octane, it went to 12.7 to 13.1........
You picked up 3 mpg by switching to 93 octane?..:eek: Better check that calculator, I find that hard to believe. I sure don't wanna start an octane war thread, but if your rig is tuned for 87 octane and is in good working order, it won't run better on 93. Now to add the caveat...unless there is something wrong with your motor, i.e. carbon build up, bad tune, excessive heat, then higher octane might help. Also, if you added a tuner then you may need to run 93 octane.
JP
 

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I used to run 93 or 94 until gas prices went ape ****. Now I run all 87 and I can't tell the difference. I have a Hypertech tuner on the '01 tuned to 87 and no pings.
 

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Well,

I still run the same route every day (have for 9 years) and my mileage last night for the round trip was 13.1........best I got on 87 was 11.1.....so that is 2 mpg, not 3........I have checked to seeif anything had been changed on the truck and to the best of my knowledge no upgrades have been done. BTW, those mileages on on a calculator not the truck computer........(whic is very close)

But then I was told I would never see above 8 pulling my trailer either......
Everything else seems to fall into line on this motor.....1 qt every 3M miles, etc, etc.........

Tim
 

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Well,

I still run the same route every day (have for 9 years) and my mileage last night for the round trip was 13.1........best I got on 87 was 11.1.....so that is 2 mpg, not 3........I have checked to seeif anything had been changed on the truck and to the best of my knowledge no upgrades have been done. BTW, those mileages on on a calculator not the truck computer........(whic is very close)

But then I was told I would never see above 8 pulling my trailer either......
Everything else seems to fall into line on this motor.....1 qt every 3M miles, etc, etc.........

Tim
I guess stranger things have happened, but it's tough pickin' up that much mileage even when you add mods to it, i.e. some tuners boast mileage increases, and your truck is using a 1 qt of oil every 3000 miles. :eek:

This boggles my mind. I may have to run a tank of 93 through my 6.0L just for giggles and see what happens.
JP
 

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Also been running 87 since new - no problems in 57,000 miles and I tow 10,000 lbs at least one weekend a month.
 

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HB,

Well you're probably right.............after the truck settled down I'm getting about the same on the highway with either 87 or 92......13 to 14 and 10 in town. About 9.5 with the M/C trailer.

Happy with the power of the 8.1 but would like to pick up a bit of mileage when not towing......any suggestions outside of headers and pipes (they're on the way).
 

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HB,

Well you're probably right.............after the truck settled down I'm getting about the same on the highway with either 87 or 92......13 to 14 and 10 in town. About 9.5 with the M/C trailer.

Happy with the power of the 8.1 but would like to pick up a bit of mileage when not towing......any suggestions outside of headers and pipes (they're on the way).
I have the 6.0, but some 8.1 owners say they can pick up 1-1.5 mpg with a good tune on the PCM. Maybe some of them will chime in. Only other thing might be a set of taller tires, but it'll be a minimal mileage increase. 235/85/16's at about 70psi will pickup a tad bit of mileage, but most don't like the small tread width. They are about .3" narrower than the 245's and the same height as a 265/75/16. Make sure all extra weight is out of the rig and a conservative driving style will do more than anything else, mileage-wise.
JP
On Edit: You also could switch all fluids to synthetic, i.e. engine & tranny oil, front & rear diff oil. Use a good syn like Red Line, Amsoil, Mobil 1 etc. This might be good for a little extra mpg.
 

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Dual Fuel

The 8.1 is a so-called dual-fuel motor. It will run on either high or low octane gas. Buuuuuut, if you are doing heavy towing in steep terrain, the computer will respond to knocking by retarding the timing sooner than with high octane. That will then require a lower gear. In my 8.1, 3500 ex. cab. 4X4, towing a heavy 5er, I can readily see the difference. The high octane permits me to use 4th gear @ 4000+ rpm (which Chevy says is fine, and it is very smooth) on a steep pull and usually maintain 60 mph or so (with the ZF 6 speed manual and 4.10 gears). Also, on largely level terrain, the high octane will allow me to stay in 6th gear overdrive and maintain freeway speed more easily. Lower octane requires dropping down to 5th gear more often. As a big bock fan for decades, I like the 8.1 a lot — but it needed another 100 lb. ft. to be perfect.
 

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Higher octane gas burns slower than the cheap stuff. It may create a bit more carbon build up in those engines not needing it, but not enough to worry bout.
I've run the cheapest stuff I can find for 60K miles now and no problems..... yet
 
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