91 octane

wirlybird

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Just to chime in. For my '97 5.7L Vortec Tahoe I found that the truck runs poorly and reduced MPG with 87 gas containing ethanol.
Using non ethanol 87 and it runs very good and averages 17MPG and this is with a 332,000 mile engine.
I recently tried 91 non ethanol and even though the truck "seemed" to have a little more "pep" the idle was rougher and it seemed to develop an intermittent hesitation at speed.
Switched back to 87 non ethanol and it runs great.
The truck did have a computer tune when it was new but I don't recall if it was for 87 or 91. My guess is it was for 87 since the truck was all stock.

As a side note I tried 91 non ethanol in my 97 K3500 7.4L vortec and it ran like crap. Back to 87 and it runs great.

Just my experience.
 

2drXmobb

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So 91 doesn't have ethanol and ethanol is bad? I'm not sure which gas stations doesn't have ethanol I thought they all did. I pay about 4-5 dollars a gallon for regular fuel in California. I really don't care for mpgs at this point I just pump fuel and go before I used to pay in chump change just to get a gallon . When I was younger my uncles always told me to use expensive fuel I wasn't sure if he ment octane or cheap gas stations we have mom and pop shops and what I hear is they don't use alot of detergents so they clog up your fuel filters and injectors which cause poor performance. People always said to use she'll, 76, or Chevron the more expensive brands because it had more detergents. Not sure if it's branding that sells or the quality of the fuel ⛽
 

thegawd

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top tier fuels pumps are labeled with the top tier sticker and yes they are more expensive. the ethanol content of the grades of fuel is required to be labeled as well.

top tier fuels are more highley refined fuels that may meet a higher standard than mandated.

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Erik the Awful

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The closest gas station to my house had 91 octane, no ethanol for $2.99/gallon the last time I passed. 87 was $2.79.
 

PlayingWithTBI

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I just filled up with 91 at QT today (Top Tier 10% ethanol) for $4.35 - Regular is 3.85 :mad:

LET'S GO BRANDON!
 

alpinecrick

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is there any harm in running 91 octane (top tier shell) fuel in a stock 5.7 vortec motor? I only buy ethanol free fuel for my small engines, and lately that seems to only be available in 91 octane. the small engines love it and so I put 5 gallons of it in my farm truck and it loved it. friggen tonnes of power. I understand the benefits of top tier gas and how it cleans the fuel system but is there any drawback other than the price? my burb has a 42 gallon tank, i dont think I would want to pay the premium price to fill that sucker up!

Al

https://www.shell.ca/en_ca/motorists/my-fuels/shell-v-power-nitro-plus-premium-gasoline.html
Shell premium is supposed to be the best gasoline out there. A few years ago some labs compared different brands of premium in both Europe and USA, Shell premium produced the lowest emission and kept carbon to a minimum better than any of the other brands tested.

As far as power I haven’t been able to see or tell a difference in power between mid grade vs premium in my 5.7/5.0/5.3 Vortecs. But here at altitude mid grade gets better milage and more power. We do have ethanol blend gas mandated in Colorado though.
 
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Best thing a person can do is get some kind of scanner with advanced GM PIDs and monitor knock retard. If the PCM is retarding timing on 87 there is power and mileage to be gained with higher octane.

I like a ELM 327 device and OBD Link with GM Advanced upgrade.

This Bluetooth ELM327 device and a smart phone or tablet with OBD Link with GM Advanced update has not let me down. I also use it for my 8.1 99 Tahoe, my Nissan and Inifiniti. Downloaded the Nissan/Infiniti advanced stuff too. Can look at all the modules, read and clear codes, etc. This will let you adjust the Vortec distributor CMR as well without having to take it to a shop.

xc_hide_links_from_guests_guests_error_hide_media

Actually I don't even have to use a phone or tablet any longer. I have a 10" touch screen head unit in the Express that links directly to the Elm 327 device that stays plugged into the OBD2 port. I have a dash display built on the app that has a tach, long term fuel trims, commanded air/fuel ratio, knock retard, instant fuel economy, and trans temp. You can monitor practically anything in the OBD2 datastream. All have adjustable warning points. Hands free bluetooth calling and navigation maps.

http://vi.raptor.ebaydesc.com/ws/eB...4&pm=1&ds=0&t=1605833972000&ver=0&cspheader=1

My next additions are going to be the S10 steering wheel controls, backup camera, and tire pressure sensors.

For a tuner person that normally datalogs with HP Tuners its the coolest interior upgrade I have made to my 97 and it was less than $300.
What is it called though, the links are glitchy. But I am absolutely getting this. What do I search to find it. Sorry to be a necromancer
 
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