Premium Fuel in 5.3L. More power or placebo effect?

[SouthPawCO]

I ran one tank of 91 and didn't notice anything other than my fuel mileage decreased. It could have been I did not do as much highway driving but I will try another tank this week and see how it does. My truck only has 2,200 miles on it.

[crushNchowda]

Probably makes a few more ponies but nothing like running E85 will

 

It'll run smoother and eliminate knock & pinging & maybe get a tad better mileage on 93

[Travis Whitmore]

I would think with vvt and DI more octane would help. Also according to black bear the 5.3 does have relatively high compression.

 

I run 89 or 92 in mine. Heck, gas is under $2/gallon anyway.

 

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Edited February 12, 2016 by TeeDub21

[tnchevy]

I don't know how gas is priced in other areas of the country but in my neck of the woods the gap in pricing between reg/mid/prem has gotten wider and wider. I run 87 in my truck but I have to run 91+ in two of my motorcycles and there is now a 60 cent gap between reg and premium around here and some places is 70 cents.. Used to be 10 cents between grades. One thing I've noticed with my truck lately is that it has an osculating vibration when in park or with brake on at a stop light. I wondering if a higher octane will reduce this or if I need my engine shimmed. Always something with this truck!

[jamesonjc]

I have noticed locally that the price between reg and premium can differ anywhere from .99 to .35 locally here in ny. When it is below .50 - I buy , over .50 - I go with what my engine was tuned for from teh factory - 87

 

I do notice that using 91 or 93 octane my vehicle goes into v4 mode more often in all driving conditions.

 

Power, I really don't see a noticeable gain. Mileage, the money does not work out.

 

I lease the trucks (Gm employee) so I really could care less either way. Less cost for gas just means lower cost of ownership. If that is $500 a year over 2 years, I will keep my $1k

[Txjose]

I think its funny how we are arguing octane levels amd cost.....

 

 

Its a truck.... If you want fuel economy on regular buy a cruiz.

 

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[tnchevy]

Fuel economy is one of the reasons I bought my 2014 when compared to other trucks along with other people on here. I will not give up driving a v8 full size 4wd truck but if I can save money on gas then that is money I can spend elsewhere on my other toys.

[batman900]

Doing back to back mpg tests on the same daily commute using the same station "as I always have."

 

I was getting 18mpg average with the 89 I've been using since I got the truck, I reset the trip every fill up. Switched to a tank of 87 and got 15mpg average. Switched back to 89 and got 18mpg average again. Switched to 91 and still at 18mpg. This is mostly per the truck's screen but I have done some hand calculations and they are always so close to the truck that I trust it now.

 

I should add that on the 87 at about half a tank I actually started trying to baby the truck more to get the avg back up but it only went from 15.3 to 15.6 by the end of the tank by doing so. I had no long sitting times, storms etc. There is also only 1 stop light in my town and other than that I go 35 "through town" or 75 with cruise "on the hwy" - no traffic in either case..... ever.

 

Could have all been a fluke on the 87 but it does have me sticking with 89 for now. I'm used to paying for premium due to all my previous cars and was always the first to say that if it doesn't reccomend a higher octane fuel then it's a waste. It seems newer engines and DI is changing the game.

[Poppafeel]

I read, in owners manual,  5.3l is 87 octane or better.it also said to only use top tier gas.I know for a fact my 2018 5.3l gets better gas mileage and runs smoother on high octane.as the owners manual suggest 87 octane OR BETTER!!!that OR BETTER is more better.it’s no placebo.so either longer detonation or something is in high octane that makes an engine run better. V8 engine.

[swathdiver]

I have not driven a car yet in 30+ years of driving that did not benefit from higher octane fuel.  I've proven it over and over from Toyota, Kia, Volkswagen, Ford, GMC, Buick, Oldsmobile, Cadillac, etc.

 

A friend took up my challenge in his direct injected Tahoe and proved me wrong.  He ran 87 and 93 and saw no difference in mileage with his 5.3.  He does experience a difference in mpgs in brands of gas and like me, gets worse mileage when using Shell over Sunoco, Mobil or Chevron.

 

None of my aforementioned gasoline powered autos were direct injected.

[Z45]

from gm service...................

Quote

For high-performance vehicles that require premium fuel (91 octane or higher), fuels of at least this octane must be used. Using lower octane fuel may result in reduced performance, knocking, and/or permanent engine damage that is not covered under the terms of the New Vehicle Limited Warranty. Using higher octane fuels in a vehicle that only requires regular unleaded fuel will not increase performance or improve gas mileage. Only use the octane-rated fuel recommended as specified in the vehicle’s Owner’s Manual.