Should I run 87 or 89 fuel in my 2017 Silverado 1500 5.3L?

2014gmcAT · July 4, 2017

Im using only 91 for the last year. It's 7c/L more so it's only a couple dollars every fill up. I feel like I get a bit better mileage on the highway, but I spend too much time idling and at low speed to make up for it. I've seen nearly identical mileage through one year of using 91 exclusively and 1.5 years previous with 87.

I drove through the states last year and ended up using 87 due to the greater price gap and once on a steep grade at low speed the truck started knocking bad. Whether the cause was from octane itself or the computer unable to adjust I don't know.

Donstar · July 4, 2017

You reminded me of something I failed to mention. Not all fuels are created equal. I remember back in my tuning days, Shell caused unbelievable knock retard vs. other fuels. I wouldn't run Shell in a rented lawn mower.

Interesting! I believe that I once read in a similar topic on this forum that Shell was a preferred brand and is a "Top Tier" product. It is more convenient for me not to use Shell and you are telling me that it is not worth going out of my way to fill up with this brand of gas. (Like I fuelishly did yesterday) I know that the key difference between brands is the additives so I wonder what makes Shell stand out - good or bad?

Boardmember · July 4, 2017

I have zero explanation or hypothesis, but I have a similar avoidance to Texaco. Certainly no instrumentation, just "seat of the pants," but in a couple of my vehicles I've gotten a significant impression that they don't run as well or deliver comparable mpg when burning Texaco.

I'm not flaming, or in any way missing that Texaco is on everyone's "top tier" list, just not mine. Who knows?

All anomalies. And opinions. Everybody has one.

KARNUT · July 4, 2017

I was lucky to have plenty of E-85 stations locally when I had my 14, what a difference. On my many road trips I used all other brands looking for E-85 was a hassle. I got the same gas mileage 87-93 gas, so 87 chevron when I could.

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Silverado Steve · July 4, 2017

One chain of local gas stations here sells E-15 for 10 cents cheaper than 87. I might give this a go for a few tanks to see what returns i get...might be a nice balance from regular 87 and 89 for a cheaper price point.

Donstar · July 4, 2017

One chain of local gas stations here sells E-15 for 10 cents cheaper than 87. I might give this a go for a few tanks to see what returns i get...might be a nice balance from regular 87 and 89 for a cheaper price point.

I once did the same but discovered that this particular local brand wasn't on the top tier list

Silverado Steve · July 4, 2017

What kind of mpgs did you get? Im not so concerned about using top tier fuel

I once did the same but discovered that this particular local brand wasn't on the top tier list

KARNUT · July 4, 2017

I got about 4MPG less on E85, I gained 25HP and a more responsive better running truck. In my area Krogers grocery store carried E85 with a store card I got it cheaper than 87 gas. All things equal price wise I would have paid more for the HP gains and a better running truck. I even had a tune I ended up leaving the engine alone and turned off the V4 ( at best on gave me 1MPG) took 50 per cent off TM. The truck was as fun to drive as some of the performance rides I've owned at 61 I had and have a few.

Silverado Steve · July 4, 2017

Yeah ive run E85 but the mileage was crap. Was worth it when gas was over $3.00/gallon, with gas being as cheap as it is, outside of the power boost, E85 isnt worth it. Seeing how E15 formulation is close to 10 cents cheaper that 87 and the octane rating is 91, it seems like a deal; especially if mpgs are within 5% of regular 87.

KARNUT · July 4, 2017

In my area E85 is always cheaper than reg gas. My in town gas mileage was about 4 MPG less. My net was sill cheaper and got 25 HP to boot. For people who worry about KR and run higher grades E85 is a win-win. For A-B drivers with no E85 option reg gas will work. I'm an enthusiast so appliance driving is not for me.

Donstar · July 4, 2017

What kind of mpgs did you get? Im not so concerned about using top tier fuel

My driving varies so much, I really don't track my MPG but I often keep my DIC on this setting. I am looking forward to trying E85 someday when travelling south!

gmckenzie · July 4, 2017

I find the v4 mode annoys me less running 89 than 87. I'm not sure why, it could all be in my head, but it's worth the extra for me to run 89.

LyleLukas11 · July 4, 2017

A stock OEM motor should never knock on any level of fuel 87+. The knock sensor is there so if u run some super shitty watered down gas and there are problems.

If you go to any Shell or Mobil you will be fine. The difference in octane between 87 and 89 is so obsolete it isn't even funny. So to the people that say they see a drastic difference is total bullshit.

I run race cars on all levels of gas. Now 93 vs 87 will have some difference but minimal. Real difference is E85, have an ecu tune for that and it's octane level is rated at 105, but you have to dump 20pct more. But it runs cooler and you can make bigger power.

So drop the bullshit between 87 vs 89.....

JRoyPDX · July 4, 2017

The only way to know if you should step up fuel octane is to datalog and see if it is picking up angry kick and any timing is being pulled out because of it.

Adding higher octane won't add power by increasing timing unless timing is being pulled out because of knock retard in the first place.

And I read the thread comments, it looks like that's already been covered, lol

Orlando8 · July 4, 2017

A stock OEM motor should never knock on any level of fuel 87+. The knock sensor is there so if u run some super shitty watered down gas and there are problems.

If you go to any Shell or Mobil you will be fine. The difference in octane between 87 and 89 is so obsolete it isn't even funny. So to the people that say they see a drastic difference is total bullshit.

I run race cars on all levels of gas. Now 93 vs 87 will have some difference but minimal. Real difference is E85, have an ecu tune for that and it's octane level is rated at 105, but you have to dump 20pct more. But it runs cooler and you can make bigger power.

So drop the bullshit between 87 vs 89.....

Amen