If it'll run on 87, but 91 is recommended . . . what happens if you put in 93?

[00 Trans Ram]

If you put higher octane in a regular engine than is recommended, it's a waste of money. But, most engines that call for higher octane can't run well on lower. However, our H/O pulls timing at lower octanes and you can run it, except with lower power output.

Where I am, we don't have 91 octane. Just 89 and 93. I suppose I could put in half 89 and half 93 if I wanted to save some money. But, will it perform even better on pure 93?

My guess is "no", but it's just a guess.

 

[John Kloehr]

Run a few tanks of the recommended, and calculate the true mileage (not the dashboard guesstimate) Also keep the receipts, and calculate the cost per mile.

Do the same for the acceptable lower octane. If you are happy with the power, and it does run OK, calculate the true mileage and cost per mile.

Your thread title says 87, your reference 89 and 93 as your choices. So repeat for the 3rd option.

My 5.7 '22 Rebel has 87 listed as acceptable and 89 recommended. I did these tests/calculations and found out I can run either for the same cost per mile. I did not notice a difference in power between them, the recommended octane did provide a bit better mpg. Combine with the higher cost per gallon, it was a wash. So generally I am using regular but would likely switch to mid-grade if I was going to tow; rather not pull timing if I am going to have a higher load.

Any octane higher than recommended for your vehicle is a waste of money, blending might get you close but would be a nuisance IMO.

 

[Bigtone]

If you put higher octane in a regular engine than is recommended, it's a waste of money. But, most engines that call for higher octane can't run well on lower. However, our H/O pulls timing at lower octanes and you can run it, except with lower power output.

Where I am, we don't have 91 octane. Just 89 and 93. I suppose I could put in half 89 and half 93 if I wanted to save some money. But, will it perform even better on pure 93?

My guess is "no", but it's just a guess.

I'm in the same boat, not many places have 91 octane, so i run 93. There is alot more to it than just checking your mpg numbers with different octanes. With lower octane, the pcm will bump the timing back, but that may also increase combustion temperatures. Some of the early HO's were cooking catalytic converters, and I wonder it that may have been due to using lower octane fuel. Also, I'm told that the dealer can see if the spark map has been retarded for an extended period and may jeopardize the warranty if a claim came up.

 

[Diesel]

Pump all the 93 you want, it will thank you for doing so

 

[jjax402]

I personally only put 93 octane in mine... better combustion

 

[Scap]

Boosted applications love higher octane.

Not sure if you can run E85 in these, but that's damn near race gas for forced induction when you have enough fuel pump and injector volume and a proper tune to dial up the timing and boost.

 

[LOWRMPG]

If you put higher octane in a regular engine than is recommended, it's a waste of money. But, most engines that call for higher octane can't run well on lower. However, our H/O pulls timing at lower octanes and you can run it, except with lower power output.

Where I am, we don't have 91 octane. Just 89 and 93. I suppose I could put in half 89 and half 93 if I wanted to save some money. But, will it perform even better on pure 93?

My guess is "no", but it's just a guess.

The lowest you should ever run is 91. If you can't afford 91, you shouldn't have bought the truck. I've only ever run 93.

 

[UnloosedChewtoy]

If you put higher octane in a regular engine than is recommended, it's a waste of money. But, most engines that call for higher octane can't run well on lower. However, our H/O pulls timing at lower octanes and you can run it, except with lower power output.

Where I am, we don't have 91 octane. Just 89 and 93. I suppose I could put in half 89 and half 93 if I wanted to save some money. But, will it perform even better on pure 93?

My guess is "no", but it's just a guess.

If you put in 93 octane, your engine will overheat and explode. That's way too hot of gas to use.

Just teasin.

As LOWRMPG (that's a great username BTW) and others said, minimum is 91. If its available, I'll use the higher octane, because sometimes gas stations cheat in my area, especially if their next state inspection is a way off. The distributors have been caught before putting in 89 into the 91 tanks, 87 into the 89, and 85 into the 87. Their excuse is always "we were afraid we would run out and the elevation is high enough here for lower octanes", which are both crap excuses/lies.

So by putting in the next higher octane where available, if the gas station cheated a little, I'm hopefully still getting high-enough octane. Am I wasting a little money? Maybe, but its worth my peace of mind.

 

[00 Trans Ram]

I guess I should have been clearer. I'm NOT putting in 87 or 89. I would only use what's recommended.

But, the factory obviously designed them with the ability to adapt to lower octane by pulling timing and making other adjustments. What I'm wondering is if the factory might have said, "A lot of places have 91 as their highest, but a lot also have 93 as their highest. Let's design it for 91, but make it possible to get even more with 93."

I would assume that if they did that, they would brag about it. But, I've seen LOTS of manufacturers understate the capabilities of their cars, just because they don't want the hassle of proving the other claims (or liability, or whatever).

In other words, I'm just kinda curious if I'm seeing 540hp or something a bit more. Mainly just curiosity - wouldn't really change my activities or anything.

 

[Scap]

I guess I should have been clearer. I'm NOT putting in 87 or 89. I would only use what's recommended.

But, the factory obviously designed them with the ability to adapt to lower octane by pulling timing and making other adjustments. What I'm wondering is if the factory might have said, "A lot of places have 91 as their highest, but a lot also have 93 as their highest. Let's design it for 91, but make it possible to get even more with 93."

I would assume that if they did that, they would brag about it. But, I've seen LOTS of manufacturers understate the capabilities of their cars, just because they don't want the hassle of proving the other claims (or liability, or whatever).

In other words, I'm just kinda curious if I'm seeing 540hp or something a bit more. Mainly just curiosity - wouldn't really change my activities or anything.

See if you can find a local shop with a "heartbreaker" dyno and strap it down for a couple pulls.

 

[Quint]

You won't see any tangible gains from the truck. All the gains will be in your mind and the losses will be in your wallet.

For those talking about running below the recommended (87 octane), I believe that the manual says that if you hear knocking then to run 89 (or 91) - whatever is recommended. I ran 87 in my 2015 RAM with no problems. Ticking started around 80k miles and then the cam & lifters needed to be replaced. My 2021 has gotten 89 octane from Day 1 unless it wasn't available. I also run E15 (88 octane) when I find it, as the manual says that is fine as well. On occasions where the gas station only has 87 and 91/93, I have pumped half of each. The gas stations just mix the two anyway. It's not like they are getting 89 octane hauled separately to their station.

 

[Scap]

You won't see any tangible gains from the truck. All the gains will be in your mind and the losses will be in your wallet.

For those talking about running below the recommended (87 octane), I believe that the manual says that if you hear knocking then to run 89 (or 91) - whatever is recommended. I ran 87 in my 2015 RAM with no problems. Ticking started around 80k miles and then the cam & lifters needed to be replaced. My 2021 has gotten 89 octane from Day 1 unless it wasn't available. I also run E15 (88 octane) when I find it, as the manual says that is fine as well. On occasions where the gas station only has 87 and 91/93, I have pumped half of each. The gas stations just mix the two anyway. It's not like they are getting 89 octane hauled separately to their station.

This is a turbo engine, so anecdotal V8 stories likely don't apply in this scenario.

 

[LOWRMPG]

You won't see any tangible gains from the truck. All the gains will be in your mind and the losses will be in your wallet.

For those talking about running below the recommended (87 octane), I believe that the manual says that if you hear knocking then to run 89 (or 91) - whatever is recommended. I ran 87 in my 2015 RAM with no problems. Ticking started around 80k miles and then the cam & lifters needed to be replaced. My 2021 has gotten 89 octane from Day 1 unless it wasn't available. I also run E15 (88 octane) when I find it, as the manual says that is fine as well. On occasions where the gas station only has 87 and 91/93, I have pumped half of each. The gas stations just mix the two anyway. It's not like they are getting 89 octane hauled separately to their station.

This is about the 3.0 HO, not a 5.7.

 

[LOWRMPG]

I guess I should have been clearer. I'm NOT putting in 87 or 89. I would only use what's recommended.

But, the factory obviously designed them with the ability to adapt to lower octane by pulling timing and making other adjustments. What I'm wondering is if the factory might have said, "A lot of places have 91 as their highest, but a lot also have 93 as their highest. Let's design it for 91, but make it possible to get even more with 93."

I would assume that if they did that, they would brag about it. But, I've seen LOTS of manufacturers understate the capabilities of their cars, just because they don't want the hassle of proving the other claims (or liability, or whatever).

In other words, I'm just kinda curious if I'm seeing 540hp or something a bit more. Mainly just curiosity - wouldn't really change my activities or anything.

If they could advertise more HP/TQ because someone put 93 octane in it, they'd use that a selling point.

 

[silver billet]

If they could advertise more HP/TQ because someone put 93 octane in it, they'd use that a selling point.

The engines rated hp is always at the "recommended" octane level. If you run the lower octanes, even if they are approved for use, they won't get rated HP/Tq figures. Nissan gave exact amounts at different octanes, but it doesn't really matter because they all work the same way: full rated hp at recommended octane, special "microphones"/sensors listen for knock/ping and detune when they hear it, which gives you less than rated power.

So think about that. Would you rather put in the right gas that doesn't cause knock/ping in the first place, or would you rather the engine keep on trying to tune itself for the higher octane, and listen for "bad things happening"? Because that's how it works... the truck is constantly trying to tune for the proper gas, detects knock/ping, retards timing, then eventually tries again to tune for the higher octane etc etc.

I put in 91, because it makes a difference while towing. Even with 89 octane you can't be sure the guy before you put in 87 so you get left over junk gas from the hose etc. And once I stopped trying to play chemist and just fed it 91 constantly even when not towing, the truck eventually settled down and I never hear anything anymore. Took a few tanks before I noticed I wasn't hearing it.

 

[Jako]

The engines rated hp is always at the "recommended" octane level. If you run the lower octanes, even if they are approved for use, they won't get rated HP/Tq figures. Nissan gave exact amounts at different octanes, but it doesn't really matter because they all work the same way: full rated hp at recommended octane, special "microphones"/sensors listen for knock/ping and detune when they hear it, which gives you less than rated power.

So think about that. Would you rather put in the right gas that doesn't cause knock/ping in the first place, or would you rather the engine keep on trying to tune itself for the higher octane, and listen for "bad things happening"? Because that's how it works... the truck is constantly trying to tune for the proper gas, detects knock/ping, retards timing, then eventually tries again to tune for the higher octane etc etc.

I put in 91, because it makes a difference while towing. Even with 89 octane you can't be sure the guy before you put in 87 so you get left over junk gas from the hose etc. And once I stopped trying to play chemist and just fed it 91 constantly even when not towing, the truck eventually settled down and I never hear anything anymore. Took a few tanks before I noticed I wasn't hearing it.

I buy Costco which has 93 and 87. I do 1/3 93 octane first and then 2/3 87 octane next so I don't leave the 93 in the hose.
Quick math off the display:
miles/mpg=gallons
gallons/3=my 1/3 93 octane
fill the rest with 87

Today at Costco :
169.3 miles at 9.6 mpg
169.3/9.6=17.64 gallons
17.64/3=5.88 gallons of 93

I stopped the pump at 5.780 gallons with 93 at $4.059 gallon
and put in 11.415 gallons of 87 at $3.749 gallon

Works out to 89.03 octane at $3.852 gallon

$64.46 for 87
$66.24 for 89 $1.78 more if I used 87 and $3.55 less if I used 93
$69.79 for 93

Note that the differential for 93 and 87 on this fill up was only $.31/gallon. I have recorded differentials up to $.80/gallon which would be some hit if filling up an empty tank with all 93. NJ Costco 93 is lower then NY 93 and a very good price compared to other brands. NJ bans self service but isn't enforced at this Costco so I pump my own.
.
I have also found 89 octane is cheaper if you "blend" your own versus pumping 89 at the pump. Last time I did the math I believe it was 10 cents a gallon. Paid for my coffee.

After 51,000+ miles on the odometer doing the math is 2nd nature to me and keeps the synapses firing.

 

[Granite Goat]

Put some 104 octane in and it'll accelerate so fast your face will part and slide off the back of your skull... or not... maybe

 

[CalvinC]

I “can” run on McDonalds 3 meals a day.

But I may not be operating at my peak.

Modern boosted engines are pretty cool in how they can reward higher octane. For ages now engines have had variable timing, and finally there is some tangible benefit to that complexity.

But I don’t think the advantage will ever lie in cost per mile, but rather in enjoyment.

Think about this: higher octane allows your engine to run more advanced timing. That allows the engine to achieve the same given power output with less boost.

Something to think about for the “boost is bad” crowd.

But where the fun starts is when you DON’T dial back the boost AND you can still advance timing. This is what modern engines now do, and why octane makes a difference you can actually detect, unlike N/A engines where there is no boost part of the equation.

And if you think that is cool, allow me to introduce you to Mr. Ethanol…

 

[CobraKai]

I'm in the same boat, not many places have 91 octane, so i run 93. There is alot more to it than just checking your mpg numbers with different octanes. With lower octane, the pcm will bump the timing back, but that may also increase combustion temperatures. Some of the early HO's were cooking catalytic converters, and I wonder it that may have been due to using lower octane fuel. Also, I'm told that the dealer can see if the spark map has been retarded for an extended period and may jeopardize the warranty if a claim came up.

As one of the early HO trucks whose cats melted at 5000 miles I can assure you it's not from lower octane gas. I Only run 93 or higher in mine, 94 most of the time from Sunoco...

 

[Ripper]

Do I dare bring up the topic of Top Tier fuel and if it is worth the extra $ in most cases. Personally I look for top tier fuel and in my area that means running Mobil, Shell, Sunoco or Costco for the most part.