I accidentally put 91 Octane at 2500 miles on a taco that's used to 87

Disclaimer - I am not knowledgeable about the fuel relationship to an engine, compression, etc so go easy fellas and I will love you long time!

With that said, I am not used to pumping 87 because all my past vehicles for over a decade now have been 91, but I wasn't thinking today and have never used 91 Octane on my new '18. I've always put 87...now I know the manual says 87 or higher, and I don't care about performance, mileage or anything of that sort, so this is not a fuel discussion of that type, but rather a question about the following:

- Why does the manual say "Fuel Type: 87 (Research 91 octane) or higher"?
- When you start using one fuel type, is it true that you must stick to it and not flip flop back 'n' forth?
- What do they mean "Research 91 Octane"?
- What are the draw backs of accidentally putting a higher octane on a vehicle used to 87?
- Does this mess with the ECU's learning at this stage (2500 miles)?
- Can I switch back to 87 after this tank?
- If so, can I wait until I'm on Empty or should I dilute it with lower octane 87 at the half way point?
- With higher octane, does the engine run harder? Hotter?
- Does it put stress on the engine or does the ECU manage this?
- Does my ECU get confused now and need to learn my fuel type WITH my driving habits?

I know I'm over thinking this, but part of this is a learning experience, and the other part is that I would like to sleep tonight, can you guys help me sleep tonight lol! Thanks in advance!

Again, I don't care about performance, mileage or anything other than not hurting my engine, EVEN if the manual says its ok...some of you guys have better experience, plus the manual doesn't say whether you have to stick to one or can flip flop.

 

-Minimum is 87, can use higher if you want
-No
-No idea
-Spent more money than needed
-Doubtful
-Absolutely
-Up to you man
-Not that I know of
-From what I've read, the ECU advances timing when you put higher octane in, then lowers it when you put lower octane in
-Nah

Check this thread out for some comedy: https://www.tacomaworld.com/threads...t-but-hear-me-out.554230/page-5#post-18076481

 

I think youre over thinking it honestly. Putting higher octane gas in something that doesnt require it, is just throwing money away. Only high compression engines that are tuned for higher octane benefit from it because the piston can compress a higher octane fuel and air mixture without preignition happening. If you put 87 in a sports car that requires higher octane, you get preignition and it runs like shit. The piston detonates before it hits the top dead center of its cycle because lower octane fuel cant be compressed as much as the higher octane can. Thus you lose potential hp and get worse gas mileage. Some newer cars can actually take anything with the computer adjusting. Its just stupid when you see fake ballers at the gas station buying 87 in their german luxury cars because theyre too broke/cheap to buy the higher octane they require

 

Google says RON (Research 91 octane) is everywhere but the US: https://www.etuners.gr/fuel/

ETA: Bottom line, don't worry about it. Fill it up with 87 whenever you want and go about your day, it's not going to hurt anything but your wallet by putting a tank of higher octane in. Some will say it makes their truck faster or smoother, others will say it doesn't make any noticeable difference. I've never wondered or cared since premium is on average .50 more per gallon so I don't get it, and my truck runs fine as-is.

 

Only thing that happens is the engine can run a bit more timing and you may feel a bit more pep. No big deal and you can run 87-89-91-92-93, hell you could pour 110 in if you could find it.

 

Your engine is an air pump. Think of a syringe, when u pull it back it draws in air (and fuel). When you push it in (with the tip closed), the air / fuel mixture compresses, just before the syringe closes fully, a spark plugs ignites the mixture sending the syringe back the opposite direction, drawing more fuel / air in and the process continues. Theres only so much you can compress this mixture before it'll combust under it's own heat / pressure, before the spark plug has a chance to ignite it. That's where octane ratings come into play, octane rating is basically how much you can compress it untill it ignites on its own. On high performanc engines, the heat / pressure inside the "air pump" are greater and require a higher octane rating. On our engines, 87 (the lowest as far as I know) is fine. If you run higher, it just means it's less prone to self combustion, the spark plug will still do it's job as it was told. This turned into a long ramble. Hope it helped

 

Guys for the record my goal is not to run 91, so throwing away money or not really doesn’t matter to me at the moment, rather how it affects my engine when an accident like this happens and I want to go back, so I am asking from a technical stand point, not performance or MPG gains or losses, but you guys are right about that, why do it if it’s not a high performance engine...I knew what I was getting into when I bought the truck and it wasn’t about getting mileage or speed.

 

Not a ramble, you just seriously educated me. The longer the explanation the longer and better I will sleep tonight! Thanks guys!

 

Saw this thread and decided I didn’t want to hear him out lol, was happy with 87 for as long as I own the vehicle. The cost difference is so small to me that I really don’t care about the money, just treating my truck right in the beginning for it to last me a long time!

 

It doesn’t matter what you run. The ecu will adjust any timing issues. You didn’t do any hurt to your motor or truck. You can sleep well

 

The only time I put higher octane is when I am towing and know ahead of time that my route will have steep grades. Otherwise, its ok to mix and switch based on your needs.

Edit: I’ve also mixed grades with no issues when the lowest is below 87, sometimes happens in places where they only have two choices like in Baja California - gas or diesel.

 

Nah you're good man, I wondered the same things you asked when I was younger. I was given a lot of bad info and didn't have the internet to figure it out on my own/ask someone, so I'd heard the same rumors you were asking about in your 1st post. I remember hearing at 16 that putting higher octane in=faster car, but meant you had to stick with it forever afterwards otherwise I'd F stuff up. Learned later on that unless the manual states higher octane, 87 is perfectly fine, and switching between octanes doesn't do shit except cost more money.

Yeah yeah I know some will say that putting 93 in will turn this boat anchor of a truck into a Corvette and get 300mpg, but I doubt it.

 

You can bounce back and forth with octane amounts any time at all and your truck will adjust as necessary. No worries there. Mixing octanes is fine. The truck will do what it needs to do to adjust and it'll be happy.

For what it's worth... when I run 87 in my 2nd gen (2014), I get pinging when going up hills until the auto trans downshifts (or until I force it to downshift if it doesn't do it on its own). When I run 91, I don't have the problem.

 

Lots of good points, also worth noting that gas stations usually only have 2 tanks, one with 87 and the other with 93. If you buy 89 or 91 it just mixes from both tanks to hit the midgrade octane.

Obviously if you get ethanol free gas it'll be from its own tank.

 

Your truck is going to blow up. I'm sorry.






























Seriously, nothing is going to happen. When you switch back, just switch back. The truck will take care of the rest.

 

Is this thread a joke?

 

From an engineering and practical view - nothing happened that would adversely affect your truck in any meaningful way when you ran 91. You can switch back to 87 any time.. or not, with no issues. Quit worrying and enjoy your truck lol.

 

your truck is fine....you can switch at will, its not going to harm anything...

regarding "research ocatane"

there are actually 3 octane scales......RON, MON, and PON.

RON = Research Octane (what they use in Europe)

MON = Motor Octane

PON = Pump octane (What we use in the US, you will see it listed on the pump as R+M/2)


now the fuel is all the same.....RON and MON are both measured octane values in a lab setting( but under different conditions), RON values are always higher than MON values.....PON is the average of the RON and the MON.


so:
87 Octane in the US = 91 Octane in Europe
91 Octane in the US = 95 Octane in Europe
93 Octane in the US = 97 Octane in Europe

the fuels are exactly the same, just measured differently

this also gives rise to the myth that they have higher octane fuel in europe, and that American stuff is "watered down"........its not......thats like saying 212*F is hotter than 100*C

 

Define "hot"....

 

Just don't put diesel in it and you'll be fine.