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Wrong Gas Octane

14K views 44 replies 25 participants last post by  2012 2.5premium cvt 
#1 ·
My wife accidentally put about 9 gallons of 93 Octane in our new 2.5 Outback with 600 miles on it.
Will going back to 87 Octane cause any problems?
 
#2 ·
Sorry, you are now committed to 93 octane for the life of the car... ;)

Perfectly fine. Issue could arise if for example you had a turbo that required 93 octane and you put in 87. Even with that scenario, I would think it'd have to be multiple times. In our cases where the Outback takes 87, you're ok using 93 and then going back.
 
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#6 ·
I am morbidly curious as to how many posts this thread will generate from 2015-17 people in the next 24 hours. :drama:
 
#4 ·
I think you need to stop driving the car immediately and have it towed to the dealer. Tell them what happened and tell them you want the tank drained. Don't accept no for an answer!

:grin2:

Course, I'm lying out my a$$

It's perfectly fine. It would only be a problem if the car required 93 and she put in 87. Putting in 93 when it requires 87 only means she paid a lot more than what was necessary. And since she didn't completely fill the tank, any benefits from the higher octane will be minor at best.
 
#35 ·
It would only be a problem if the car required 93 and she put in 87.
That's not much of a problem either. You won't get the rated performance out of the engine, but for everyday use you probably won't notice the difference. The engine controller will make adjustments and move on down the road.

Had a 2001 Audi and a 2005 Acura both of which "required" premium. Put regular in both for extended periods. Didn't hurt a thing.
 
#5 ·
Find a new wife with reading comprehension skills if you desire but otherwise, you're a little poorer and that's the extent of the harm.

No harm and no foul by going back to 87. Just wait until you take a trip into CO or UT where they sell 85 octane and then we can really talk about octane requirements at elevation, hot days and at sea level.
 
#10 ·
well did you do the chivalrous savior like thing: walk into the station and buy her a bottle of octane booster? as apparently she knows not what such stuff is 0:)
 
#9 ·
No harm. However, i am curious. Did you not learn anything about car techology as a teenager? :) My generation (old) learned to turn a wrench at a pretty early age.
 
#24 ·
I ran into a situation yesterday, that had me asking a similar question. On day two with my Outback I was pulling into a parking lot and there was car with its hazards on blocking traffic causing a bottle neck on an slight grade. Of course no one was helping the kid I parked my car up the hill. I went down to help push, first I had to explain to him that he needed to stay up front with his hand on the wheel, and I would push from the trunk. He told me he was new to cars and his car had a temporary plate, so he just got the car. Another Samaritan came along a helped me push, and when we got to the top we both heard the kid tell his dad on the phone.

"It must be the gas I put in, that is the only thing that has changed, I refused to believe it, but the guy who joined in helping, immediately opened the gas lid and asked me to smell, and it reeked of diesel (just for accuracy it wasn't a diesel vehicle).
 
#17 ·
Based on how some people's cars are kept I'd settle for some basic common sense beat into people.

We had a neighbor who was asking for help their monster Ford SUV wouldn't start. I was volunteered to help (since I was on break between semesters), I grudgingly got out of bed and took my parents Taurus next door knowing it had a good selection of tools & emergency supplies in the trunk.

First problem, they had no jumper cables. Dug those out...hooked them up. Ran our car for 5 min or so and tried to start their SUV - barely a click and the lights went out while trying to crank. Went home and dug out a meter...their 12Vbattery was about 5V with the jumper-cables connected (but 14V at the battery clamps). Even the 6AWG "extra heavy duty" jumper cables had too much volt-drop when pulling hundreds of amps to crank. Took the clamps apart and cleaned massive corrosion. Put it together, hooked up jumper cables...didn't even need the meter I could tell it was charging from the big spark making the connection to the engine-block and hearing our car's engine bog down as the alternator carried the sudden heavy load. Sat holding the accelerator at 3500RPM for another 5 minutes to charge their flat battery...then went and tried to start their SUV. After a few false-starts it finally started up but made awful squeaking noises, shut it off. Check oil...it's got midnight-black dirty oil at the bottom of the dipstick in the "add" range. Check their coolant...expansion tank empty. Engine is still cold so I pop the radiator cap...bone dry. At least they had power-steering, brake, and transmission fluid. Put everything away and drove them to the auto-parts store (under their protest "do I really need to buy coolant and oil right now"). Added oil to get it near the top of "full", filled the radiator and re-jump-started their car. Then went back to pouring in the pre-mix coolant (because I was so done with this I made them buy that to make my life easier). Took 1.5 of the pre-mix jugs to get the radiator where it started circulating brownish crud and was at least full up to the cap, then put the cap on and filled the expansion tank to the "full cold" mark. I sent them on their way with the warning that they needed to immediately get a new battery without shutting the car off until they get to the shop and also looked like they needed a coolant flush and oil change as well as checking why it lost it's coolant...I fully expect they did none of those things but at least it was no longer my problem.

To this day I don't know if I should be appalled at their maintenance or amazed at the Ford V8 engine for not seizing since I got the impression they had been driving it for days (or maybe months) like that.

And to think, I investigate when I hear any little squeak, whistle, etc. and get worried if the fluids drop even half way down the "full" range between service.

Sorry about that long tangent.
 
#14 ·
Using fuel with a higher AKI (anti-knock index, a.k.a. "octane") rating than specified by the vehicle manufacturer is not likely to hurt anything but your wallet. There are no problems associated with mixing gasolines with different AKI ratings.

I am morbidly curious as to how many posts this thread will generate ...
42.
 
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#22 ·
Unless you're racing the car, you won't notice any difference between 87 and 93. Next time you're at the gas station you could add 1/3 of 87, 1/3 of 89 and 1/3 of 93 and it wouldn't make any difference except to your wallet. And other patrons might give you funny looks. And after using the third pump your credit card might get declined as it triggers a potential fraud alert.
 
#26 · (Edited)
Rule of thumb: "the lower the octane fuel used the higher the fuel consumption"

Proved this with my 06 3.0R S I Drive using regular fuel (full tank) - fuel consumption 2mpg less compared to using premium (as recommended by Subaru - manufacturer) and using trip computer in economy mode to see what was actually happening.

3.0R engine specs set up to run best on premium ie 10.5:1 compression ratio and ignition timing 15BTDC
Engine management system working overtime to stop denotation when using regular fuel - hence more fuel used.

Car driven similarly in both cases of fuel used ie distances speed load etc.

Why the penny pinching for the price difference of a decent cup of coffee? - for a full tank of fuel. ie using regular when premium recommended by Fuji Heavy Industries Japan the makers of Subaru ( in this case for 3.0R)
 
#27 ·
Rule of thumb: "the lower the octane fuel used the higher the fuel consumption"
Better rules of thumb: 1) Higher compression ratios yield higher engine thermal efficiency. 2) In spark-ignition engines, higher compression ratios require higher fuel "octane." 3) For a given compression ratio, higher fuel "octane" allows greater spark advance, which tends to increase engine efficiency. Using lower "octane" fuel usually requires retarding the ignition timing.
 
#40 ·
no.



however, some recent tests done by AAA have convinced me to use only top tier gasoline. see list here



top tier gasoline Archives - AAA NewsRoom



"YMMV" :smile2:


Thank you for the info. My situation may be related.

Sometime, I have to buy no-name-brand gasoline because of the location. Most of the time, I can not detect a difference but once in a while I experience the following.

The car is a bit sluggish during pickup. But the mileage in within 5%.

Can it be due to

A. Lack of additive
B. Lower octane

Thanks.


Sent from my iPhone using Tapatalk
 
#37 ·
Custom tune a WRX on 93 you better continue to use it... :)

When I had my WRX I would hook up my AccessPort and look for knocking here and there just to be safe. It is an interesting process logging the engine and see how far you can safely advance the timing.

The difference between 87 and 93 tune was as much as 25HP.
 
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#38 ·
It would be interesting to see some dyno tests done with different cars
ie standard family saloon /wagons vs performance cars
ie between octane value / use and horsepower differences / output if any / much?

Perhaps this link answered this question

Regular or Premium? - Feature - Car and Driver
 
#39 ·
There may be no energy difference in the different octane ratings however, the way gasoline is blended and sold is such that mid-range can have more energy than regular, and premium more than that.

Here's why. In Ontario, auto fuel retailers are required by law to add ethanol to their gas such that ethanol comprises 5% by volume of what is sold. Some retailers (Shell is known to do this and sometimes even indicates it on the pump) don't simply dilute it all 5% but in fact dilute the regular 10%, mid-grade 5,and premium none. In this situation, since ethanol has lower energy density, the higher grade gas will have more energy, but it's because of the ethanol, not the octane.


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#43 ·
Top Tier is not the same thing as high octane. Rather it's a standard for gasoline using certain additives that, in theory, are better for your engine. Thus there are potentially reasons to favor Top Tier gas, as your mechanic says, but there's no relation between meeting the Top Tier standard and octane rating.

Straight from the horse's mouth:

all grades of gasoline sold under the licensed brands listed below must meet the high standards of TOP TIER™ Detergent Gasoline.
Fortunately for you, most major retailers now sell Top Tier gas.
 
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