87 vs 91 Octane?

Will you be filling up using 87 or 91 octane moving forward?


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tRex

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What I WILL do is use Top Tier gas, and I think install a good oil catch can ("separator") setup. DI engines are terrible for carbon and sludge deposits on the valves and pistons, because a.) they are not constantly washed by a port injector, and b.) because of all the recirculated oil and unburnt fuel being pumped back into the intake by the PCV system. (PCV relieves pressure buildup in the crankcase, but for emissions reasons also recirculates all that gunk to be burnt by the engine instead of just released into the atmosphere). An even bigger problem on DI-only engines with higher compression ratios and turbo (more blowby in the cylinder). So blow it all into a catch can instead, and empty that once in while, better than burning it. Top Tier gas -- it's a program to assure that the gas has the correct detergent additives in the correct proportions to burn the cleanest.
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tRex

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But...I'd say to anyone and do so myself -- if you're getting more than the occasional pinging, switch to 91+ octane. The engine/computer have their limits and, it's really dependent upon your driving habits in the end.
 

wiyeti

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Given 91 octane premium is about 75 cents on average more in WI, I'll stick with the 87 top tier. The mild benefits are not worth the added cost.
 

o0260o

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The manual recommending premium is a bit odd. I'd like to see the BS on the dyno with a tank of 87 and 91.
 

13MikeH

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personally...I had an old Ranger I bought new. I took a trip to Florida, always ran 87 octane. The station I filled up at only had 93 available. I did what I had to do...half an hour later the warning lights came on. Took it to the dealer down there, blew all my O2 sensors with the rich gas and lower altitude. They strongly recommended I stick with recommended octane levels...haven't changed it since. Even in my challenger, I use 87, that's what's on the fill door, it motors just fine with what it's tuned to. Why waste an extra dollar a gallon or more for nothing noticeable and risk damage to components? I guess I really am old.
 


WoodmanMN

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The reason I use Premium (91 octane is all that is commonly available near me, I believe two stations have 92, but are not close enough to make it worth driving there for gas) is because in my area, most 91 is non-oxygenated. That means better MPG, and I prefer to use what is recommended for the motor. My daily is a 2003 Acura RSX (base), and it gets a steady diet of 87, gets 30ish mpg every tank (except when it's -20F here, but no one gets good MPG up here on winter blend fuel). No, running 87 won't hurt anything, probably won't directly affect MPG, but for the extra couple of dollars a tank, I'd rather put non-oxy gas in.

My Thunderbird is tuned for 91 thanks to the better cams, headers, etc. It's also more of a smiles per gallon car, but even with 3.73 gears in it, I'm expecting 23-24mpg on a steady cruise once it's back together.
 

JAD67428

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I want mine to last for at least 150000 miles so mine will only see 93 octane, to much of a pain to go looking for 91 around here, especially for this little 3 cylinder.
 

Osco

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I want mine to last for at least 150000 miles so mine will only see 93 octane, to much of a pain to go looking for 91 around here, especially for this little 3 cylinder.
You said that backwards right ?
If you have the 1.5L you’ll get a longer service life with the 87 octane. If you need the higher antiknock chemistry of the 93 something may be wrong,,,,,
I have in the past vehicle after vehicle put on crazy high mileage.
For example:
Tacoma 4 bangers, took one to
528,000. Another to 430,000, totaled that one, it was running fine. Another 22R 340,000 and the guy who bought it for $700 got 100,000 more.
Fords 2013 F-150 V-6 167,000 and my salesman bought it from me personally. Ranger 4 banger 380,000.
Jeep Cherokee with the straight six 4 L converted to fuel injection. This motor was designed and built in 1957. The mains let go at 395,000.
ALL on the cheapest 87 octagon I could find.
ALL server duty commercial use,
ALL at or above 90,000 miles a year in the Florida heat, humidity and interstate and city traffic jams,
Again ALL on 87 octane…
Just sayin.
 
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MaxVelocity

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69cuda340s

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ECU will adjust fuel and timing for 87 octane that is all engineered in. If I was going to tow I would prob put some higher octane in there esp in summer. Mine seems to pull plenty strong running 87. I not looking to stomp the pedal to the floor all the time.
 


Orin

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If you read the owners manual closely it says 91 Premium or higher recommended...BUT it will run on 87 Octane. It also says all the testing numbers of MPG/HP/Torq numbers published were all done with 91 premium. I may pay an extra $8 - $9 at each fillup it don't bother me. I pay more than that going to lunch at Taco Bell which I go alot :)

Edit - Also want to add that the manual on my Toyota says 87 octane recommended BUT will run on higher octane. So on my Toyota I use 87. Every engine will run whatever octane I understand that but I like to go by what is recommended. I'm also the rare breed that reads owners manuals on everything I buy!
 
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Tom 5778

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And if your car sits longer between fill ups the premium should hold up better and not degrade as quickly, correct? It’s also better for the longevity of the turbo (From what I’ve read). Not an expert by any means.
I recently moved to Florida where ethanol free gas is an option. It is all I put in my Cobra replica. With my BS I don’t worry about ethanol infused gas sitting long enough to go bad.
 

Tom 5778

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Let me see if I can get this right.
If I pay $2.90 a gallon for ethanol free as opposed to $2.05 my 27 mpg Baby Bronc will get 33 mpg ?
I really doubt that.
I did finally try a tank of premium fuel.
Felt no diff in power, even in sport mode.
Unless I mashed the gas harder dropping my avg mpg some...
Not science, only one try of a half tank but:
Tank of 87 octane. 26.1 avg mpg
Tank of real gas, 91 no eth, got me 26.3 avg mpg. But The roads were dryer meaning less rolling resistance during that fill up.
,
As. Forum group we owe it to ourselves to do a mileage thread based on octane and non ethanol vs ethenol.
In several of my older 4 and 6 cylinder smaller engine vehicles I saw no gain in mpg or felt better response with premium.
The slower flame propogation of higher octane that is simply more anti knock compound can help in very hot weather and or heavy loads as far as I can tell. A bit of this is in the owners manual....
I had a dual fuel Ford Explorer. If I ever used E-85 (I tried it a couple of times at one of three E-85 stations in Maryland). i don’t remember how big the mileage drop was, but it was significant. But otherwise I don’t think there’s much difference with 10% ethanol.
 

Badwolf13

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I have been running 91 octane in it since I bought her back in December. There is a difference in drivability and mileage, I don't mind the little extra that it costs.....but that's just me.
 
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Mark S.

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If you read the owners manual closely it says 91 Premium or higher recommended...
Okay, I'm going to get technical on you, but this is a technical discussion so it's best to be precise. The manual doesn't say premium is the recommended fuel. Here're the two salient quotes:

Your vehicle is designed to operate on regular unleaded gasoline with a minimum pump (R+M)/2 octane rating of 87.
and

For best overall vehicle and engine performance, premium fuel with an octane rating of 91 or higher is recommended. The performance gained by using premium fuel is most noticeable in hot weather as well as other conditions, for example when towing a trailer.
This is not a recommendation to use premium fuel, it's a recommendation to use premium in driving situations where you need the most engine performance, such as towing. Unless you always like to be first to the next stop light (you know who you are), or you frequently drive on two-lane mountain roads where you need gobs of passing power, you will likely not notice any difference in the way the vehicle performs between regular and premium. Premium only matters when the throttle is at or near wide open, when power demand exceeds what the engine is capable of producing on regular gas.

Unless you need the additional 20-30 horsepower available burning premium, save yourself some money and use regular (remember: minimum 87 octane) with confidence. It will not harm the engine in any way, nor will it significantly impact fuel economy. In some situations you may even get better fuel mileage using regular.
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