Hooniverse Asks- What's Your Octane?

Everybody likes the Rolling Stones. But when your engine starts singing Can’t You Hear Me Knocking? it may be time to switch up your grade of gas. With prices climbing a good ten to twenty cents per gallon when doing so, that can really add up to emptying your bank account while filling your tank. So what grade of gas makes the grade for you?
Now, you diesel owners out there will just have to sit on your hands today, this is for the folks living on Gasoline Alley. I, like most of you, have nothing but gas-burners, and one of my rules of thumb is to never have a daily driver that uses anything more dear than regular. Sure, the fun cars need premium, but for cruising the Junior High doing errands or slogging to and from work I want something that burns the cheap stuff.
That cheap stuff here in So Cal is 87 Octane, and there’s typically two upgrades from that – 89 and 91. Some 76 stations used to carry 100 race gas, but I haven’t seen that outside of a track for a while- not that I was looking.
Elsewhere in the country, notably in high-elevation regions, regular can mean less than 87, owing to the difference in fuel/air the thinner atmosphere causes.
Now, as we all know, the higher the Octane, the more knock resistant the gas. But some people think that the more expensive stuff also makes more power, like it has more BTUs in it or something. Of course, that’s not really the case, but that’s what I’ve heard people say.
Some manufacturers require premium fuel in certain of their cars due to a high compression ratio or ECU settings. Others specifically say in the owner’s manual that anything higher than regular is of no value and might actually damage the engine. These days the electronic engine controls typically mean that even if 91 is mandated, you can do a tank of regular in a pinch without much issue, although there was that Caddy that was killed by regular a month or so ago.
So what does your car maker recommend for your steed? If it’s anything more than 87, do you always abide as the Dude says you should? Also what’s the minimum octane in your area, are you getting all your Stones-answering RON? What’s your Octane of choice?
Image sources: [Lion’s Gate Publicity, Wikipedia]

48 Comments

  1. The LS2 in the GTO is downright evil when it comes to pulling timing on anything less than premium. It's worth the couple of extra bucks at fill up time for me.

  2. 87 in the Jeep
    89 in the Falcon (low compression motor)
    91 in the Country Sedan, WRX and Uberbird

      1. High comp (Country Sedan is 10.5:1) = premium. A performance turbo motor like the WRX has the ignition and fuel injection built around getting 91 (or higher), and it gets really unhappy when you don't feed it premium.
        Pretty much anything non-performance that's post 2000 or so will just retard the timing if you feed it crappier gas. Retarded timing (what?) equals less power and potentially less mileage. Hence, put in what the manual tells you to put in.

  3. Good ol' 85 octane in high-elevation Colorado. Low-compression engines will run on significantly less octane: I used to run my lawnmower and minibike off of Coleman white gas, which is probably about 80 octane. They actually ran better since there's no alcohol added.

  4. 87 all the way. The Town Cow would probably run fine on Vitalis hair tonic (It does have the secret ingredient "V7," which is probably a lot like octane booster.)

  5. i put 87 in everything i have ever owned… and they don't seem to run any worse than expected… they drive. they burn gas… good enough…
    only vehicle that ever got special treatment was the 4.6L Tbird while at the drag strip… always ran the alternate fuel tank i had installed with 100 octane fuel…. not sure if it was the lack of fuel weight or the extra octane… but the thundercock was always happy enough to run low 12s… and that made me happy (and made me money……)

  6. Family's 4-cyl Honda gets 87 here in Southern Ontario (don't think that's high elevation; we're just more north). Runs fine, really quiet car.
    Just a question for turbo owners; your cars usually run with lower compression than NA cars, right? If so, do you have the option to use lower octane gas for around-town driving? I'm thinking, for example, the 2-litre f20c honda s2000 would require premium at all times since it has a high compression ratio, but compared to, lets say, a 2-litre ej20t from an STi with lower compression(due to turbo), would the STi be able to run with the regular as long as the turbo doesn't spool? Or is it more complex than that?

    1. My mother's 1.8 Turbo New Beetle (five-speed manual, later AWV revision) usually gets fed 87. She's not a fast driver at all, though – leaves it in fifth above 35 or so, et cetera.
      It was getting high 20s for MPG, mixed driving, over the winter; it brushes 30 in the summer and has seen 36 on the freeway.

      1. Using my limited experience, I know it is more complicated than that, since a turbo engine runs at negative pressure when the turbo is not spooling. However, knowing the AWW engine as a previous owner, I know that even if it is using too low of octane, the knocks will be detected and the car will retard (or is it advance?) the timing to compensate. I don't think you will be killing the car, but you are driving it at sub optimal conditions, which may actually result in poorer gas mileage; i.e. it may be cheaper gas but you may be using more of it. She should try using 91 for a few months then compare the cost to see which one is actually cheaper.

        1. Agreed – that's how it appears to me. We've had no knocking or pinging, and only one bad tank of gas. If it were my car I'd put 91/93 in for a couple months and compare, but if it were my car I wouldn't be getting 30 MPG on regular because I have a heavier foot…

  7. Chipped the F150 and it runs great on 87, though I did notice a slight difference when I accidentally filled the tank with 92.
    Wife's Impreza gets 87.

  8. 2001 Outback H-6: 89 (91 when found cheap)
    1999 Legacy GT: 89 (91 when found cheap)
    1972 Mercedes 250: 87 or the lowest attainable octane…because burning higher octane requires that there still be some compression in the motor.

  9. Weird, we just have bad gas or really bad gas here. Anyway, I always use Shell V-Power (95 or 98, IDK) or Petrobras Podium – 95.

  10. Reagan-era, 9.8:1, naturally aspirated, tractor engine.
    What do you think I feed her?
    (As far as I know, she's never seen anything other than 87, and won't unless/until I turbocharge her.)

  11. The 02 Max demands 91 (Highest around here) and even then will ping at certain RPMs. Although I do think this may have been a problem with the car since it was built since when I had the base timing modified it was at 13 BTDC (Stock is 15 BTDC).
    The 93 Bronco pretty much will set fire to anything flammable that makes it into the tank. So far the worst was the 5 gallons of 4 year old 2-stroke I threw into the tank. The old beast happily burnt it without even a puff of smoke. One of these days I'll get ballsy enough to see how she'll run on Jack Daniels..

  12. I run what I am instructed to run by the operations manual: 91 octane.
    I have often thought of switching to E85, and I wonder if I could optimize that without any compression changes by simply increasing boost pressure, and getting the chip remapped, injectors, etc. Thus we get to the question I have not done the actual homework on: what is E85s effective octane? I know the test comes out like 105 or something, but I have heard practical application is closer to 96. Someone here I'm sure has the scientific explanation (perhaps a mad one?). The whole point is probably moot since my car is full of 23 y.o. rubber bits and seals which are already half dust, and I can't find any E85 in LA anyways.

  13. Both of our Passat V6s knock slightly with 87, so I'm sticking with the recommended premium (in the Southeast, that's 93). Not particularly powerful, but high compression.

  14. I run 87 in the Element, 93 in the Speed3 and good ole' diesel in the 335d, per manual (and logical) instruction. One of the bugs runs 108 and everyone else runs 87 or 89.

      1. Actually forgot about that damn car when making the mental list. She takes 93 as well. It may be a Toyota engine, but it's a mean one. And yes, all acceleration IS intended.

  15. The Mustang gets 100LL avgas. It only needs 87 auto fuel, but I think she deserves better. Mrs. engineerd's Escape has the V6, which thank God is not the FlexFuel engine. Otherwise, it would want some of my beloved scotch.

  16. The Legacy GT requires 91 or 92, the Alfa gets regular unleaded and the Dodge runs on whatever nasty brew I drain from the tanks of decrepit project cars and old lawnmowers.
    Seriously, I have discovered that QT's is the only regular octane fuel that will make the Ram detonate like a brick of lady fingers.

    1. I've got a Legacy GT as well, and for a while it griped if I fed it anything less than 91. I replaced a faulty knock sensor and now it's perfectly content on 89.

      1. I've heard a couple of horror stories about multiple knock sensor failures from folks who were determined to run on mid-grade.
        I like to put my foot in, so I haven't tested the lower limits of octane in the 8 months or so that I've had the car. Another run up in prices may have me reconsidering.

  17. 91 required. My ECU was tuned on 91 and (because of the reflash/tune) will no longer retard timing based on the knock sensor, so if I feed Ol' Grumpy anything but CA's finest pisswater he gets mad.

  18. When I had a gas car, 87. Now that I drive a diesel, the stations around here don't offer premium diesel with a higher cetane, so I just take the pump that's not gasoline or kerosene.

  19. Daily drivers, TrailBlazer takes 87 octane, Impala 87 octane or E85 when the gas goes to high and the price offset/mileage loss works in our favor.
    Bimmers and Apache get 87 octane.
    Edsel now will get 87 octane since we switched the heads to run unleaded.
    Camaro runs 93 octane plus a octane boost sometimes. Sometimes it runs E85. I only have one station near for E85 but it is close so the switch over was a no brainer. I was paying somewhere around $2.50 for E85 last summer when 93 plus octane boost put me in the $4.50 range, maybe more depending on the price of the octane boost. If I mapped the fuel to just straight 93 octane the car didn't have as much get up and go. With the E85 I have more advance mapped in and the injectors opening up a tad more. My power increases, the engine runs a few degrees cooler and the mpg doesn't change. Hard to change from 10mpg…if I keep my foot out of it….

    1. Edsel? You've got an Edsel? Which one? There's a guy down the hill from me in "The Village" (La Jolla) who has four of them in front of his house. Whenever I drive by, I don't care what my mood is, they make me smile.

  20. The Accent hasn't earned anything better than 87, and doesn't need it. Most of my cars have needed nothing else. My Intrepid would run alright on 87 (a little rough, and fuel economy was worse than usual), but after a few months I just switched back to 89.

  21. I put 94 in my Austin that has 8:1 compression.. it has the notoriously soft head A series engine, on the plus side it seems to sip gas, but burns/leaks oil, so I guess it balances out in the end….

  22. Random ranting follows:
    Around here (Fargo) you can get 87, 89 and 91. If you need more than 91, better live close to a racetrack because you're going to have a heck of a time finding it.
    My area states have some interesting quirks:
    -In ND you never know whether 87 or 89 will be the ethanol blend, and sometimes the blends trend in a seemingly backwards pattern (i.e. 87 is 10%, but 89 is 5%.)
    -In SD you'll often find that 89 with 10% ethanol is cheaper than 87 without any corn squeezin's.
    -In MN there are 91 octane pumps almost everywhere, but most are with big scary stickers reading "NONOXYGENATED GASOLINE. FOR USE IN COLLECTOR VEHICLES OR VEHICLES ELIGIBLE TO BE LICENSED AS COLLECTOR VEHICLES, OFF-ROAD VEHICLES, MOTORCYCLES, BOATS, SNOWMOBILES, OR SMALL ENGINES ONLY" and "collector vehicle" defined as "a motor vehicle for which the commissioner of public safety has issued a pioneer license, classic car license, collector license, or street rod license under section 168.10, or a motor vehicle registered as a collector vehicle in another state." (Got a 91-octane-needing car built in the last 20 years? Technically, you're screwed.)
    Now on to the cars:
    Thunderbird: 87 is required, I'll run 89 in summer if I hear any ping.
    Dakota: 87 required.
    In both the 4-wheelers, ethanol doesn't seem to affect them. I'll use the ethanol handle in winter (beats messing with gas line antifreeze any day) but otherwise I just go for the cheaper option with a preference for 87.
    As for the KLR650…
    The thing hates ethanol. The lawmakers who want to mandate blends beyond 10% can kiss my shiny metal FMF silencer, it likes unadulterated 87 best and sometimes has performance issues on 10% blend 87. Interestingly it runs even worse on the aforementioned MN 91 octane if ambient temperature is too low.

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