If this is your first visit, please click the Sign Up now button to begin the process of creating your account so you can begin posting on our forums! The Sign Up process will only take up about a minute of two of your time.

Follow us on Facebook Follow us on Twitter

View Poll Results: Which octane fuel do you use?

184. You may not vote on this poll
  • 87 octane (regular)

    44 23.91%
  • 89/90 octane (plus)

    27 14.67%
  • 92/93 octane (super)

    96 52.17%
  • AV/ other or Allan 4 is a putz

    17 9.24%
Page 4 of 7 FirstFirst ... 23456 ... LastLast
Results 31 to 40 of 65
  1. #31
    Registered JCPERF's Avatar
    My Boats:
    10 foot Kayak
    Join Date
    Jul 2004
    Long Island,New York

    Re: Which octane fuel do you use?

    Quote Originally Posted by Byrdman
    Do tell...what kind of motors are you running?
    Bigyellow Motors

  2. #32
    A to Z Platinum Member Sean H's Avatar
    Join Date
    Apr 2004

    Re: Which octane fuel do you use?

    Quote Originally Posted by JCPERF
    Bigyellow Motors

    with hairdryers on them......

  3. #33
    Registered wantsa311's Avatar
    My Boats:
    1995 Formula PC 34
    Join Date
    Oct 2003
    Sterling Heights, MI

    Re: Which octane fuel do you use?

    Quote Originally Posted by RollWithIt
    Use 87 octane in mine. Benefit of factory 454 mag.

  4. #34
    Banned cuda's Avatar
    Join Date
    Sep 2001
    Deland, Florida

    Re: Which octane fuel do you use?

    Quote Originally Posted by ThirdBird
    It's just amazing how many people, even supposed motor-heads, have no clue what the real function of octane is. All you need to do is read a little and get the real scoop.

    Compression, compression, compression. If you don't run a high compression engine, you don't need high octane. Octane prevents pre-ignition caused by compression. In a higher compression engine, the fuel/air may (will) explode under compression before the piston reaches the top of it's stroke. Imagine the stresses when that happens. That little "knock" you here is your piston being jammed back down on it's up-stroke. Not good! However, as many have stated above, if you don't need it, don't spend the money on it.
    I agree that high compression is the main cause of pre-ignition, but high temps will also cause it.

  5. #35
    AT Cult Member #3 VIP Member R Addiction's Avatar
    My Boats:
    '99 Active Thunder Tantrum
    Join Date
    Oct 2000

    Re: Which octane fuel do you use?

    Quote Originally Posted by Dean Ferry
    I use what Mercruiser recommends for the 502 MPIs, 87 Octane. Anything else, I'm told, is a waste of your money.
    Thats what I heard to Dean......Never had any problems

  6. #36
    Registered Clay Washington's Avatar
    My Boats:
    1990 Cigarette Bullet
    Join Date
    Dec 2000
    Austin, Texas

    Re: Which octane fuel do you use?

    I got a Whipple-charged 502. I gotta burn the good stuff!

  7. #37
    Registered DiabloFemina's Avatar
    Join Date
    Mar 2005

    Re: Which octane fuel do you use?

    Quote Originally Posted by cuda
    I agree that high compression is the main cause of pre-ignition, but high temps will also cause it.
    The primary factors for preigntion (or detonation) are intake temp, timing and fuel octane rating and compression.

    Intake temp breaks out into two factors, the ambient air temperature and the amount of charge (boost) you run. If the ambient air temperature is already 90F and you run 15 psi, then the air intake temps are gonna be through the roof. Superheated intake temps, when mixed with fuel, leave the compression mixture no "room" when compressed, the mixture is already soaked with heat, so compressing it even a small amount causes it to preignite or "detonate" (basically turns your engine into a compression ignition aka diesel engine, very bad for pistons.).

    If your engine is out of tune (timing) it will knock, or pre-ignite (this is where it becomes confusing, because pre-ignition doesn't exactly mean detonation, it just means the cylinder fires at the wrong time, which may or may not be due to detonation. If you run advanced timing, like 18 degrees plus, this means that the spark plug will spark and ignite the fuel 18 degrees BEFORE top dead center (TDC). So that the mixture ignites and pushes back on the piston at the optimal time (kinda like pushing a merry-go-round, if you wait to push the bar when it's right in front of you, it's not as effect as beggining your push slightly before it reaches you, to get the maximum effort out of it).

    Compression is the amount that the engine "compresses" the mixture (imagine that So if you have a high CR, then the fuel/air mixture will be superheated, nearly to the point of ignition. Hotter intake temperatures will obviously aggrivate this factor (heat soaking as I mentioned before).

    Lastly, like I stated earlier, engine load has a lot to do with this as well. If you have an engine in 4th gear going up hill on a 99F day with your foot to the floor, you will most likely hear that tell-tale little knocking sound (that's called engine knock or detonation), that the air/fuel mixture firing in opposition to the piston and creating massive amounts of force against the piston head and eventually, it's gonna cause a failure. Same is true of any engine, if you're in a boat and its 100F out and you're running 10psi of boost and you get on it and try to push the boat hard, it's not going to be good for your engine if you're running low ocatane fuel.

    Octane rating is a rating which averages the MON and RON (won't get into this much) Mechanical/Research Octane numbers. Basically, they are an index indicating the fuel's chemical similarity to Iso-Octane. For simplicity, you can think of this as the fuel's likelihood to pre-ignite or it's "volatility" for simplisitic purposes. A higher octane fuel resists pre-ignition.

    However, just as been shown in high end BMW's etc., if an engine is tuned to run 87 octane, that's what you should run. Running anything higher will not give you more power and actually MAY reduce power slightly (and reduce the money in your wallet in the process). In naturally aspirated engines, higher octane ratings generally equate to smoother engine operation, but not always, depending on the temps and CRs and timing (as I went through before).

  8. #38
    S.O.B (single O/B) now Platinum Member t500hps's Avatar
    Join Date
    Sep 2004
    Richmond VA

    Re: Which octane fuel do you use?

    WOW!!!! A question on OSO and consistent answers from everyone!!!! At least I'll feel comfortable running 87 from now on. Thanks for the input.
    Russ C.

  9. #39
    VIP Member VIP Member lucky strike's Avatar
    My Boats:
    Using LS-3's boat
    Join Date
    Sep 2003
    Pompano Beach, Florida

    Re: Which octane fuel do you use?

    Old Lucky Strike= 93

    New Lucky Strike= 87


  10. #40
    Registered martiniboat's Avatar
    My Boats:
    1978 Martini 25 foot and 30' 1986 Corsa ('old school is cool')
    Join Date
    Sep 2002
    Brussels, Ont. CAN. Landlocked between Lake Huron, Ontario and Erie

    Re: Which octane fuel do you use?

    87 works for me...

Page 4 of 7 FirstFirst ... 23456 ... LastLast

Similar Threads

  1. Hi-octane Fuel For L.i.
    By louietherigger in forum OPA/The Jersey Boyz
    Replies: 2
    Last Post: 08-09-2007, 09:06 PM
  2. Fuel and Octane
    By CigDaze in forum General Q & A
    Replies: 29
    Last Post: 12-20-2004, 12:21 PM
  3. What octane fuel for the motors?
    By phughes69 in forum General Q & A
    Replies: 2
    Last Post: 08-08-2004, 10:40 AM
  4. What Fuel Octane
    By Active Mike in forum General Q & A
    Replies: 28
    Last Post: 03-31-2004, 04:38 PM
  5. high octane fuel
    By Scooter in forum General Boating Discussion
    Replies: 6
    Last Post: 06-24-2002, 12:35 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
All times are GMT -5. The time now is 03:07 AM.
Powered by vBulletin® Version 4.2.0
Copyright © 2016 vBulletin Solutions, Inc. All rights reserved.
Search Engine Optimization by vBSEO 3.6.1
Original Poster In Postbit provided by Original Poster In Postbit v1.0.0 (Free) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd. Runs best on HiVelocity Hosting.
Copyright 2011 OffShoreOnly. All rights reserved.