Fuel Question

Discussion in 'General Discussion' started by Katemma Life, Apr 8, 2020.

  1. Katemma Life

    Katemma Life Member

    104
    Oct 7, 2018
    cape cod
    2007 sea ray 290 SLX
    Twin mercruiser MAG 350 MPI w/ Bravo III
    This may or may not be a reasonable question but here goes..
    My Mercruiser 350 MAG engines have a spec for (I think) 90 octane gas. Is there any harm, or is it better for the engines, to put super unleaded in them? I have the opportunity to fill up with Super - 93 octane

    thanks for your inputs!!!
     
  2. Wylie_Tunes

    Wylie_Tunes Active Member

    796
    Oct 26, 2012
    Lake Wylie NC area
    N/A
    N/A
    There is no harm to run a higher then required octane, but not recommended to run a lower then required octane. No performance advantage to higher octane as well, despite the TV commercial adds from all the major labels.
     
  3. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    Spec is actually 87 - that is all that is required. There is no real benefit to using a higher octane since the engine doesn't require it (it's not a high-compression engine) - no performance of economy benefits to be had. Now, if your gas sits for a long period of time, then there is "sort of" a benefit as gas loses it's octane as it sits. But I have NEVER seen these engines have issues due to your line of thinking, even when the boat sits for a year. BUT... it is a very good idea to use some sort of stabilizer (Startron, for example) if the gas will sit. Can't hurt anything to use it all time, either! It's pennies per gallon and gives more benefits than higher octane gas.
     
  4. Katemma Life

    Katemma Life Member

    104
    Oct 7, 2018
    cape cod
    2007 sea ray 290 SLX
    Twin mercruiser MAG 350 MPI w/ Bravo III
    Thank you Lazy Daze and Wylie!
     
  5. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    FYI... if you can find the diesel formula for Startron, you can use that. Same stuff, just more concentrated. Costs about 25% more, but goes 100% further.
     
  6. Katemma Life

    Katemma Life Member

    104
    Oct 7, 2018
    cape cod
    2007 sea ray 290 SLX
    Twin mercruiser MAG 350 MPI w/ Bravo III
    ok got it - thanks again
     
  7. sbw1

    sbw1 Well-Known Member

    Oct 10, 2006
    West Michigan
    This is listed in my signature
    This is listed in my signature
    FullSizeRender.jpg Some places sell alcohol free gasoline in their high octane grade. If that is available, you should always buy that over a non premium gasoline that has alcohol added to it. The Citgo stations in Grand Haven, for example, sell alcoholic free premium but the regular has alcohol added. There is a noticeable improvement in MPG with the premium not to mention the lack of hassles associated with alcohol. Most of the marinas sell alcohol free fuels in western Michigan. You should buy that regardless of the octane when it is available.
     
  8. KevinC

    KevinC Well-Known Member

    Feb 25, 2011
    Long Island, NY
    2004 340 Sundancer
    Twin 8.1 V-drives
    IIRC, I think Walmart sells the small bottle of Startron in store that will treat 128 gallons of gas. I think its about $10.

    -Kevin
     
  9. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    One thing to check regarding the Startron from Walmart... and this comes directly from my StarBrite (makes Startron) rep. Walmart had approached them (this was years ago, now) about wanting to sell Startron in their stores, but they wanted to be able to sell it for less than other places. The end result was an 8:1 formula where the normal formula is 16:1 (diesel is 32:1). It ended up being a dollar or two less at Walmart... but you had to use twice as much. I'm not sure if it's still that way - but be sure you're getting the 16:1 formula!

    I assume your post's intent was just to say how inexpensive this stuff is - and you're right, Kevin. I just added that extra info for "extra info" ;)
     
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  10. Katemma Life

    Katemma Life Member

    104
    Oct 7, 2018
    cape cod
    2007 sea ray 290 SLX
    Twin mercruiser MAG 350 MPI w/ Bravo III
    awesome, its great when we can get something on the cheap. I'm gonna check out walmart this week. thanks
     
  11. KevinC

    KevinC Well-Known Member

    Feb 25, 2011
    Long Island, NY
    2004 340 Sundancer
    Twin 8.1 V-drives
    Yes but there was a big cardboard tag attached that stated the total use 128 gallons and the ounces per gallon (I know this because I typically use one-half per tank on a fills ups (my tanks are 110 gals each) Are you saying that Starbrite/Startron was asked to stretch the labeling requirements for Walmart to imply an 8:1 would cover 128 gallons instead of 64 gallons?

    -Kevin
     
  12. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    Not stretch - dilute. That was the only way StarBrite was able to meet Walmart's requirements. And, of course, Walmart only really cared about the price, hoping that most of their customer's wouldn't "do the math". I'm joking a bit there - I shop there once in a while! :)

    For example, the "normal" formula for a 16oz bottle (16:1) would treat 256g, while the "Walmart Special" 16oz bottle (8:1) would only treat 128g. And the bottle was only about $2 less than buying it at a marine store. I remember actually seeing that on their shelf, too. BUT, I haven't checked in quite a while so maybe it's changed?
     
  13. Wylie_Tunes

    Wylie_Tunes Active Member

    796
    Oct 26, 2012
    Lake Wylie NC area
    N/A
    N/A
    This is actually from the absence of the ethanol and not the higher octane.
     

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