Fuel type? 87, 89, 91 octane?

[Fman]

What is everyone running in there boats? I believe the CAT ETX Indmar is calling for 89, does this really make a difference? I have used 87/89 both and never noticed any difference. I also heard running 91 can do more harm than good if it is calling for 89?

Anyone?

Fuekl is spelled incorrectly, should be fuel....woops.

[michael hunter]

At the price of gas these days I run 87 regular in both my 89 351 and 08 350 cat.

[Skylar18]

Running 89 or 91 depending on where I am on the lake when I need to fill up. Don't notice a difference between the 2.

[riveredge]

Modern EFI engines can adapt to 87, 89, 91, 93, whatever you feed them. There is no doubt an optimum fuel they're designed to run on, but the computer will adapt, so don't worry about it. If you fill up at gas stations, pay the extra couple pennies for the right fuel. On a lake like mine where there are only a few places to fuel up and they all carry 87, well, that's what you get, and your engine will survive just fine.

[KG's Supra24]

89 is what I try to run. If it's between 87 or 91, like on my lake, I go 91.

[natemclain]

The marina where I keep my boat has 91.
Seems to work the same as it did when I was filling up before going to the lake in the past.

Nate

[saltare inverts]

My last boat with 351 pcm didnt like 87 octane. It wanted to ping and knock. When I used good octane booster(much cheaper as mentioned in earlier post) knock was gone. My Saltair now doesnt matter. I do watch were I buy gas. Some place will use very cheap low octane fuel. All Caseys general stores do and alot of mom and pop stores. I try to always use phillips 66 or qt etc.

[Fman]

Thanks for all the feedback, will be sticking with 89 when possible... its only about $4-$5 difference per fill up from the 87.

[KG's Supra24]

Agreed, the difference isnt that much. I'd just fill up at popular places, like mentioned above. Places with alot of turnover where the gas is fresh.

[ScottnAz]

Agree with KG, fresh gas is probably the most important factor no matter which octane is choosen.
Right or wrong, I've been running 89+ as suggested in my manual.

[KG's Supra24]

Along the same topic ...

Do you fill the tank up when you put the boat away for the week? I have heard it is best to put the boat up with a full tank but i dont know what the benefit is. I have started doing this but simply because of one thread i read (maybe on wakeworld). Am i supposed to be doing this?

[ScottnAz]

I always store the boat full of gas. It's my understanding this limits the possibility of water condensation in the tank.
If the boat is stored and unused for more than 6 weeks, I add a fuel treatment to the tank before taking the boat out.

[JohnnyH]

I use 93 octane. If you can afford this kind of boat you should be able to afford the best fuel. The added expense is like what? A beer at the bar?? FYI, If you leave fuel in your tank for more than 2 wks the octane falls. So if your boat sits up for 2-3 wks that 87 octane is around 85..

[JoHNI_T]

I always store the boat full of gas. It's my understanding this limits the possibility of water condensation in the tank.
If the boat is stored and unused for more than 6 weeks, I add a fuel treatment to the tank before taking the boat out.



always store tanks full, like said above the more inside of the tank exposed allows for condensation when the tank heats and cools, if its filled to the neck there is no roon for moisture to form.

My dealer said to run regular 87 I did run 91 in my 06 5.7 325hp for 2 years then I switched to 87 and never noticed a difference, so I usually run 87 theese days,, and 87 is usually the freshest fuel.

[[email protected]]

Just bought an 89 supra and was wondering what gasoline to use? Can I fill it at a gas station/ with my tanks? Do I need to add any additives?

[NorCalPR]

87. I ran it that way in my 98 comp and sane way in my 96 brendella. Brother runs a new malibu with a 350, and he runs 87...

Unless its pinging, there is zero reason to run the 91 grade. Octane is there for pinging resistance.


You have to realize these motors were in trucks meant to run on nearly 0 octane...

Run 87 and be done with it. The rest is a waste (unless youre running some high performance motor like a 6.0 or a vette motor)

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[Sdc77]

In France we have 91, 91 +10% Ethanol (call E10) and 93.
I run E10 (91) for 4 years now without issue in the carbed 454.

[Moor]

IMO, you guys should be more concerned about running ethanol free gas in your boats over what octane rating your running. I won't get into the havoc that ethanol will wreak on your fuel system, google can tell you all about that.

If you fill up with 89 or better you shouldn't have any octane related issues. I've used 87 in my old sunsport in a pinch and didn't notice a difference. Modern fuel injected engines with electronic ignitions will retard the timing to prevent engine damage if lower than recommended octane is used. Older boats usually have lower compression engines and were designed to run on lower (89) octane.

[Southerngrounds]

100% gas NO ethanol!!! The octane rating becomes a factor on high compression motors. If you hear the motor ping or knock bump up the octane rating. It's most important to run 100% gas.

[korey]

Most of the marinas in the area and a few land based filling stations near our larger lakes (Cumberland and Dale Hollow in KY/TN) are carrying the Rec-90 (ethanol-free, 90 octane unleaded gasoline blend designed for use in recreational/marine engines). I've never believed in running any special gas in an old 10:1 compression ratio big block, but my boat LOVES this rec-90... Maybe it me subliminally justifying paying $3.89/gal on the water, but I swear the boat runs better on it!

[Moor]

Most of the marinas in the area and a few land based filling stations near our larger lakes (Cumberland and Dale Hollow in KY/TN) are carrying the Rec-90 (ethanol-free, 90 octane unleaded gasoline blend designed for use in recreational/marine engines). I've never believed in running any special gas in an old 10:1 compression ratio big block, but my boat LOVES this rec-90... Maybe it me subliminally justifying paying $3.89/gal on the water, but I swear the boat runs better on it!

Unless you changed pistons, your 454 has around 8.5:1 CR, same as mine. It will run on damn near anything lol. And no, your not crazy, All of my carburated engines run better on Non-ethanol fuel. I think the lack of Ethanol is what you notice more than the higher octane.

[NorCalPR]

Yep. No ethanol is nice because it doesnt go bad and you get more power, but is it absolutely necessary? Not for a old iron block chevy/ford...

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[cadunkle]

I've always used 89 in my PCM 454. The Supra manual doesn't mention octane requirement of any engine. PO said he rebuilt it and no idea what pistons he used so not sure if it's a 8.5-9:1 compression ratio or something more, or even if it's stock bore and pistons and was just freshening up with rings and bearings. I want to run it low and try 87 to see it it detonates at all. The spread used to be 5-10 cents between octane ratings, now it's more like 30-40 cents more for 87 and another 10-20 for 93. Extortion for those of us who built engines to run 93 specifically because the engine would be more efficient and have a lower cost per mile or hour of operation than lower compression on 87.

[Moor]

if the compression ratio is kept below about 9.25:1 then running 89 octane shouldn't cause detonation if the engine is tuned properly. Anything above that, i'd recommend at least 91 octane.

[[email protected]]

thanks everyone 87 it is!