kfennell Posted May 13, 2015 Share Posted May 13, 2015 We have a community gas tank here that only has 87 octane in it, I am exploring all my options, and would maybe consider a new 6.2L mastercraft, but the manual says the following: The Ilmor MV8 engine (5.7L, 6.0L, 6.2L and 7.4L) requires a minimum of 87 octane fuel. The octane number is based on the pump octane number, which is (R + M)/2, where R is the research octane number and M is the motored octane number. For better performance, 93 octane fuel is recommended. I am imagining it retards the timing a little on 87 and so the power is down a bit, but I guess it will still be plenty starting with 445HP. Thoughts? Link to comment Share on other sites More sharing options...
Baller Jordan Posted May 13, 2015 Baller Share Posted May 13, 2015 I wouldn't be too worried about the power, but here in Ontario the lower octane gasolines include more ethanol.... We can get ethanol free gas here if we pay up for "premium" Link to comment Share on other sites More sharing options...
Baller_ The_MS Posted May 13, 2015 Baller_ Share Posted May 13, 2015 We can get non oxygenated 91 here in MN but not 93. Link to comment Share on other sites More sharing options...
kfennell Posted May 13, 2015 Author Share Posted May 13, 2015 @Jordan No such thing here. Almost all gas has ethanol in it, and no way to get ethanol free delivered. Link to comment Share on other sites More sharing options...
Baller MattP Posted May 13, 2015 Baller Share Posted May 13, 2015 @kfennell you are in oil country and can't get ethanol free delivered? Link to comment Share on other sites More sharing options...
kfennell Posted May 13, 2015 Author Share Posted May 13, 2015 Indeed Link to comment Share on other sites More sharing options...
Baller oldjeep Posted May 13, 2015 Baller Share Posted May 13, 2015 Who cares about non ethanol, can't you get a higher octane e10? Seems silly to buy a high performance engine and not be able to use all the power you paid for. Link to comment Share on other sites More sharing options...
kfennell Posted May 13, 2015 Author Share Posted May 13, 2015 It is possible, but the majority of people only use 87 and only the Ilmors actually suggest using higher, so there would be most of the lake paying more for gas they don't want or need. I can get gas from the station, but using 5G jugs is a pain!!! Link to comment Share on other sites More sharing options...
Baller oldjeep Posted May 13, 2015 Baller Share Posted May 13, 2015 Illmor isn't the only one. Indmar says 89 for all but the lsa and ls3 which need 91 (2012 manual) no 87 allowed. How old are the rest of the boats on the lake? Link to comment Share on other sites More sharing options...
kfennell Posted May 13, 2015 Author Share Posted May 13, 2015 Almost all brand new, but I guess they are 75% PCM 343 and the rest of the Indmar owners don't seem to know or care that it calls for 89 because they are all running 87. I am suprised to read that, I just assumed that since everyone was running 87 it was OK with them! Link to comment Share on other sites More sharing options...
Baller 6balls Posted May 13, 2015 Baller Share Posted May 13, 2015 I run 87 octane in a 500 plus hp 6.3 liter AMG V8 with a difference in HP I don't notice from premium. My 225 hp yamaha EFI also calls for premium...it's now ancient and runs great on 87 it's entire life. I wouldn't waste the dough on premium...and you won't be disappointed in the getty up of the 6.2 Prostar...super strong. Link to comment Share on other sites More sharing options...
fox197 Posted May 14, 2015 Share Posted May 14, 2015 Not sure if Australia measures there octane rating differently but i use 98 octane in my 6.0l ilmor. Link to comment Share on other sites More sharing options...
Baller oldjeep Posted May 14, 2015 Baller Share Posted May 14, 2015 In Australia you use the RON rating, here in the US we use (RON+MON)/2. So your ratings for the same fuel will show about 4-6 points higher. Your fuel would be approx 92-94 octane here. Link to comment Share on other sites More sharing options...
Baller_ MISkier Posted May 14, 2015 Baller_ Share Posted May 14, 2015 Unless I could not get 89 octane at the gas station or marina, I have always used 89 in my Indmar engines. I hate that we are stuck with ethanol. I can occasionally find a station that sells ethanol-free "recreational fuel", but it is very rare. The worst slalom equipment I own is between my ears. Link to comment Share on other sites More sharing options...
Baller oldjeep Posted May 14, 2015 Baller Share Posted May 14, 2015 Mine always runs on 89 E10 - or 91 if we are in one of those states with no ethanol and no 89 ;) I figure if the mfg of my $8000 engine says I should run 89 then I'll do that. Sounds like Ilmor has engine maps that can compensate all the way down to 87 octane. My truck is like that - will run on 87 but 89 is recommended and on that I can tell the difference between the 2. Link to comment Share on other sites More sharing options...
Baller Razorskier1 Posted May 14, 2015 Baller Share Posted May 14, 2015 I run mu 6.2L Ilmoor on whatever my wife brings home in the gas cans. She's pretty cheap, so I'm sure it is 87 octane. When I fill the cans I usually do premium, but that's by far the minority of the time. As for ethanol, I run gas with ethanol because it is closer to home to buy it. And since I burn through gas pretty fast, I'm not worried about it sitting too long. There are places that sell 91 non-ox. Link to comment Share on other sites More sharing options...
Baller m_pags Posted May 15, 2015 Baller Share Posted May 15, 2015 @Razorskier1 you've got it made if your wife is filling the gas cans for the boat. Does she dump them in too? :) Link to comment Share on other sites More sharing options...
Baller LeonL Posted May 15, 2015 Baller Share Posted May 15, 2015 How about octane boosters like Lucas? Do,they work? Worth researching I'd say, if you have a real concern. Link to comment Share on other sites More sharing options...
Baller Razorskier1 Posted May 15, 2015 Baller Share Posted May 15, 2015 @m_pags I do all the carrying to the dock and pouring, but I am fortunate that my wife fills six gas cans a week all summer without complaining! Link to comment Share on other sites More sharing options...
Baller Kelvin Posted May 15, 2015 Baller Share Posted May 15, 2015 If your switching between different octane levels, you likely aren't getting the benefits of the higher octane as it takes awhile for the ECM to adjust the timing for the higher octane. At the Malibu Open one year, Dennis Kelly was resetting the history on the ECMs for some of the boats that had been running 87 octane. They were running the recommended fuel at the Open to get maximum performance. Link to comment Share on other sites More sharing options...
Baller eleeski Posted May 15, 2015 Baller Share Posted May 15, 2015 I used to run 87 octane cargas in my Cessna 182. It had more power with the 87 octane than with 100 octane low lead avgas. The engine did run a bit hotter but still within limits. The increased performance was very apparent in the climb rate and fuel burn which need to be carefully monitored when flying. So now I always choose the lowest octane fuel I can find - to get the best performance. Eric Link to comment Share on other sites More sharing options...
FracBurner Posted May 15, 2015 Share Posted May 15, 2015 Engines don't "know" what octane is being run. They do know if knock is present and retard ignition momentarily to cool the cylinder. The ignition adjustment is practically instantaneous. Once the load is reduced, optimal timing is restored because the temp falls and no knock is detected. Run 87 and be happy. If you plan to use your boat as a low speed tug boat requiring sustained full throttle operation, go for the 93. Link to comment Share on other sites More sharing options...
Baller Deke Posted May 18, 2015 Baller Share Posted May 18, 2015 @eleeski I use my boat at 6900' and was told early on not to bother with premium gas. There is apparently not enough oxygen to use the extra octane, so why bother. Maybe this is same with your airplane? Link to comment Share on other sites More sharing options...
Baller eleeski Posted May 18, 2015 Baller Share Posted May 18, 2015 @Deke My airplane has mixture control. The fuel air mix is controlled and monitored by the pilot. Altitude is compensated for as the plane climbs. Not quite the same as fuel differences are noticeable. Practically, you are correct. Mechanics told me not to worry about getting settings perfect above 6000 feet because the engine couldn't make over 75% power so I couldn't overload the engine regardless. Overheating was always a concern and 87 octane fuel required a bit different settings than 100 octane. Of course many departures were from below sea level on cold days where the air was extremely dense. Fuel needs to perform there most critically. Note that the engine was designed for 87 octane leaded fuel. Neither 100 octane low lead nor 87 octane unleaded fuel was "right" for the engine. But those were the choices available. Eric Link to comment Share on other sites More sharing options...
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