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Author Topic:   Gas octane 87 vs 93

striper swiper posted 07-28-2009 09:45 AM ET (US)
I have a 89 johnson 150 hp on my boat.
The 1989 manual says to use 87 octane, but I don't think the gas they recommend is formulated the same way especially with ethanol being forced down our tanks.
Is 93 octane a better choice over the 87?
Cost really isn't much of a factor ,I think we would all pay more for better performance.
Tom W Clark posted 07-28-2009 09:48 AM ET (US)
There will be zero improvement in performance when using 93 octane gasoline in that motor. No benefit whatsoever.
gnr posted 07-28-2009 10:24 AM ET (US)
In fact, it may degrade performance a tad if your 20 year old ignition system has lost a half step.
Tohsgib posted 07-28-2009 11:03 AM ET (US)
The only benefit(these days) to running 93 is that new gas deteriorates after 30 days or so. If you run 87 and don't use it up quickly it may be only 85 in a few weeks. This can cause detonation and engine failure. Your manual says that your engine needs 87 MINIMUM. If you run 89 or 93 at least your window of opportunity is longer with older fuel.
Tom W Clark posted 07-28-2009 11:32 AM ET (US)
Nick,
What is the octane of 87 that has been sitting for a year and a half?
R T M posted 07-28-2009 12:19 PM ET (US)
Has a study ever been done on this? I`ve used 6 month old gas in my 08 25 Merc 4 stroke with no problems, but I did notice the fuel turns from almost clear to a slight amber color.
rich/Binkie
PeteB88 posted 07-28-2009 01:57 PM ET (US)
Know it all relative who wrenches on everything, grew up with wrenches and Lincoln welders instead of toys insisted I put premium 92 octane in my Yamaha 40 (92) and all my 2 stroke engines. Dang near threw a fit about it. I put tank after tank in that Yamaha ignoring the manual. Then I filled up with 87 and that motor ran perfectly. Complete change. Same with oil - Yamalube made significant difference.
striper swiper posted 07-28-2009 02:36 PM ET (US)
Thanks for the info. 87 it is.now do you leave the tank full or empty at season end?
Tohsgib posted 07-28-2009 03:14 PM ET (US)
Tom it really depends on the grade of fuel. I have seen gas getting stale after 3 weeks in the FL sun. Years back have run engines with 10 year old gas. Stabil, etc have a lot to do with it as well. The fuel I use at my marina is Valvetech and it has stabil & seafoam like stuff and no ethanol and is 89 octane. It is like $.30 more a gallon but if I added a bottle of Seafoam, Valvetech, startron, etc to my tank it would cost more than $.30 a gallon.
If you know you are gonna burn it up within a few weeks, buy 87. I am never sure so I always buy 89 which by the way is what all the marinas by me sell. Same reason I would not want a 275 or 300 Verado, I can't find Super on the water down by me.
modenacart posted 07-28-2009 08:37 PM ET (US)
most of the gas stations get their gas from the same place. Its just the additives at the pump that are different.
number9 posted 07-29-2009 05:24 AM ET (US)
A couple of descriptions of how ethanol and additives are blended into gasoline prior to station delivery.
After shipment through the pipeline, gasoline is typically held in bulk storage terminals that often service many companies. At these terminals, the gasoline is loaded into tanker trucks destined for various retail gas stations. The tanks in these trucks, which can typically hold up to 10,000 gallons, usually have several compartments, enabling them to transport different grades of gasoline or petroleum products. The truck tank is where the special additive packages of gasoline retailers get blended into the gasoline to differentiate one blend from another. In some areas, ethanol may be “splash blended” in the tanker to meet environmental requirements. When the tanker truck reaches a gas station, the truck operator unloads each grade of gasoline into the appropriate underground tanks at the station.
************************************************************
Instead of purchasing ethanol and gasoline already blended at a wholesale terminal, a distributor or retailer buys them separately. The ethanol is then splashed into the gasoline either in the tanker truck or sometimes in the storage tank of a retail station.
If it isn't mixed well, splash-blended fuel sometimes stratify into layers of ethanol and gasoline in storage tanks, Curran said. That means that even if there's only 10 percent ethanol in its tank, a retail station could pump more than that into your car.
Even the distance the tanker-truck has to travel to make a delivery can make a difference. Splash blending is often called "stoplight blending" because at least some of the mixing takes place by the fuel sloshing around when the tanker-truck comes to a stop.
dino54904 posted 07-29-2009 11:20 AM ET (US)
I always use 93 because at most filling stations in my area they don't put ethynol into the Super Grade gasoline. I figure the extra price is worth not having ethynol in the tank and through the engine.

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Author	Topic: Gas octane 87 vs 93
striper swiper	posted 07-28-2009 09:45 AM ET (US) I have a 89 johnson 150 hp on my boat. The 1989 manual says to use 87 octane, but I don't think the gas they recommend is formulated the same way especially with ethanol being forced down our tanks. Is 93 octane a better choice over the 87? Cost really isn't much of a factor ,I think we would all pay more for better performance.
Tom W Clark	posted 07-28-2009 09:48 AM ET (US) There will be zero improvement in performance when using 93 octane gasoline in that motor. No benefit whatsoever.
gnr	posted 07-28-2009 10:24 AM ET (US) In fact, it may degrade performance a tad if your 20 year old ignition system has lost a half step.
Tohsgib	posted 07-28-2009 11:03 AM ET (US) The only benefit(these days) to running 93 is that new gas deteriorates after 30 days or so. If you run 87 and don't use it up quickly it may be only 85 in a few weeks. This can cause detonation and engine failure. Your manual says that your engine needs 87 MINIMUM. If you run 89 or 93 at least your window of opportunity is longer with older fuel.
Tom W Clark	posted 07-28-2009 11:32 AM ET (US) Nick, What is the octane of 87 that has been sitting for a year and a half?
R T M	posted 07-28-2009 12:19 PM ET (US) Has a study ever been done on this? I`ve used 6 month old gas in my 08 25 Merc 4 stroke with no problems, but I did notice the fuel turns from almost clear to a slight amber color. rich/Binkie
PeteB88	posted 07-28-2009 01:57 PM ET (US) Know it all relative who wrenches on everything, grew up with wrenches and Lincoln welders instead of toys insisted I put premium 92 octane in my Yamaha 40 (92) and all my 2 stroke engines. Dang near threw a fit about it. I put tank after tank in that Yamaha ignoring the manual. Then I filled up with 87 and that motor ran perfectly. Complete change. Same with oil - Yamalube made significant difference.
striper swiper	posted 07-28-2009 02:36 PM ET (US) Thanks for the info. 87 it is.now do you leave the tank full or empty at season end?
Tohsgib	posted 07-28-2009 03:14 PM ET (US) Tom it really depends on the grade of fuel. I have seen gas getting stale after 3 weeks in the FL sun. Years back have run engines with 10 year old gas. Stabil, etc have a lot to do with it as well. The fuel I use at my marina is Valvetech and it has stabil & seafoam like stuff and no ethanol and is 89 octane. It is like $.30 more a gallon but if I added a bottle of Seafoam, Valvetech, startron, etc to my tank it would cost more than $.30 a gallon. If you know you are gonna burn it up within a few weeks, buy 87. I am never sure so I always buy 89 which by the way is what all the marinas by me sell. Same reason I would not want a 275 or 300 Verado, I can't find Super on the water down by me.
modenacart	posted 07-28-2009 08:37 PM ET (US) most of the gas stations get their gas from the same place. Its just the additives at the pump that are different.
number9	posted 07-29-2009 05:24 AM ET (US) A couple of descriptions of how ethanol and additives are blended into gasoline prior to station delivery. After shipment through the pipeline, gasoline is typically held in bulk storage terminals that often service many companies. At these terminals, the gasoline is loaded into tanker trucks destined for various retail gas stations. The tanks in these trucks, which can typically hold up to 10,000 gallons, usually have several compartments, enabling them to transport different grades of gasoline or petroleum products. The truck tank is where the special additive packages of gasoline retailers get blended into the gasoline to differentiate one blend from another. In some areas, ethanol may be “splash blended” in the tanker to meet environmental requirements. When the tanker truck reaches a gas station, the truck operator unloads each grade of gasoline into the appropriate underground tanks at the station. ************************************************************ Instead of purchasing ethanol and gasoline already blended at a wholesale terminal, a distributor or retailer buys them separately. The ethanol is then splashed into the gasoline either in the tanker truck or sometimes in the storage tank of a retail station. If it isn't mixed well, splash-blended fuel sometimes stratify into layers of ethanol and gasoline in storage tanks, Curran said. That means that even if there's only 10 percent ethanol in its tank, a retail station could pump more than that into your car. Even the distance the tanker-truck has to travel to make a delivery can make a difference. Splash blending is often called "stoplight blending" because at least some of the mixing takes place by the fuel sloshing around when the tanker-truck comes to a stop.
dino54904	posted 07-29-2009 11:20 AM ET (US) I always use 93 because at most filling stations in my area they don't put ethynol into the Super Grade gasoline. I figure the extra price is worth not having ethynol in the tank and through the engine.