89 or 93 pump gas
07-26-2013 | 04:50 PM
#13
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From: central NY
Might wanna post the model no. of the GM grate you bought or better yet a link to a/the site for the same engine. Do that and maybe one of the more knowlegible members will see what you really have and chime in, if you don't piss them off....
FWIW I ran the snot out of a ZZ502/502 for 4 seasons and used either 91 or 93 octane. ZZ502 had 9.6:1 compression and aluminum heads. You have (you say) 8.75 comp. Doesn't seem you'd need to run 92, but I would if GM recommends it.
FWIW I ran the snot out of a ZZ502/502 for 4 seasons and used either 91 or 93 octane. ZZ502 had 9.6:1 compression and aluminum heads. You have (you say) 8.75 comp. Doesn't seem you'd need to run 92, but I would if GM recommends it.
07-26-2013 | 05:45 PM
#14
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Joined: Sep 2001
Posts: 5,769
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From: tn
lol. he must have really been a turd to you MT. I hate that I missed that.
The OP is clearly weighing the odds to save on fuel costs. I don't blame him - most marinas around here charge a huge premium for 93. Bottom line is, if you need the octane, you better use it. If you don't need the octane, it's a waste of money. Octane slowly "degrades" through evaporation of the anti-knock volatiles, so if your boat sits for a long time the octane will drop a bit. Keep that in mind if you do choose lower octane fuel for the busy season.
There's no magic required here to know whether your motor needs extra octane or not. If it will run under load at all speeds in hot weather without pinging (either audibly or as evidenced on the plugs) then you don't need additional octane. Additional octane gives a larger buffer zone to work within, but then again, there is zero reason to run 93 in a motor that is happy on 87. It won't run "better", it will make "less" power (although not enough difference to be likely for you to feel), and it will be a TINY bit harder to start (although modern coils pack enough punch to light off whatever you want to pour in) when you run higher octane than you actually require. The one and only benefit you get is that you get a larger buffer between where you are and ping-town.
Don't get me wrong, detonation will kill your motor if not kept in check - but if you're not getting detonation, then there is no reason to add octane unless you want a bigger buffer or plan to store the boat for a longer period (but Sta-Bil is your friend, then - or race gas...).
MC
07-26-2013 | 07:16 PM
#16
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From: yorkville,il
07-27-2013 | 12:19 AM
#17
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Joined: Oct 2004
Posts: 620
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From: Cincinnati, Ohio
Might wanna post the model no. of the GM grate you bought or better yet a link to a/the site for the same engine. Do that and maybe one of the more knowlegible members will see what you really have and chime in, if you don't piss them off....
FWIW I ran the snot out of a ZZ502/502 for 4 seasons and used either 91 or 93 octane. ZZ502 had 9.6:1 compression and aluminum heads. You have (you say) 8.75 comp. Doesn't seem you'd need to run 92, but I would if GM recommends it.
FWIW I ran the snot out of a ZZ502/502 for 4 seasons and used either 91 or 93 octane. ZZ502 had 9.6:1 compression and aluminum heads. You have (you say) 8.75 comp. Doesn't seem you'd need to run 92, but I would if GM recommends it.
Thanks for your thoughts on the matter..
07-27-2013 | 12:27 AM
#18
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From: Cincinnati, Ohio
lol. he must have really been a turd to you MT. I hate that I missed that.
The OP is clearly weighing the odds to save on fuel costs. I don't blame him - most marinas around here charge a huge premium for 93. Bottom line is, if you need the octane, you better use it. If you don't need the octane, it's a waste of money. Octane slowly "degrades" through evaporation of the anti-knock volatiles, so if your boat sits for a long time the octane will drop a bit. Keep that in mind if you do choose lower octane fuel for the busy season.
There's no magic required here to know whether your motor needs extra octane or not. If it will run under load at all speeds in hot weather without pinging (either audibly or as evidenced on the plugs) then you don't need additional octane. Additional octane gives a larger buffer zone to work within, but then again, there is zero reason to run 93 in a motor that is happy on 87. It won't run "better", it will make "less" power (although not enough difference to be likely for you to feel), and it will be a TINY bit harder to start (although modern coils pack enough punch to light off whatever you want to pour in) when you run higher octane than you actually require. The one and only benefit you get is that you get a larger buffer between where you are and ping-town.
Don't get me wrong, detonation will kill your motor if not kept in check - but if you're not getting detonation, then there is no reason to add octane unless you want a bigger buffer or plan to store the boat for a longer period (but Sta-Bil is your friend, then - or race gas...).
MC
The OP is clearly weighing the odds to save on fuel costs. I don't blame him - most marinas around here charge a huge premium for 93. Bottom line is, if you need the octane, you better use it. If you don't need the octane, it's a waste of money. Octane slowly "degrades" through evaporation of the anti-knock volatiles, so if your boat sits for a long time the octane will drop a bit. Keep that in mind if you do choose lower octane fuel for the busy season.
There's no magic required here to know whether your motor needs extra octane or not. If it will run under load at all speeds in hot weather without pinging (either audibly or as evidenced on the plugs) then you don't need additional octane. Additional octane gives a larger buffer zone to work within, but then again, there is zero reason to run 93 in a motor that is happy on 87. It won't run "better", it will make "less" power (although not enough difference to be likely for you to feel), and it will be a TINY bit harder to start (although modern coils pack enough punch to light off whatever you want to pour in) when you run higher octane than you actually require. The one and only benefit you get is that you get a larger buffer between where you are and ping-town.
Don't get me wrong, detonation will kill your motor if not kept in check - but if you're not getting detonation, then there is no reason to add octane unless you want a bigger buffer or plan to store the boat for a longer period (but Sta-Bil is your friend, then - or race gas...).
MC
It really isn't about money, I more than likely will keep running the better gas.. I was just curious why there saying to run higher octane in a 8.75 compression engine..
07-27-2013 | 12:31 AM
#19
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From: Cincinnati, Ohio
Chances are, you can probably run 87 octane.
But you'll have to test it yourself.
If you have a good ear, you can listen for pinging and if you hear any then it's clearly not enough octane for your setup (although changing your ignition curve may give you enough leeway to run it).
If you don't HEAR pinging, then make a few runs, make a wide open run and then check the plugs - you'll be looking for any signs of little metallic dots, which are a sign of detonation.
Hot weather will lower the detonation threshold, so test during HOT weather.
If your tests do not reveal any detonation evidence on the plugs, and you can't hear any detonation, then run the cheap stuff.
But occasionally pull a plug and check if you do.
MC
But you'll have to test it yourself.
If you have a good ear, you can listen for pinging and if you hear any then it's clearly not enough octane for your setup (although changing your ignition curve may give you enough leeway to run it).
If you don't HEAR pinging, then make a few runs, make a wide open run and then check the plugs - you'll be looking for any signs of little metallic dots, which are a sign of detonation.
Hot weather will lower the detonation threshold, so test during HOT weather.
If your tests do not reveal any detonation evidence on the plugs, and you can't hear any detonation, then run the cheap stuff.
But occasionally pull a plug and check if you do.
MC
