91 Octane Fuel Issues
Thread Starter
RL Technical Advisor
Joined: May 2001
Posts: 11,870
Likes: 75
From: Portland Oregon
91 Octane Fuel Issues
Hi:
Recently, the State of California has chosen to eliminate MTBE from motor fuels and instead, use Ethanol as the oxygenate to reduce emissions.
There are some concerns about this change that everyone who drives a performance car should be aware of, especially turbocharged ones.
1) Octane Rating: The highest octane fuels you might see now are 91, instead of 92. This may be an issue for cars with certain performance chips, high compression ratios, and forced induction. 91 octane is, IMHO rather marginal unless this is taken into account when undertaking any program of performance enhancements.
I've posted a matrix chart on our website for blending 91 octane pump gas with 100 octane unleaded race gas. I hope this helps. Look at the URL below.
2) Elastomer Compatibility: This is largely an unknown as the long-term database is incomplete. For certain, Ethanol is well known to attack and slowly dissolve certain rubber parts used in all fuel systems. You may not get the long life expected from such items and this deserves some scrutiny. Ethanol is also an excellent solvent and scours out all dirt, rust, and contaminates in the fuel system sending them into the filter. This causes rapid filter clogging and immediate fuel filter changes are recommended along with more frequent changes than the Factory recommends. This will stop your car dead! Change that filter at least twice a year.
Last, octane boosters are not recommended except in emergencies. The additives in any effective octane booster leave a big brown mess inside your engine and they do not improve octane proportional to costs. Further, these additives WILL attack the rubber gaskets, O-rings and seals with the attendant troubles that this will create in the long term.
Lets Talk about Porsches
Recently, the State of California has chosen to eliminate MTBE from motor fuels and instead, use Ethanol as the oxygenate to reduce emissions.
There are some concerns about this change that everyone who drives a performance car should be aware of, especially turbocharged ones.
1) Octane Rating: The highest octane fuels you might see now are 91, instead of 92. This may be an issue for cars with certain performance chips, high compression ratios, and forced induction. 91 octane is, IMHO rather marginal unless this is taken into account when undertaking any program of performance enhancements.
I've posted a matrix chart on our website for blending 91 octane pump gas with 100 octane unleaded race gas. I hope this helps. Look at the URL below.
2) Elastomer Compatibility: This is largely an unknown as the long-term database is incomplete. For certain, Ethanol is well known to attack and slowly dissolve certain rubber parts used in all fuel systems. You may not get the long life expected from such items and this deserves some scrutiny. Ethanol is also an excellent solvent and scours out all dirt, rust, and contaminates in the fuel system sending them into the filter. This causes rapid filter clogging and immediate fuel filter changes are recommended along with more frequent changes than the Factory recommends. This will stop your car dead! Change that filter at least twice a year.
Last, octane boosters are not recommended except in emergencies. The additives in any effective octane booster leave a big brown mess inside your engine and they do not improve octane proportional to costs. Further, these additives WILL attack the rubber gaskets, O-rings and seals with the attendant troubles that this will create in the long term.
Lets Talk about Porsches
Instructor
Joined: Jun 2001
Posts: 185
Likes: 2
From: Tinley Park, IL
Steve,
Here in Illinois, the high octane pumps have a 93 rating and i'm sure every pump in town has the disclaimer:
"This fuel contains up to 10 (I may have also seen 15) percent ethanol."
Why a higher octane rating- lower emission requirements in IL? - around here?
IL has been blending ethanol for years and I haven't seen the filter clogging issue before. I'm no expert on fuels and I am an average wrencher at best, i'm just wondering why I haven't seen any fuel-related problems with my vehicles. My turbocharged Talon does run like crap sometimes, so maybe it's the fuel.
Thanks.
Here in Illinois, the high octane pumps have a 93 rating and i'm sure every pump in town has the disclaimer:
"This fuel contains up to 10 (I may have also seen 15) percent ethanol."
Why a higher octane rating- lower emission requirements in IL? - around here?
IL has been blending ethanol for years and I haven't seen the filter clogging issue before. I'm no expert on fuels and I am an average wrencher at best, i'm just wondering why I haven't seen any fuel-related problems with my vehicles. My turbocharged Talon does run like crap sometimes, so maybe it's the fuel.
Thanks.