Fuel information
11-10-2015, 06:47 PM
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Fuel information
Just information -- not really meant for discussion. Feel free to remove thread if not useful.
2016 RDX Owners Manual
Page 22:
QUESTION:
Is it possible to use unleaded gasoline with a Pump Octane Number (PON) of 87 or higher on this vehicle?
ANSWER:
Unleaded gasoline with a Pump Octane Number (PON) of 91 or higher is recommended.
Use of lower octane gasoline can cause occasional metallic knocking noise in the engine and will result in decreased engine performance.
Use of gasoline with a pump octane less than 87 can lead to engine damage.
Page: 17:
Fuel recommendation:
Unleaded premium gasoline with a pump octane number 91 or higher recommended.
2016 RDX Owners Manual
Page 22:
QUESTION:
Is it possible to use unleaded gasoline with a Pump Octane Number (PON) of 87 or higher on this vehicle?
ANSWER:
Unleaded gasoline with a Pump Octane Number (PON) of 91 or higher is recommended.
Use of lower octane gasoline can cause occasional metallic knocking noise in the engine and will result in decreased engine performance.
Use of gasoline with a pump octane less than 87 can lead to engine damage.
Page: 17:
Fuel recommendation:
Unleaded premium gasoline with a pump octane number 91 or higher recommended.
11-10-2015, 08:16 PM
#2
I happen to to know a thing or two about tuning engines. 
If one of you ever find yourself in a situation where you need to run 87 do the following and you'll be fine.
1. Don't let the 87 octane get old. Try to use it up as soon as you can because with age fuel loses ability to prevent pre-ignition (octane). Fuel older than 3 months from when its additives were added should be avoided. High volume gas stations are your friend.
2. If you must run 87... keep from loading the engine more than is needed. As engine load increases the PCM ramps up timing. Greatly advanced timing combined w/high compression (like our G2 RDX has) will cause pre-ignition. The knock sensor can report this to the PCM but.... the heavier the throttle input the more timing is being commanded. With the "wrong" mix of fuel octane, engine load, and throttle input there will come a point where pre-ignition will occur. If so you'll hear a "pinging" type of sound. If you hear that... BACK OFF the gas!
3. Don't put any more low octane in than is needed. If you need 100 miles worth.. don't blindly fill it up. Put just enough in to get you to a place where you can put in high octane.
btw... some fun facts
- The higher your elevation the less of a concern this is. Over 3k feet and you'll be fine running 87 on a stock G2 RDX
- The closer to sea level you are.. the more of a concern this becomes. (DA)
- Avoid using 87 on engines w/more than 100k on them. The combustion chamber will have carbon buildup. And this will only make it more likely to "ping".
- High octane fuel and low octane fuels burn at the same speed. Octane is simply the ability to resist pre-ignition.
- At light loads the PCM is constantly maxing out timing to the point where the knock sensor detects pre-ignition.
It does this to get the best possible MPG. So... it may not be noticable to the avg joe but on a small scale running high octane gives the potential for increased power. That results in less throttle.. which uses less fuel. In my work I've found the sweet spot is generally noticeable in the 45-55 mph area. (I've gone as much as 15deg timing advance in those areas and seen a solid 2mpg improvement along with crisper tip-in)
- Did you know that fresh 87 will have a higher octane than 6 month old 93?
If one of you ever find yourself in a situation where you need to run 87 do the following and you'll be fine.
1. Don't let the 87 octane get old. Try to use it up as soon as you can because with age fuel loses ability to prevent pre-ignition (octane). Fuel older than 3 months from when its additives were added should be avoided. High volume gas stations are your friend.
2. If you must run 87... keep from loading the engine more than is needed. As engine load increases the PCM ramps up timing. Greatly advanced timing combined w/high compression (like our G2 RDX has) will cause pre-ignition. The knock sensor can report this to the PCM but.... the heavier the throttle input the more timing is being commanded. With the "wrong" mix of fuel octane, engine load, and throttle input there will come a point where pre-ignition will occur. If so you'll hear a "pinging" type of sound. If you hear that... BACK OFF the gas!
3. Don't put any more low octane in than is needed. If you need 100 miles worth.. don't blindly fill it up. Put just enough in to get you to a place where you can put in high octane.
btw... some fun facts
- The higher your elevation the less of a concern this is. Over 3k feet and you'll be fine running 87 on a stock G2 RDX
- The closer to sea level you are.. the more of a concern this becomes. (DA)
- Avoid using 87 on engines w/more than 100k on them. The combustion chamber will have carbon buildup. And this will only make it more likely to "ping".
- High octane fuel and low octane fuels burn at the same speed. Octane is simply the ability to resist pre-ignition.
- At light loads the PCM is constantly maxing out timing to the point where the knock sensor detects pre-ignition.
It does this to get the best possible MPG. So... it may not be noticable to the avg joe but on a small scale running high octane gives the potential for increased power. That results in less throttle.. which uses less fuel. In my work I've found the sweet spot is generally noticeable in the 45-55 mph area. (I've gone as much as 15deg timing advance in those areas and seen a solid 2mpg improvement along with crisper tip-in)- Did you know that fresh 87 will have a higher octane than 6 month old 93?
Last edited by Mr_MDX; 11-10-2015 at 08:30 PM.
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