TheWizard Posted April 12, 2013 Report Share Posted April 12, 2013 (edited) Higher octane is more resistant to pre-ignition and detonation (knock) allowing more ignition timing advance which in turn creates more power. Recent Ford engines - in particular the EcoBoost series and the 5.0 Coyote - have a new power control module (PCM) that incorporates "adaptive timing". The new PCM works in conjunction with the knock sensors to advance the timing as far as practical for the octane of fuel in use so there is more timing advance (hence more power) with higher octane than with regular 87 octane. Older engines (in particular, the non-EcoBoost 3.5L V6) also have knock sensors but they are programmed to work in the opposite direction. The PCM has a preset amount of ignition timing advance programmed that it will reduce if the knock sensors detect a problem from lower octane or bad fuel. Since the PCM is programmed with its maximum timing advance based on regular 87 octane fuel, using higher octane provides no benefit. My old LS1 Trans Am was also programmed that way but based on 91 octane "premium" fuel. It would run on 87 octane without damage but the performance and mileage suffered significantly due to the timing being retarded by the PCM to avoid engine knock. On the other hand, it gained nothing by running on 93 octane because it wasn't programmed to advance the timing beyond the 91 octane starting point. The point is that higher octane fuel by itself will not increase either performance or mileage - additional tuning in the form of ignition timing advance is required to take advantage of the increased octane. EDIT: I should mention that in some areas of the country, premium fuel is not just higher octane but also ethanol free. That would make a significant difference in both mileage and performance because gas has 35% more energy than ethanol. But I don't think that would apply to you because I don't think there's anywhere in Florida that does that. Edited April 12, 2013 by TheWizard 3 Quote Link to comment Share on other sites More sharing options...
Eatinitup Posted April 12, 2013 Report Share Posted April 12, 2013 Higher octane is more resistant to pre-ignition and detonation (knock) allowing more ignition timing advance which in turn creates more power. Recent Ford engines - in particular the EcoBoost series and the 5.0 Coyote - have a new power control module (PCM) that incorporates "adaptive timing". The new PCM works in conjunction with the knock sensors to advance the timing as far as practical for the octane of fuel in use so there is more timing advance (hence more power) with higher octane than with regular 87 octane. Older engines (in particular, the non-EcoBoost 3.5L V6) also have knock sensors but they are programmed to work in the opposite direction. The PCM has a preset amount of ignition timing advance programmed that it will reduce if the knock sensors detect a problem from lower octane or bad fuel. Since the PCM is programmed with its maximum timing advance based on regular 87 octane fuel, using higher octane provides no benefit. My old LS1 Trans Am was also programmed that way but based on 91 octane "premium" fuel. It would run on 87 octane without damage but the performance and mileage suffered significantly due to the timing being retarded by the PCM to avoid engine knock. On the other hand, it gained nothing by running on 93 octane because it wasn't programmed to advance the timing beyond the 91 octane starting point. The point is that higher octane fuel by itself will not increase either performance or mileage - additional tuning in the form of ignition timing advance is required to take advantage of the increased octane. EDIT: I should mention that in some areas of the country, premium fuel is not just higher octane but also ethanol free. That would make a significant difference in both mileage and performance because gas has 35% more energy than ethanol. But I don't think that would apply to you because I don't think there's anywhere in Florida that does that. Very good info.. Thank you for outlining that. I didn't want to seem like a pest, I just love to learn new things! Quote Link to comment Share on other sites More sharing options...
TheWizard Posted April 12, 2013 Report Share Posted April 12, 2013 No problem at all... I never mind explaining one of the (few) things I know the most about if it can be helpful to someone. Quote Link to comment Share on other sites More sharing options...
Tarek Jajeh Posted April 21, 2013 Report Share Posted April 21, 2013 (edited) Higher octane is more resistant to pre-ignition and detonation (knock) allowing more ignition timing advance which in turn creates more power. Recent Ford engines - in particular the EcoBoost series and the 5.0 Coyote - have a new power control module (PCM) that incorporates "adaptive timing". The new PCM works in conjunction with the knock sensors to advance the timing as far as practical for the octane of fuel in use so there is more timing advance (hence more power) with higher octane than with regular 87 octane. Older engines (in particular, the non-EcoBoost 3.5L V6) also have knock sensors but they are programmed to work in the opposite direction. The PCM has a preset amount of ignition timing advance programmed that it will reduce if the knock sensors detect a problem from lower octane or bad fuel. Since the PCM is programmed with its maximum timing advance based on regular 87 octane fuel, using higher octane provides no benefit. My old LS1 Trans Am was also programmed that way but based on 91 octane "premium" fuel. It would run on 87 octane without damage but the performance and mileage suffered significantly due to the timing being retarded by the PCM to avoid engine knock. On the other hand, it gained nothing by running on 93 octane because it wasn't programmed to advance the timing beyond the 91 octane starting point. The point is that higher octane fuel by itself will not increase either performance or mileage - additional tuning in the form of ignition timing advance is required to take advantage of the increased octane. EDIT: I should mention that in some areas of the country, premium fuel is not just higher octane but also ethanol free. That would make a significant difference in both mileage and performance because gas has 35% more energy than ethanol. But I don't think that would apply to you because I don't think there's anywhere in Florida that does that. i just got ford explorer 2013 xlt (3.5L v6) non Eco-Boost in the owner's manual they are saying: " 3.5L V6 engine: Regular unleaded gasoline with a pump (R+M)/2 octane rating of 87 is recommended. Fuels with octane levels below 87 are not recommended. Premium fuel will provide improved performance and is recommended for severe duty usage such as trailer tow. " does this mean if I use fuel with octane 93 (or higher) will be better ? or at least it will not damage my car ?? Edited April 21, 2013 by Tarek Jajeh Quote Link to comment Share on other sites More sharing options...
WWWPerfA_ZN0W Posted April 21, 2013 Report Share Posted April 21, 2013 Tarek, any gasoline 87-93 octane should be fine for your Explorer. Performance should be improved with 93 octane, though can't speak for how your MPGs are affected. Quote Link to comment Share on other sites More sharing options...
Tarek Jajeh Posted April 21, 2013 Report Share Posted April 21, 2013 Tarek, any gasoline 87-93 octane should be fine for your Explorer. Performance should be improved with 93 octane, though can't speak for how your MPGs are affected. Thanx for the info actually all i wanted to know does higher octane damage engine or not . one more thing, by going to owner's manual again found that the note of Premium fuel that was for the Eco-Boost engines, but the engine i have is non Eco-Boost engine. so i think it is clear now. :D Quote Link to comment Share on other sites More sharing options...
akirby Posted April 21, 2013 Report Share Posted April 21, 2013 Higher octane won't damage any engine but it also won't help most engines and is a waste of money. Some engines, like yours, will benefit from advanced timing when using premium yielding more power and better mpg. But it's probably not enough mpg improvement to make up for the higher cost of premium which is why Ford only recommends it for better performance when towing, etc. Quote Link to comment Share on other sites More sharing options...
arabski Posted May 29, 2014 Report Share Posted May 29, 2014 ...after reading here I started using 91 on my 2013 sport (most of the Middle Eastearn countries offer either 91 or 95) and the only negative side is that it smells really bad on cold start when you pass by the rear of the car... it didnt notice the smell when on 95... 1 Quote Link to comment Share on other sites More sharing options...
rossid Posted May 30, 2014 Report Share Posted May 30, 2014 87 seems to work just fine on the 2008. Speaking after just two weeks of ownership. Quote Link to comment Share on other sites More sharing options...
WWWPerfA_ZN0W Posted April 18, 2015 Report Share Posted April 18, 2015 A handy reference to modern gasoline formulations: http://www.ethanolrfa.org/page/-/rfa-association-site/ChangesinGasolineManualIV-UpdatedLogo.pdf?nocdn=1 ChangesinGasolineManualIV-UpdatedLogo.pdf Quote Link to comment Share on other sites More sharing options...
PrinzII Posted April 28, 2015 Report Share Posted April 28, 2015 From my experience on the highway, there seems to be a difference between NM, TX, OK, and MO gas versus that of AZ. I got the best mileage out of NM gas and the worst out of MO and even IL. Quote Link to comment Share on other sites More sharing options...
rwf78155 Posted April 28, 2015 Report Share Posted April 28, 2015 Dont fool yourself with brands of gasoline My dad used to be a regional distributor for Gulf and when Gulf ran low he would get gasoline from Exxon or Texaco Quote Link to comment Share on other sites More sharing options...
pjazz Posted April 30, 2015 Report Share Posted April 30, 2015 I use what the manufacturer recommends. My last 3 three cars corvette which i still have, Cadillac STS and BMW recommended Premium. I read the same long thread on other forums but it was the other way around that you didn't have to use premium because the car is calibrated to adjust timing, I just use whats recommended because manufacturers did the testing for me and I don't have to guess whats better.. Quote Link to comment Share on other sites More sharing options...
PrinzII Posted November 30, 2015 Report Share Posted November 30, 2015 Lately, it's been Arco and QuikTrip that's been pretty decent for me. Mobil and CircleK are second. Shell is third. Chevron is still the worst. Quote Link to comment Share on other sites More sharing options...
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