Best treatise I've seen on the subject. Factual and unopinionated discourse:
Thank you to my friend for posting elsewhere
Post by Pterodactyl Ľ Wed Jan 23, 2019 5:41 pm
Ethanol Info from an Expert
On another forum a lad posted a response he got to some questions he asked a SUNOCO technical guy. I thought them interesting:
Yes, all Sunoco pump fuels (87-93AKI) are Top Tier and have the same level of ultratech detergent. Sunoco Race Fuels that are unleaded (95-104AKI) also contain a high level of UltraTech detergent but are not officially Top Tier. Our Race fuels have always exceeded performance requirements of Top Tier but we have not submitted them for certification because Top Tier is directed at pump fuel issues. Sunoco Race Fuels have been tested to be about 10 times cleaner than pump fuels.
Octane is a measurement of resistance to pre-ignition, detonation or spontaneous combustion. There are many factors that influence the octane rating required for each engine. Some of those factors are compression ratio, engine operating temperature, Air/Fuel ratio and bore size. Following the manufactures octane recommendation will ensure that the engine isnít damaged from octane related problems. Using a higher octane fuel wonít hurt performance and is like having more insurance than you need. Octane is only one of many important factors that control how a fuel performs in an engine. Since octane rating is how we choose different grades at the pump many people latch on to that being the only difference between the fuels.
Ethanol in fuels is an endless topicÖ Ethanol can be spun in many ways so I will try to only provide facts and not opinions.
Ethanol has a lower energy density(Btu/Pound) than gasoline (11,500 vs 18,600).
Ethanol has a higher liquid density(lbs/gallon) than gasoline (6.60 vs 6.08).
The above numbers can be rearranged to show energy density as Btu/gallon. Ethanol is lower than gasoline (75,900 vs 113,100) a 10% ethanol blend will have about 4% less energy per gallon and this can be seen in real life as fewer mpg.
Ethanol is about 35% oxygen by weight. Fuels with oxygen in them will increase efficiency of the engine and allow for overall better performance. A 10% ethanol blend will have better performance than a pure gasoline fuel. The difference in performance is about 1% for this case. 100 HP on gasoline would be 101 HP on an E10 blend.
Ethanol will readily absorb water from humid air and draw moisture into a fuel system. This is the reason lawnmowers and other small equipment will get water in the fuel. Modern cars have sealed fuel systems and donít see this issue as much. Small equipment fuel systems will typically have a vent to atmosphere which allows water to find its way in.
Pure ethanol has an excellent storage life like many other pure chemicals when stored in a sealed container. Sunoco 260 GT is 100 octane, 10% ethanol fuel. We have tested this fuel stored in drums for over 2 years and the fuel still meets all our manufacturing specs. Ethanol doesnít decrease the storage life but it can compromise fuel by bringing in water.
Pump gasoline components are not as stable as pure chemicals and stability tends to decrease with octane because lower octane fuels contain more low quality hydrocarbons. 87 octane, 10% ethanol fuel is 83 octane gasoline mixed with ethanol. The ethanol bumps the octane up to 87. Using regular grade 87 octane fuel in small equipment causes many of the issues blamed on ethanol. Small equipment is stored for months or seasons with low grade gasoline that is only designed for a storage life of a few months. This is what shows up as varnish and brown gunk in small equipment. Mix than with ethanol bringing in water and you have a situation that leads to corrosion and costly repairs.
Premium(91 or 93AKI) will have a better storage life than regular (87) and 89 is a mix of the 2 grades. Using a premium fuel will help keep the fuel system clean and reduce chances of fuel related issues. If the bike will be stored for long times like winter it would be a good idea to fill up with non-ethanol fuel with the highest octane you can find.
I hope this helps,
SUNOCO RACE FUELS