Gasoline and Driving performance

[widman]

This answers a lot about the octanes performance opinions... including the statement: "Using gasoline with an antiknock rating higher than that required to prevent knock or to prevent spark retardation by the knock sensor will not improve a vehicle's performance."
I think it is an interesting statement by someone who sells gasoline.

http://www.chevron.com/prodserv/fuels/bulletin/motorgas/ch1a.shtml

 

[userfriendly]

Widman;
Thanks a lot for posting that link. You just added two hours of reading to my day.

The comment about various fuels having up to an 8% difference in heating value caught my attention.
Does that mean some gasolines have more energy content or thermal energy (BTUs)than the next and are therefore a better fuel for the price as they will achieve more work per litre?
I noticed in testing two Honda CR125s that by switching from one brand of 94 octane (M+R/2)to another brand of 91 octane, I was able to reduce the main jet from 300 to 290, or to about 97% of the base-line jetting.
Other crew mechanics with the same year and make of motorcycle were jetting up to 310 and sometimes 320 on cooler days (depending on elevation all else being equal) in the event they were using a very high octane (and expensive) race gasoline.

I like to listen to engines. If they sound too pitchy, something is wrong with the tune-up. That applies to four stroke engines as well where header pipe length RPM , cam profile, and even exhaust valve lash are tied together.
You want to hear: BWAAAAAAAAAAAA, not WHAAAAAAAAAAAAA.

 

[MNgopher]

The answer to your question is yes!

Problem from there is determining if fuels sold under different brands are actually different or if they all came from the same terminal with different additives.

With my fuel records, I can show that I get 1.5-2% better fuel mileage on Amoco/BP/Tesoro gasoline in this market. They are the only ones who maintain a separate distribution system (ie: refinery/pipeline/terminal/truck transport) here. Everything else (except Holiday Blue Planet) comes through a shared pipeline network, so who knows which refinery it came from.

Good luck figurng out where all the fuel in your market comes from!

 

[userfriendly]

Minnesota Gopher;
It looks like your 2% fuel savings and my 3% jetting change constitutes a trend.

Is the additional 3% jetting over the base-line figure typical of race gasolines?
Where do avaition fuels fit into the puzzle?
They (av fuels) sure make jetting difficult in performance automotive engines if using spark plug colour to guage changes.

 

[Jimbo]

Avgas should have a higher heat content per gallon because it does not contain any oxygenate. It is a blend of Napthas and Toluene, with Tetaethyl lead, of course. Notice how "sweet" it smells compared to auto gas and if you spill any on your hands, it evaporates without leaving any residue behind.

Aircraft do not use fixed-jet carburators. Even the fuel injection systems have a manual mixture control knob.