Hi folks. New guy here. Sorry to not respond but working late nights to engineer new controls for a local college campus, so I have limited time (as I’m sure we all have). So db4690 is right, new guy may not spend a lot of time here, but here’s another long discourse…
jesmed1, I’ll answer each question in turn to the best of my limited knowledge.
Q1: I believe the response on ethanol below by Docnick is correct. It has a lower energy density (but higher Octane number) than that of typical straight-run gasoline blends. Ethanol is an important component in Oxygenated blends that reduce CO and unburned gases. We used to use amazing stuff like MTBE, but it contaminates groundwater and is less often used, eventually to be phased out. Bear in mind that to truly dial in your mpg, you should do the calculation over 4 or 5 tanks. This is to average out all the other external inputs that affect your mpg (more hills on this drive, more stoplights, etc.). I’ve done this and it dials it in better. Thru this I found that my Honda Fit takes about a 4 mpg hit with the 2 bike and 2 kayak racks on top.
Q2: As for on mid/top tier blends, you get a higher Road Octane Number, what we see on the pumps as “Octane”. It also has detergents, stabilizers like corrosion inhibitors and antioxidants, dye (sometimes), and anti-knock compounds. My engines doesn’t need the higher octane, so I only fill the tank with top tier a couple times per year, mostly for the detergents.
Anti-knock compounds boost octane to avoid pre-detonation. Lead (TEL) is no longer used, and we still use MMT here in Canada, but it’s restricted in the US. Ethanol is considered an anti-knock compound.
Recall that the Octane number at the pumps is the average of Research Octane (RON) and the Motor Octane (MON). Don’t believe that every gas is identical for a particular refinery. For example, we would blend a 50,000 barrel tank to 87 Octane. One blend may have really high RON, balanced out with really low MON, providing 87 Octane. The next day, it may be lower RON but higher MON, again providing 87 Octane. However, you’re engine is a complex machine and may respond slightly better with one blend than the other. Blending is based on the quantity of the feedstocks available to blend, which can vary daily within each refinery.
Q3: Bing is correct, most gas station tanks are underground and hence usually at a stable cool temperature, hence there’s negligible temperature expansion. I guess if the tanks are located far away, there would be some temperature rise before it gets metered at the pump, but again, likely negligible. Once the gas is in your vehicle, all bets are off.
Q4: Gas tips for the average driver? Burn calories, not gasoline! Greenhouse Gases are a real concern and everyone needs to act, now! Yes, I’m a hypocrite with my wife’s Honda Fit, our F250 w/camper and my Suzuki Supermoto bike. That being said, they usually sit in the driveway since she usually cycles to work. We cycle and walk as much as possible. It helps that we live in a small city of 50,000 in the mountains in the interior of British Columbia.
meanjoe75fan: Not sure on the low sulphur gases. I’ll defer that to someone who knows. I do know that the sour crude (high sulphur) we extract from the incredibly dirty Alberta tar sands kills our fuel pumps, fast. It’s quite the phenomena. Refineries do have desulphurization units, but gas blends still contain higher sulphur contaminant levels than the sweet crudes from the Middle East and Venezuela that typically feed the eastern refineries.
Howie32703: Your experience with ethanol blends is interesting. Something I’ll look for, however my vehicles aren’t near the performance machine you have. Perhaps it’s more important to get a blend that works for you.
Lastly, one thing that always gets me is when people say “X brand of gas sucks”. If one knows the truth, not only do small independent gas stations get their fuel from different refineries, sometimes the big boys do too. I remember seeing a Chevron tanker filling a Shell station back in Ontario. It happens a lot, usually with independent 3rd party tankers so the logo isn’t evident. To single out a particular brand is also nonsense (exception below), since each and every blend is different. That being said, when it comes to top tier gas, one refiner may use different additives that you like more than another, hence there can be differences between brands.