Gasoline questions for @Impaaked

A recent contributor (@Impaaked) mentioned that he/she is a professional gasoline blender. Since we get many questions about gasoline on this forum, perhaps we could list some of them here and hope that @Impaaked might answer them with professional knowledge.

Some examples:

  1. How much energy loss can be attributed to the ethanol in (up to) 10% ethanol blends used in many parts of the country (as compared to pure gasoline)? Theoretically speaking, 10% ethanol should have only a few percentage points less energy than pure gasoline, yet some users swear that their vehicles get significantly worse MPG using 10% ethanol, while others say they notice no MPG loss.

  2. What is the difference between mid-tier and top-tier gasoline blends, and is it worth paying extra for the top-tier gas?

  3. Since gas is dispensed by volume, is it advantageous to buy gas when the ambient temperature is low, thus increasing the density of the liquid gas and getting more gas per unit volume?

  4. What other useful gasoline tips can you give to the average driver?

I think #3 is an old wives tale since the gas tanks are under ground at a fairly constant temperature. Once in the car though temps can expand it.

As long as we’re making work for the new guy(!) I’d like to know if the new, lower sulphur gasoline is fully backwards-compatible with the injectors on my 1994 F150, or would he recommend tossing in a top oil or similar lube?

Personally, I’m wondering if we’ll hear much from the new guy

Not pessimistic, just wondering

I’m looking forward to reading what he has to say

Ethanol has only 70% of the energy content of gasoline. Therefore with 10% ethanol you should get about 97% of the mileage of regular gasoline theoretically. And E10 should have to be at least 3% less expensive than normal gasoline.

Top Tier gasoline costs no more than non-Top Tier gasoline where I live.


Think he might be confusing the Top Tier rated gas products like at Kwik Trip with regular, mid-“grade”, or high test premium at the pumps. Only some brands have achieved the top tier requirements and don’t cost any more than at other stations.

The cheapest gas in my neighborhood ($3.04) is offered by a “Top Tier” marketer. The next cheapest, Costco, also top tier…

(Lakewood, Colorado)

@Docnick, yes, we’ve done that calculation here before, yet some drivers still insist that their vehicles get much lower mpg on 10% ethanol.

One could argue that flame-front propogation is slower with EtOH, and would therefore burn less efficiently in a engine not designed around it, and not running any timing advance. I don’t know if it’s true or not, but I’m willing to consider the possibility.

I think it varies greatly by car. My 92 mopar minivan got terrible mileage on 10% ethanol, My 2002 got about 2mpg less and my 2012 Camry doesn’t vary/

On my 89 Mustang GT when they started this 10% ethanol game I could feel the difference in throttle response using E-10. I did notice my fuel mileage drop a bit. Now that Florida has over rode this mandate I have been using 89 octane ethanol free. A lot of stations now have this 100% gasoline and have noticed a more smoother throttle response and my GT runs so much smoother…My car was never designed to run on that 10% junk and no damage done as far as I can tell…

Using this 10% on my weed eaters and lawn equipment resulted in carburators that were damaged by the ethanol. I lost 2 weed eater 2 cycle engines in 3 years. It eats the rubber hoses and seals and one weed eater it actually destroyed the inlet fuel line inside ( got hard as a rock and cracked ) and clogged up the carb.

On my lawn tractor, when shut off would dump and entire tank of gas through the exhaust over a period of 2 weeks…due to damage with the seals causing fuel to drip through the needle and seat… I had to put a fuel shut off valve on the gas tank until I could get the rebuild kit.

I now run pure gas in everything for the past year or so and no more problems…I have to pay 30- 40 cents more a gallon but well worth it. The GT can get away with 87 octane and adding just 2 points of octane should not hurt anything…

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.

Excellent, thanks for your wisdom. :wink:

that was a great discourse that seemed very uncontaminated, even though you are close to Alberta tar sands.

keep up the great info. I for one appreciate the straight info. gene

that was great, but I was under the impression that Venezuela did not produce light sweet crude…


Venzuela produces a variety of crude.

The real sticky stuff was mixed with water to make an emulsion for burning in power plants. Florida Light & power used it for years. It was called the “fuel from hell” because it contained all sorts of contaminants.

The stuff from Lake Maracaibo is relatively light and has been flowing for a very long time. Inland there is heavier oil as well as very sticky stuff from the Orinoco belt. This requires upgrading and cleaning up to make it into a crude that can be made into motor fuel.

Most oil from Venezuela contains Vanadium.

thanks, I had heard that much of the crude from there had to be refined at gulf coast refineries because they were the only place that could handle their heavy oil. or the only place within a reasonable distance anyway. I was not aware they had many types of oil

Interesting read and the only things I will add is that I’ve never actually run across any “bad gas”.
Any contaminated gasoline was due to outside factors and had nothing to do with the refining process.

Back in the old days a few of the younger guys whom I knew used to go out into the oil field at night and pirate drip gas from the wells. This stuff was essentially swill and often caused an engine to smoke and knock like crazy.
Refined gas was 30 cents a gallon so why get gouged at the pump… :slight_smile: