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Simulating the difference in gas.

3K views 36 replies 9 participants last post by  Asterisked Accolade 
#1 ·
So we've already had a thread where we talked about getting gas and sometimes the car feels less responsive, and other times the car seems to really come alive.


Now, I was thinking, if I knew what the difference was in the 'bad' gas versus the 'great' gas, I could likely simulate it with an additive. If it is just a matter of water content, you could get Sta-Bil or something of the sort. And if it is a matter of octane, you could use an octane booster to raise it a digit or two. (being sure not to go overboard with the octane booster).


So I'm curious as to your guesses about what the actual differences are in the good and bad fill ups you've had. I trust you've experienced this type of discrepancy at least once before. What are your thoughts on its basis?
 
#2 ·
I have tracked my car on 87-91 unleaded gas and from all different companies(arco, chevron, shell, mobil). Still got the same time :(. As for responsiveness, getting gas in the winter morning feels better then getting gas in summer heat ;P. The health of the motor in the long run doe, that's a debate.
 
#3 ·
I gotcha.


This last tank of gas I got feels like race gas or something-- very responsive and my engine just sounds healthier. Acceleration feels more brisk and the exhaust is extra-poppy-crackly. The tank before this one made my car feel much more docile and dull. I know I'm dealing with the ever-so-undependable butt-dyno, but I really think there is something to it. Maybe i'll run a bit of an experiment in the summer. I have RaceGas concentrate at home and I could also try something that is supposed to rid the gas of water.
 
#6 · (Edited)
It's a neat idea, though I do have a couple of naggity nags about it:

1) Additives are, at best, a bandaid for deficiencies in fuel. Even when they work perfectly, there could still be problems with uneven mixing, or side effects. (I look at such things like medications -- if it has enough active ingredient to *work*, it has enough for unwanted effects too. Otherwise, it's called a placebo. I've long since placed most automotive "additives" in that last category -- if for no other reason that these companies don't want to field damage claims from people who doubled-up their dose of $10 injector cleaner.)

2) Hate to say it, but a butt-dyno is pretty unscientific. You could compare mileage I suppose, but there are a lot of factors there too.
 
#7 ·
I find that the higher-end 'branded' fuels that tend to have more detergents in them really cause havoc with my economy. Based on a number of cars; 88 Supra, '94 LHS, '92 Grand Caravan, '05 Scion, '95 Tercel and a host of others I find Shell, Mobil, and Sunoco do the worst. Gulf does better, Irving even better and Citgo the best.
 
#8 ·
That said I do run a tank of Shell every 5-10 tankfulls because of the detergents.

I always run Premium in the Accent. It just has much better throttle response than Regular.
 
#10 ·
Tough to crack without instrumentation.

Fuel with more ethanol will have less total energy, but a higher octane rating.

Fuel with more water in it just won't work well.

There is likely something to your perceptions- use the instruments you have to glean what you can. A log of ambient temperature and tire pressure is cheap and easy, you probably already have these instruments.

Ideally you'd also tap into the car ECU and get a log of total timing advance, knock correction, intake air temp and coolant temps. Dunno if you're wired for that.
 
#11 ·
Here's something else I find interesting.


Every week I buy $12 of gas. Usually on a Friday. I have a crackly-poppy loud exhaust. So when I first buy the gas, my car 'wakes up' and my exhaust is super crackly-poppy and man my car is responsive. Then by the next week when my tank is low and I'm getting ready to fill up again, my car isn't as peppy and excited. But once I put more gas in it, it wakes right back up. I'm curious what is causing that? Does the octane deteriorate? Is there something else in the gas that deteriorates? It's just kind of weird.
 
#12 ·
If you're using corn squeezin's it's collecting water. Ethanol is like a sponge.

Gasoline does lose potency over time but not in a week.

I was thinking the other day: when I sold my '85 Corolla a few months ago, I'd be willing to bet there was still about a tablespoon of the gas that was in it when I bought it in '86. I never ran the tank fully empty, and usually filled up at the most 3/4. Usually 1/2 to 1/4 tank.
 
#13 ·
So, if water is the issue, I wonder if adding a touch of Sta-Bil would fix that; isn't that Sta-Bil's function? I'm not using anything that says Ethanol, but if I'm not mistaken, most gas has some Ethanol in it(?) Either way I'm interested in seeing if an additive like Sta-Bil would circumvent the 'potency' loss.
 
#14 ·
E10 gas will be ok in a modern car with a sealed fuel tank. If the gas absorbs so much water then the ethanol and water will drop out of suspension and nothing will help then.

I use stabil in my lawn mower gas and stored gas cans for over the winter but the car I just fill up and let sit during the snow season.
 
#20 ·
It's hard to fathom why you would be losing so much! A week should not make a difference. A couple months, maybe, but my Scion sat since December with the same gas and I can't feel a difference.

Around here the pumps say "Contains 10% ethanol" and when you do find a station that serves non-ethanol fuel it usually says "This product does not contain ethanol".

According to Ethanol-free gas stations in the U.S. and Canada the BP at

3855 Plymouth Blvdhas mo ethanol 91, and an unbranded station at Vip Auto Service
9950 County Rd 9 also has it. I'd start shopping there...;)
 
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#21 ·
Fuel stabilizers are meant for long-term protection. When you leave gasoline to sit for months, you can get some sludge at the bottom which is known as varnish, and isn't really so different from actual wood finish.

I don't know what is in gas stabilizer, but it works fine in our generators across seasons. The treated tankful doesn't burn as well, but it's a small sacrifice vs. an untreated and long abandoned tank.

I can't tell you what's going on in your tank, but here are a few things you should know:

While octane is a real substance, don't assume there is any in your gasoline. There probably is, but less than you think.

Octane rating is not the same as octane content. When gasoline are tested, a very special fuel blend with actual octane is produced for the test. It is then run through a very special stationary engine outfitted with instruments.

Then, the latest street gas formula is brought in and run through the same engine, in a series of tests. Once they have seen the engine perform with the same amount of detonation as the control formula, that fuel is then declared to match for octane rating. Mind you, it may have wildly different properties. It may produce more power or less. It can look different, smell different, be more acidic or anything really. It might have been made of rocks and leprechaun breath. Doesn't matter. As long as the test engine pings and detonates the same amount, the fuel gets the same rating.

The test is then repeated for mid-grade and premium.

Naturally, petroleum engineers are continually struggling to make more "gasoline" out of the cheapest junk they can possibly get in quantity, and this changes over time. They are also trying to satisfy lots of other requirements for engine life, emissions and power characteristics, in competition with each other.

But really the only factor it truly gets rated on is the octane equivalency.

Again, I can think of no reason why your gas feels like it's going bad in the span of a week within a sealed system. It sounds like that fuel is far more volatile than it should be.

All I can suggest is buying half as much twice as often.
 
#22 ·
As an aside, I have been getting stellar performance...when I can find non-ethanol fuel. Nearest one is 75 miles away, but I go there about once a month. Sometimes more. Sure wish I had one around the corner...:mad:
 
#23 ·
Did a 275 mile trek through Vermont today, last fillup was almost full tank of no-ethan-at-all 91 octane, with a 3 gallon 10% 93 oct top off, and mileage came out to 33.9 even flogging it through the hills. Went to the same station today, filled it from 3/4 and top off when I got home (approx 1/4 tank) revealed 39.79 MPG. I think that's the second best since I bought the car.
 
#24 · (Edited)
My fuel economy has dropped 60klm. Low heat so I odered a thermostat and rad cap because im experienced long time for coolant to get hot air in car. Ive blead air. Tested 50 50 for boiling piint ok. Will find out when I get er open I believe the thermostat is stuck open causing my engine to run off temperature thus ****** fuel economy plus the low heat is a dead give away. I check heater core already. I also pressure tested the rad with my special tools. The rad cap could be also the cause. The rubber ring looks like it pinched on the end. But because there is 0 leaks and resvoir level has no changed it might not be the cap. Cheaper to replace the cap as a precaution. Ill record this repair and dig into the hyundai tech manual and throw it up on boobtube later this month
 
#26 ·
Same 275 mile run through Vermont again today.

This time was 33.97 MPG, but I also got rid of the Winterforce "truck tires" and put on some 185/65-14s before leaving, the profile being almost 1" lower than the snows.

Refilled again with No Ethan At All.
 
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