Do different Gas Brands burn more efficiently? Higher MPG's?
 

I've noticed some people here and on other forums say that they have had a 10%+ improvement by buying gas at a different retailer. Will (for example) gas from Shell get me higher mpg's when compared to Costco gas? I would think it doesn't but people seem to stand rather firm on the idea. Thoughts? Data? Thanks.
- Aaron

i've found a 10% mpg difference due to the presence or lack of ethyl alkyhol (e.g. E10), since alkyhol has less energy content than pure gasoline. Check out pure-gas.org to find alky-free stations and make your own test. Gasoline is for driving, alkuhol is fer drinkin...

My experience w/ different brands of gas.
 

Yes, I have noticed up to 10% better gas from Shell. But it was only on one fill up. The improvement is not consistent. My hunch is it depends on each delivery that the station gets and that independent stations have slightly lower odds of getting the longer burning fuel. I'm not surprised that this happens considering the complexity of gasoline.

In Europe, so-called premium gas doesn't give any detectable Fuel Economy benefits.
With some of our premium diesel brands though, you can gain up to 3% better FE (error margin is 1%).
(You still lose out on price, as these premium diesels are a lot more expensive.)

That's with scientific testing - repeatedly driving the same profile on a testbank.

There are stations that sell cheapo gas, the best way here in WI to account for FE differences is tank to tank varience. After tank to tank variance you will notice if you do the alcohol percentage test that certain stations sell 87 octain fuel that is the full 10% ethanol mixed with 83 octain crap gas, other stations only have a few percent ethanol and mix with 85/86 octain fuel. You will find that there is a difference in fuel economy because the physical composition of the fuel is different, also understand vehicle tune has a lot to do with this.

A few years ago the ethanol station sold true blue E10 mixed with real 87 gas for 89 octain, my car seemed to get better FE on this than Kwiq trip crap gas 87 octain but the difference was only a few percentage points over the long run, sadly the ethanol station sold out and now also sells crap gas.

Ah well

Same here.
Premium unleaded gives a slight improvement in mileage (or kilometerage since we are metric) but the retail price means it costs about the same to travel a given distance.
This has been tested repeatedly by motoring organisations , consumer mags and current affair TV shows.

Diesel is a different ball game on this side of the equator since politics and taxation play as much a part as the actual consumption does.

Peter.

I took the liberty of starting a poll on this:http://ecomodder.com/forum/showthrea...nce-23553.html

Thanks for the responses thus far! I was also thinking of including a Poll but then I thought that MPG's aren't an opinion, they are verifiable through data. It would be great if someone were willing to do a few runs on different tanks of gas from different stations and get a true test out of this with real numbers!

Sure. I was just curious what the perception of people around here was. Doing real world testing of this is tricky because so much else changes between tanks other than just the fuel (weather, traffic, etc.). Also, there may be batch-to-batch variations at all the different stations.

The batch to batch variation would probably be the most difficult to control. I still want to see someone attempt this!

I started testing a mix of 87 e10 e85 and 91 ethanol free

Thus far my lie o-meter reads 60mpg on flat ground when before it topped at about 53mpg on the same stretch but only if my motor is warm, my startup/warmup FE is MUCH lower.

Very odd effect.

My test mix is
50% e10
30% e85
20% 91 e0

The car hops less accelerating during warmup.

Well Lie-O-Meter is behaving the same average per it is 47.8mpg ave on this mix and I am in my in town cold weather mode so I expect it to drop further, trouble is my father also drove the car (-3mpg on a 150 mile tank) and its getting cold which takes off 5 to 10mpg on this car easily.

This is actually doing "well" considering the amount of higher speed driving and town driving was done in colder weather. I will know when I eventually fill up if this mix paid off, was a wash (I lean to that choice) or cost more $$$

I chose the mix based on the fact that it cost the same price as plain e10 but had much higher octane, it appears the octane on a 2.2ltr 10.5:1 compression ratio car wins out over the additional ethanol in the tank.

The ethanol MASSIVELY affects my acceleration FE during warmup, bleh 9mpg instead of 18mpg sucks.

Ah well

That's a lot of E85! Just for kicks I decided to add 1.3 gallons of E85 to the 9.2 gallons of 87 (we only have E10 in California) and maybe 1 gallon left in the tank, for a 20% ethanol blend. The E85 was rather expensive at 3.89/gallon, but this was just to see what would happen. I had a tiny bit of knocking at low speed even after "steam cleaning" my engine, so I was thinking maybe running some more alcohol would help wash it out a bit more. I figured just 1 tank of E20 can't be any worse than pouring some fuel injector cleaner stuff in, and though I lost about 1 dollar because of the E85's price, my octane rating is probably bumped up a little so it's just like buying 89 instead of 87 or something I figure.

Observations so far: engine seems a little smoother, but I did switch from Chevron to NTG so maybe there is a gas blend difference. Cold idle seems to be a little rougher, but not sure. MPGs don't appear to be affected, but it's obviously going to be hard to tell. Engine doesn't idle consistently and seems to have slightly out of calibration O2 sensors as the exhaust always smells a little like unburned HC, so that's another unknown. I should log the timing sometime, I think it was a little lower than normal last time, hopefully the ethanol is allowing full advance.

Not really, I have run up to 60% e85 in the past and that was on a 98 buick. The cobalt seems to have no issue with any ethanol blend but it does kick the MPGs down a lot if I am more than 30% ish.

Normally I don't mess with E85 anyway because its not $0.99 a gallon anymore like it was 7 years ago. Thus not worthwhile but with gas prices higher than normal I thought about testing the $3.499 e85 with non-e10 87 octane gas (most of the stations aren't selling it again, blast!)

Anyway this was mainly to test the fuel economy and performance aspects, I don't get the hop I normally get during cold starts but other than that performance seems similar (to the butt o meter) and FE per the lie o meter is within the margin of error but I definitely notice poor fuel economy during start up and better than expected once warm. So for cold weather in town = bad, highway = good

I see. Yea at 3.89 a gallon I knew I was getting ripped off, but I am treating it as a cut price octane boost of sorts, and hoping that it will have some cleaning effect.

At 20% ethanol I didn't notice any different behavior other than an idle that dipped lower than usual for a few seconds making some unhealthy noises, and a more inconsistent idle while driving as the engine was adjusting the fuel trims or something. Engine was warmed up though, and no fuel economy loss apparent. This morning I started it at ambient (18C I think?) temperature and drove, felt exactly like using normal gas according to the butt-o-meter. Did not use the mpg gauge though, since I didn't feel like pulling out my phone. Supposedly 20-30% ethanol is the best for thermodynamic efficiency in some tests, I'm guessing it's a port injected engine thing where going too high in ethanol + port injection doesn't cool the charge enough to offset the unvaporized ethanol wasting some of the heat of combustion, whereas a direct injected engine makes better use of the cooling effect of ethanol and will see greater improvement from running a higher amount of ethanol.

I can't believe you guys are running anything higher than E-10 in your vehicles that are not equipped to handle such high levels of Ethanol. Are you not worried about wearing out seals and what not? EPA just mandated that all cars must fill with at least 4 gallons of gas if the station has E-15 or higher on the same pump. Be careful!

A lot of people in the E85 community say there's no problem with the fuel system, that they've been running E85 with only upgraded fuel pumps and injectors for years without issue. The EPA seems to think that E15 is safe though car manufacturers don't.

The fact that the car manufacturers think it's bad makes me too afraid to run it all the time, besides the price isn't very good out here in California, but putting ethanol into this tank is more because I want to clean my engine and supposedly ethanol is good for that. I also want to see if boosted octane rating makes it smoother at all. I figure it can't be any worse than dumping a bottle of some unproven snake oil that goes for 10 dollars into the tank.

The reason e15 could be bad is some engines use exhaust valves that can't handle the heat. If you want to know you'd have to figure out what type exhaust valves you have.

I say MYTH ??? That only happens if your car runs lean during WOT, any modern car with an O2 sensor can handle E15 (or e30 for that matter) Just don't press the gas pedal to the floor, closed loop only please.

AKA running at stoich ethanol burns MUCH cooler than gas so no burnt valves.

Filled up the Impala with 3.02 E85 over the weekend, 1/6 less is what it takes to be worthwile for it, 3.65 v 3.02 was close enough. Driving it 9 miles home after filling factory gauge displayed 32 mpg (50 mph). I'm sure my wife will pull that down.

Haven't blended any yet in the Cobalt but last 3 tank comparision E0 to E10 was only 1.6% loss of mpg and about 2.8% cheaper. (44.4 vs 43.66mpg) probably not a statistical difference.

Heats of combustion (kJ/kg) of different fuels:

Methanol (CH3OH).....20,000
Ethanol (C2H5OH).....26,800
Gasoline.............43,700
Diesel...............44,400

source: http://www.nrc.gov/reading-rm/doc-co...1805/ch3-6.pdf

That's not per equivalence oxygen though. Per equivalence oxygen I think the alcohol fuels have about the same heat of combustion, maybe ever slightly more, maybe slightly less I can't remember. I am pretty sure the usual quoted heats of combustion are going from liquid state fuel, so they include latent heat of vaporization. I believe gaseous ethanol combusting produces about the same amount of heat.

With insufficient timing the slower burn of ethanol could possibly give rise to higher exhaust temperatures, but I imagine this would be very hard to actually accomplish. Moreover, the most heat sensitive thing in the exhaust stream is not the valves but rather the catalyst, and manufacturers tune their engines to protect the cats.

The thing with ethanol is that because its latent heat of vaporization is significant, even compared to its heat of combustion, it's very sensitive to how the fuel is delivered and vaporized. Ideally for efficiency you'd want all the fuel to vaporize in the chamber after the intake valve seals, to reduce the work on the compression stroke. Direct injection systems inject on the intake stroke and maybe a second time on compression because they need time for the mixture to form, so no engines actually take full advantage of the cooling effect for efficiency. What you can do is cool down the surfaces in the engine a bit to quench potential hot spots that could cause knock, and cooling the intake charge a little helps too.

However some engines end up with unvaporized ethanol at the end of the compression stroke, and these will see near the full 34% loss of "fuel economy". I think this happens to some extent on a lot of current crop flex fuel engines because they're not doing so well in fuel efficiency. In this case, the exhaust temperature is definitely going to be lower.

While I like the conversation about the Ethanol fuels, I would like if someone would focus a little more on the brand to brand comparison if possible! I would do this but I fill up once every month or two so...

The reason you are getting talk of ethanol fuels (which almost every fuel on the market is) is because that is the main factor of variation between one gas station and another.

You will find certain stations have different additives and different ethanol blends, some include more napathylene others don't have a winter blend of gas on certain grades.

The thing is (in my experience) is that from one week to another the same gas stations can have a swing in ethanol content (spot price varies), unless they GUARANTEE ethanol free but then those that have ethanol free may add MTBE or whatever that crap is called, which on my car kills FE more than ethanol.

So what I am saying is that this is sort of a unicorn, there are ethanol test kits on the market that aren't real bad $$, there are also a few sites that exposes who uses MTBE but beyond this, empiracle don't mean squat.

To make this thread into a non-unicorn we would need some sort of chemist kit and someone willing to do analysis, trouble is in my area there is a MONOPOLY in that ALL FUEL COMES FROM ONE SUPPLIER with only 2 exceptions in the whole area where I live. Does not matter what brand they slap on, comes out of the same tank.

This means the only differences between stations are the additive package and possibly ethanol content (to a point)

AKA the same tank fills BP & SHELL, they just blend in some additives from the as-is gas from the supplier.

Cheers
Ryan

Shell vs. Unocal 76
 

I have a very routine, lengthy commute m-f with 60 miles of straight highway driving each way. I drive a 2014 Ford Focus SE Hatch. I've always used shell 87 in this car and was steadily getting 38 MPG per tank. I decided to try Unocal 76 87 octane since I used them years ago. I started getting 42 mpg per tank. I continued to use Unocal 76 for a long while and continuosly got over 40 mpg per tank. I recently switched back to Shell 87 Octane just out of curiosity. Sure enough mpg dropped down to 37mpg?! There is clearly a difference between Shell 87 octane and Unocal 76 87 octane. I drive the same route everyday, at the same times, with cruise control set at 70, and used each brand of gas consistently for weeks at a time for comparison. I'm confident the differences are due to the fuel.

Time of year (summer-blend vs. winter-blend) could cause similar results.

Good point. I did think about the summer/winter blend. I didn't consider it much since I used both during the Spring and weather here in Cali is consistently mild this time of year. I switched back to Shell in the past month (beginning of April). Since I commute a lot, I get gas rather frequently. The change in mpg was noticeable on the first tank after switching, which I thought was just my imagination, but it has been consistently 36-38 mpg since I switched back to Shell in April. Prior to April, 40+ mpg consistently using 76. Not a big deal I guess, just found it interesting enough to google the topic and find this thread lol :) Shell offers much better reward incentives (discounts, etc) than 76 does, which is why I gave them another shot to reduce fuel costs. But over time it probably balances out the same.

...only your gas bills will know/prove which is right (ha,ha).

Wish some scientist could come on here, grab fuel from a few popular stations, and test them all to discover what could be triggering the differences!

Don't need to be a scientist.

Get an ethanol test kit.

Locally fuel marked may contain up to 10% ethanol many times doesn't.

Smaller stations sometimes have more heavy ends, a few states allow non oxygenated fuel (as I discovered out west)

I always get gas for Ron Burgundy at the same Circle K, at the same pump, at the same time in the morning, to the second click of the pump.

I don't know about different gas at different places affecting mpg, but I do try to make sure my tank-to-tank numbers are as legit as possible and reduce the variables as much as possible.

Now in my wife's 2014 Explorer, I'll get gas wherever it's convenient.

Shell Gas
 

I was a delivery driver for an auto dealership in SoCal for about half a year. I drove the truck and saw it as a perfect chance to test out different gas stations.

I would always do the same sort of routes throughout the week and my tank would last about 3 days. So i kept track of the gas and these are the main points i found:

Every single tank I had that was Chevron or Texaco was the WORST. I can't overstate this enough. every. single. tank. from chevron or texaco. was the worst.

Shell was always the best. every single time. not by a lot, but it was on average 1.5-2mpg better than chevron/texaco.

Really dinky gas stations with no brand name were completely unpredictable. one particular station was almost as bad as chevron/texaco, consistently. Others were right in the middle. but they usually were not up to par with shell.

I couldn't test ARCO or Valero, those ones are supposedly the crappiest, but I can't confirm it or deny it.

This was in a 5.3 Chevy V8 1500 Truck with 88k miles and the AC on full blast at every second of it's life. Averaged between 16.3-18.8mpg in mixed driving.

I saved my MPG sheet somewhere but I can't find it for the life of me.