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Weird effect from Exxon/Mobil fuels vs. Shell & others...?

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Old 10-11-2018, 12:11 AM
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Weird effect from Exxon/Mobil fuels vs. Shell & others...?

For the first ~50k miles I put on my R3, I used mostly Shell fuel, with a couple of other Top Tier Gas brands (Exxon/Mobil, Sunoco, BP) as fallbacks. With very rare exceptions, the car always fired right up, hot or cold -- even after its compression fell below Mazda’s limits.

Then, after the engine was replaced under warranty, I switched almost entirely to Exxon/Mobil fuels. No difference for the first 10k miles or so. After that, the car started taking more and more cranks to start when cold. It never got bad enough to make me worry I'd be stranded or anything; it was just noticeably slower to start than it had been. Italian tuneups seemed to help a bit, but not for long.

As an experiment, I tried switching back to my previous mix of Shell and other Top Tier brands. Over the next couple thousand miles, cold starting gradually improved. Now the car fires up exactly like it used to.

All fuels were 93 octane FWIW.

Thoughts?
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Old 10-11-2018, 05:03 AM
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Ethanol content ?
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Old 10-11-2018, 05:22 AM
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If you have a receipt you can request from the service station the fuel quality "certificate of analysis" that shows who filled the tank and what the top level tests were (EtOH content, etc.). There have been issues in the past where the local/regional blender has delivered poor quality fuel. https://chicago.cbslocal.com/2012/08...oline-from-bp/

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Old 10-11-2018, 06:20 AM
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I can say that my 04 RX-8 seems to get better mileage when using Shell gas. I used to use a local Sunoco gas station but they sold to an independent owner and the Sunoco gas station has turned into a 7/11 type of gas station. Since then I have been using Shell gas which is close to where I work and the car has jumped from 17.7 mpg to 18.8 mpg with no change in driving habits. I'm not entirely sure if its a coincidence but I have to say that I'm pleased.
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Old 10-11-2018, 07:46 AM
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After working in the petrochemical industry for the last few years, I'd be surprised if the brand has much to do with the intrinsic chemistry of the fuel.

For the most part in the US, fuels are delivered to large depots that service a wide variety of brands. Those brands then add their additive packages (mostly detergents and such), often times when they are pumped into the tanker truck for the "last mile" delivery.

The biggest impact on fuel quality is the quality of the gas station's underground tank and associated mechanicals (water control, for instance).

I'd be curious about the health of your starter and battery.
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Old 10-11-2018, 09:54 AM
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Originally Posted by Brettus View Post
Ethanol content ?
Interesting point. Not sure if Exxon/Mobil have different ethanol levels from other brands.

Would you expect something like what I described to happen with more ethanol?


Originally Posted by wannawankel View Post
If you have a receipt you can request from the service station the fuel quality "certificate of analysis" that shows who filled the tank and what the top level tests were (EtOH content, etc.). There have been issues in the past where the local/regional blender has delivered poor quality fuel. https://chicago.cbslocal.com/2012/08...oline-from-bp/
Originally Posted by NotAPreppie View Post
After working in the petrochemical industry for the last few years, I'd be surprised if the brand has much to do with the intrinsic chemistry of the fuel.

For the most part in the US, fuels are delivered to large depots that service a wide variety of brands. Those brands then add their additive packages (mostly detergents and such), often times when they are pumped into the tanker truck for the "last mile" delivery.

The biggest impact on fuel quality is the quality of the gas station's underground tank and associated mechanicals (water control, for instance).

I'd be curious about the health of your starter and battery.
To be clear, the problem I had wasn't one-off or occasional. Once it started, it stayed with me and slowly got worse over a few thousand miles. Then I changed fuels and nothing else, and the problem gradually went away and hasn't come back since.

The battery was showing signs of age, but I changed fuels and noticed the improvement well before I got my new battery. Cranking wasn't any faster after the fuel change; it just stopped taking so many cranks to start the car.
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Old 10-11-2018, 03:15 PM
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Originally Posted by IamFodi View Post
Interesting point. Not sure if Exxon/Mobil have different ethanol levels from other brands.

Would you expect something like what I described to happen with more ethanol?
r.
I know it affects starting in cold conditions if you have a high % (E85) . But I wouldn't have thought it would make a difference at low levels . Did you observe this in winter ?
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Old 10-11-2018, 03:19 PM
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Like any other car, the 8 can handle E10 stock without issues.

I personally actually notice a slight sulfur smell with Shell 91 here in Canada. Goes away with Chevron 94. Performance difference is fairly minor.

No starting difference I am aware of.
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Old 10-11-2018, 03:23 PM
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I'm running E50 at the moment and have noticed that cold startup requires more cranking time than normal . When hot it's normal ....
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Old 10-11-2018, 04:43 PM
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Originally Posted by Brettus View Post
I know it affects starting in cold conditions if you have a high % (E85) . But I wouldn't have thought it would make a difference at low levels . Did you observe this in winter ?
It might have been winter when I first noticed the problem, but either way the problem definitely persisted until the weather warmed up.
​​​​​​
Originally Posted by Brettus View Post
I'm running E50 at the moment and have noticed that cold startup requires more cranking time than normal . When hot it's normal ....
Sounds a lot like what my symptoms were.
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Old 10-11-2018, 09:26 PM
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I always heard they use different blends in the fuel for summer and winter. Some cheap crap they put in can't handle the heat or the cold or something so one part of the year you get better gas.
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Old 10-11-2018, 09:41 PM
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Originally Posted by Oats View Post
I always heard they use different blends in the fuel for summer and winter. Some cheap crap they put in can't handle the heat or the cold or something so one part of the year you get better gas.
Yep, winter gas has an additive that makes the gas vaporize more easily. It's illegal to sell that blend in summer, but I don't know how well that is enforced in the US.

That said, I would say it may just be the winter itself as well.
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Old 10-12-2018, 10:04 AM
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I've been through a few winters with this car and never had anything similar with my previous fuel mix. The rebuilt engine saw winter fuels within a month of hitting the road and had no issues then. It only happened when I had been running Exxon/Mobil fuels almost exclusively for several thousand miles, and only stopped after I switched back to mainly Shell.
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Old 10-14-2018, 12:06 AM
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Summer blends supposedly have less ethanol than winter blends. I have even heard that ethanol is eliminated during the summer. As far as Mobil Exxon and Shell, I recently heard they are the same. Several Shell stations in CO are now Mobil/Exxon. The owner claims it is the same gas ⛽. This is a recent occurrence. I haven't verified it however.
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Old 10-14-2018, 01:10 AM
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Originally Posted by Petscar View Post
Summer blends supposedly have less ethanol than winter blends. I have even heard that ethanol is eliminated during the summer. As far as Mobil Exxon and Shell, I recently heard they are the same. Several Shell stations in CO are now Mobil/Exxon. The owner claims it is the same gas ⛽. This is a recent occurrence. I haven't verified it however.
It's not the ethanol content that's higher in winter gas. It's dependent on RVP.

What is the Difference between Summer- and Winter-Blend Gasoline?

The difference between summer- and winter-blend gasoline involves the Reid Vapor Pressure (RVP) of the fuel. RVP is a measure of how easily the fuel evaporates at a given temperature. The more volatile a gasoline (higher RVP), the easier it evaporates.

Winter-blend fuel has a higher RVP because the fuel must be able to evaporate at low temperatures for the engine to operate properly, especially when the engine is cold. If the RVP is too low on a frigid day, the vehicle will be hard to start and once started, will run rough.

Summer-blend gasoline has a lower RVP to prevent excessive evaporation when outside temperatures rise. Reducing the volatility of summer gas decreases emissions that can contribute to unhealthy ozone and smog levels. A lower RVP also helps prevent drivability problems such as vapor lock on hot days, especially in older vehicles.
I hate ethanol unless we are talking about boosted cars running E85. Corn fuel isn't good for your car, hence why I use Shell 91 and Chevron 94 at where I live as these are the only E0 fuels around here. The only reason E10 is a thing is because of corn farmer lobbyism in the US(and probably Canada as well). The environmental arguments are BS as making ethanol out of corn is actually one of the most polluting ways, and transporting all that ethanol also puts out more pollution, all just so it can mess up your car... No thanks.
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Old 10-14-2018, 06:33 AM
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Originally Posted by Petscar View Post
As far as Mobil Exxon and Shell, I recently heard they are the same. Several Shell stations in CO are now Mobil/Exxon. The owner claims it is the same gas ⛽. This is a recent occurrence. I haven't verified it however.
The owner is probably talking about what NotAPreppie described here: the base fuel all comes from the same place, but the additives are different and brand-specific. So I wouldn't be surprised if they got their deliveries from the same trucking companies, which brought fuel from the same depots, etc. I WOULD be surprised if it were "the same fuel".
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Old 10-14-2018, 09:25 AM
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The RVP thing makes sense. However, the first time I heard about summer/winter levels of ethanol was from the mechanic who works on my chainsaw. He advised to buy my premium gas for it in the summer. Also a couple of months ago, the news was reporting a ramp up of ethanol in preparation for winter which seems to confirm the levels differ during the year.

In CO it is hard to find a gas station that supposedly doesn't use ethanol. We are at an elevation of 6000 + feet. Unlike lower elevations, our gas octane ranges from 85 to 91. The Mercedes CLK that I lost in a hailstorm in June prior to my RX8, was supposedly to have a significant performance boost at lower elevations according to the dealer.
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Old 10-14-2018, 09:42 AM
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Regarding the Shell/Exxon Mobil thing, I was under the impression that the companies are now one. If true, it is possible they have standardized the blends. Personally I have found with Shell premium, I get worse gas mileage than with other premium gas. I can say however, there seems to be a very slight enhancement to my performance. Believe it or not, using premium gas from Safeway supermarkets, my gas mileage improves a little. My best gas mileage and performance comes from a gas station called Corner Store which seems to be a franchise in this area. I think they may be part of Valero. There is a sticker on their pumps that say Top Teir Gas. I have not tried Exxon/Mobil yet, but plan to.

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Old 10-14-2018, 03:03 PM
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Originally Posted by Petscar View Post
The RVP thing makes sense. However, the first time I heard about summer/winter levels of ethanol was from the mechanic who works on my chainsaw. He advised to buy my premium gas for it in the summer. Also a couple of months ago, the news was reporting a ramp up of ethanol in preparation for winter which seems to confirm the levels differ during the year.

In CO it is hard to find a gas station that supposedly doesn't use ethanol. We are at an elevation of 6000 + feet. Unlike lower elevations, our gas octane ranges from 85 to 91. The Mercedes CLK that I lost in a hailstorm in June prior to my RX8, was supposedly to have a significant performance boost at lower elevations according to the dealer.
If you don't want gasohol, here is a link you can use:

https://www.pure-gas.org

Any car will have better performance at lower elevation, especially a naturally aspirated car. Denser air means you can create a bigger boom for more power.

When I was in Costa Rica with a Suzuki Jimny(80 BHP), I was climbing the mountain roads and it eventually actually got so bad that I was forced to stay in 2nd gear and keep the RPM high - otherwise the car just has not enough power to climb.
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Old 10-14-2018, 04:08 PM
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Thanks Jinx. 4 stations in Colorado Springs. Awesome.
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Old 10-14-2018, 10:27 PM
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In Minnesota where I used to live the MN Street Road Association kept a detailed list of non-ethanol stations. We frequented them for our motorcycles and said thanks each time we used those stations. That network/support worked great and most every station stayed in the network had at least 1 tank (93 or 91 octane) with no ethanol. I wish other states organizations did the same. http://msra.com/wp-content/uploads/2...18-Non-oxy.pdf

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Old 10-15-2018, 08:41 PM
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I was an Exxon fuel distributor in West Texas, and our refinery was an old Shell refinery.

Before there were federal standards in the 90's, the gas had lots of butane which cause our fuel pumps at stations to vapor lock on hot days.

My Ford f150 would quit idling sometimes, and I'd put in a bottle of Techron to smooth idle.

At a oil school in 1985 Exxon said Techron was good even though from Chevron.

It's still good so go to Chevron or Texaco for that fuel.

Many fuel outlets have interchange agreements where they trade gas except in the Golden triangle of Texas, Houston ,DFW, Austin, and San Antone which all have pipelines.

When a hurricane made premium short last year all over Texas, I went to Sam's club, and don't seem to have trouble.

I have spare bottle of Techron hanging if I do.
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Old 10-15-2018, 11:14 PM
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I wish there were Chevron stations near where I live. :/
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Old 10-16-2018, 12:17 AM
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I consistently get near or slightly above 300 miles per tank on 13.5 gallon fill of Shell 89 or greater octane (not just 93 octane) in Michigan.

Any other gas, including top tier rated Chevron, or Costco (yep, Costco is rated as top tier, as are about 5 others), and I get between 270 and 280 miles on same 13.5 gallon fill, with approx same 40% highway/60% city driving.

It's been this way since day 1.

Now that Shell - at least in Michigan - is hardly any more expensive, and often the same price, than most other branded gasoline (except Costco and Sam's Club) - I find myself using Shell far more often.

I'm not sure of the reason for his mileage increase, but speculate that Shell really does do a better job with formulation, and that this mitigated the standard E10 crap that's become the norm here, at least in Michigan (going to E15 as standard gasoline is idiotic, as now being proposed).

I don't like ethanol for many reasons, and the major automakers are really opposed to it for good reason (their vehicles produced prior to 2012 and even some current models have been proven to be adversely effective by 15% or higher levels of corn alcohol level gasoline based on methodical and rigorous internal testing - it has adverse effects on many fuel system components and materials that are used in those components, among other things).

Subsidizing the corn belt farmers in order to achieve higher forced levels of ethanol mandated at gasoline pumps is IDIOTIC policy; it takes 100 gallons of water to grow a bushel of corn, not to mention massive quantities of pesticides and phosphate-based fertilizers, yet ethanol is hydrophilic and yields significantly less energy when combusted than pure gasoline.
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Old 10-16-2018, 02:15 AM
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Originally Posted by IamFodi View Post
I wish there were Chevron stations near where I live. :/
I have two near my house.

I have tried Chevron 94 and discovered there is not really any different in fuel mileage. I still get pretty crappy mileage with my Osmium(which is even denser than Lead) foot.

I don't think the stock map is designed to take advantage of the higher octane, either.

Originally Posted by RotoRocket View Post
I consistently get near or slightly above 300 miles per tank on 13.5 gallon fill of Shell 89 or greater octane (not just 93 octane) in Michigan.

Any other gas, including top tier rated Chevron, or Costco (yep, Costco is rated as top tier, as are about 5 others), and I get between 270 and 280 miles on same 13.5 gallon fill, with approx same 40% highway/60% city driving.

It's been this way since day 1.

Now that Shell - at least in Michigan - is hardly any more expensive, and often the same price, than most other branded gasoline (except Costco and Sam's Club) - I find myself using Shell far more often.

I'm not sure of the reason for his mileage increase, but speculate that Shell really does do a better job with formulation, and that this mitigated the standard E10 crap that's become the norm here, at least in Michigan (going to E15 as standard gasoline is idiotic, as now being proposed).

I don't like ethanol for many reasons, and the major automakers are really opposed to it for good reason (their vehicles produced prior to 2012 and even some current models have been proven to be adversely effective by 15% or higher levels of corn alcohol level gasoline based on methodical and rigorous internal testing - it has adverse effects on many fuel system components and materials that are used in those components, among other things).

Subsidizing the corn belt farmers in order to achieve higher forced levels of ethanol mandated at gasoline pumps is IDIOTIC policy; it takes 100 gallons of water to grow a bushel of corn, not to mention massive quantities of pesticides and phosphate-based fertilizers, yet ethanol is hydrophilic and yields significantly less energy when combusted than pure gasoline.
How do you do 300 miles a tank? Your gas mileage is better than what I could get in my old V6 Accord, which is supposed to be more fuel efficient.

Standardizing E15 will have consequences. This needs to be stopped as most cars aren't designed to take E15. E10 is the maximum.
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