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  • General Discussions about the 300M
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General Discussions about the 300M

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User avatar
 #332651  by protoadies
 May 29th, 2014, 6:03 pm
I never had a vehicle that required anything other than cheapest unleaded. So I would go to whom ever was cheapest.... Now with my special I'm using Wal-Mart's mid grade gas and I was averaging 13.5 mixed mpg. I put in Exxon's supreme gas today and noticed my mpg went up to 17 mixed driving. What is everyone else using
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 #332654  by Chrysler1924
 May 29th, 2014, 6:47 pm
I may be wrong here, but that mileage seems awfully low, even if you were running regular. I get noticeably better mileage with 91 Octane than I do with 87, but some folks here don't notice a difference.
User avatar
 #332656  by LUNAT1C
 May 29th, 2014, 6:49 pm
I stick to Shell 89. 91 has zero positive effect.
User avatar
 #332662  by M-Pressive
 May 29th, 2014, 8:11 pm
Hess or whatever is cheaper. 87 all the way.
User avatar
 #332667  by FIREM
 May 29th, 2014, 8:39 pm
What ever is cheapest when I need gas.
Bet you increase in mileage is more related to your habits rather than grade of gas.
User avatar
 #332669  by Mottman
 May 29th, 2014, 8:43 pm
I usually gas up on payday at my local Citgo. Most of the time I just use regular.
Whenever I can, I will go for mid-grade. The last time I bought Hi-test about a
year ago, The EVIL Sickness pinged like hell ! There are a few possibilities for that
( 1 ) The gas station got a bad truckload of fuel.
( 2 ) At the time, gas prices were really high. Regular was just under $4.00 per gallon.
And super was almost $4.25 a gallon. I can easily believe the station was not selling
much Hi-Test, and it was going stale in the ground
( one of the biggest downsides of 10% ethanol gas ).

The absolute worst gas I have used so far was WAWA regular unleaded 87 octaine.
( I was seriously about to drop the tank to get that sh@t outta there ! )
Took 2 fillups of mid grade to finally clear up the pinging ! The best fuel you can
use is any grade WITHOUT ETHANOL ! If you can get it.
Keep in mind I work for Altaquip,
We service all the small engine products for Lowes and Sears.
Our shop alone averages over 200 pieces a day.
95% of the engine issues are bad ETHANOL fuel.
This shop alone, ships out over 400 gallons of waste/stale fuel every week !

10% ethanol gas has been proven to knock down mpgs and power.
And it will carbon up your engine and cause all sorts of problems.
This is why you read alot about people using Seafoam to decarbonize theyr engine(s).
User avatar
 #332676  by adu1982
 May 29th, 2014, 9:47 pm
87 always....tried other but never seen a difference.

The lhs gets 28 mpg on highway at 65-70 with 87..... I never tried to see if it would get much better with 91..... or is just placebo effect.
User avatar
 #332689  by tafi300M
 May 30th, 2014, 1:40 am
So I guess cheap 85 is outa question, which you can get in here? Its just tempting because it's like 30% cheaper than my E95. It contains 80-85% ethanol,tho...
http://www.exxon.com/ethanol
 #332704  by JTROANOKE
 May 30th, 2014, 7:03 am
Mottman wrote:I usually gas up on payday at my local Citgo. Most of the time I just use regular.
Whenever I can, I will go for mid-grade. The last time I bought Hi-test about a
year ago, The EVIL Sickness pinged like hell ! There are a few possibilities for that
( 1 ) The gas station got a bad truckload of fuel.
( 2 ) At the time, gas prices were really high. Regular was just under $4.00 per gallon.
And super was almost $4.25 a gallon. I can easily believe the station was not selling
much Hi-Test, and it was going stale in the ground
( one of the biggest downsides of 10% ethanol gas ).

The absolute worst gas I have used so far was WAWA regular unleaded 87 octaine.
( I was seriously about to drop the tank to get that sh@t outta there ! )
Took 2 fillups of mid grade to finally clear up the pinging ! The best fuel you can
use is any grade WITHOUT ETHANOL ! If you can get it.
Keep in mind I work for Altaquip,
We service all the small engine products for Lowes and Sears.
Our shop alone averages over 200 pieces a day.
95% of the engine issues are bad ETHANOL fuel.
This shop alone, ships out over 400 gallons of waste/stale fuel every week !

10% ethanol gas has been proven to knock down mpgs and power.
And it will carbon up your engine and cause all sorts of problems.
This is why you read alot about people using Seafoam to decarbonize theyr engine(s).
I think the issues with ethanol in modern automobiles are exaggerated. I don't think the 10% ethanol poses any issues for modern cars that are driven regularly.

The small engine issues are usually caused by people who leave gas in them or in a can for extended periods of time, like over the winter. Amazing that the small engine manufacturers haven't caught on with proper seals and gaskets, since 10% ethanol has been the norm (at least in the southeast) for 20 years. The ethanol blends don't take well to standing. I have not had a fuel related problem or replaced a fuel pump on an automobile, since the days of carburetors. But my cars don't sit. Only fuel related problems have been with small equipment that had fuel left in it over the winter. Typical homeowners that own a chain saw for instance, take it down once a year, limb a couple of trees, and put it back in the garage full of fuel for a year till they need it again.
Alcohol has slightly less energy content than gasoline, hence the slight reduction in mileage. It has an affinity for water, which is not an issue on regularly used automobiles, since they don't develop a lot of condensation in the tanks. The manufacturers modified most seals years ago to resist alcohol blends as they don't like paying warranty claims. As long as you buy from busy stations, where the gas hasn't been sitting a while, alcohol is usually not an issue. Probably more of an issue if a car sits on a used car lot for 6 months with almost empty tank, but otherwise not.
 #332708  by otto95
 May 30th, 2014, 8:17 am
89 octane for the base model, 91 for the Special.

My commute/around town mileage ranges from 22-25 mpg (I live out in the country, so I have alot of steady 45-60 mph stretches on cruise control).

I noticed a long time ago (in a '96 Intrepid) that, to me, the base 3.5 runs alot better on mid-grade 89 fuel. I don't mind the extra $1.20 to $1.50 per fill-up, especially when I put my right foot into it to pass on a 2 lane road...
User avatar
 #332709  by LUNAT1C
 May 30th, 2014, 8:29 am
Personally I can't run 87 in my Special. I get a noticeable amount of knock if I do.
User avatar
 #332713  by Chrysler1924
 May 30th, 2014, 9:28 am
Regionally it's different. Here in Colorado, Regular is 85 Octane as opposed to being 87 Octane on the east coast. So for me, 91 Octane is Premium here in Colorado, where it would usually only be Midgrade elsewhere.

My 300M gets terrible mileage with 85 Octane fuel and I seem to get pinging when I run it. Before I moved to Colorado I pumped Midgrade 91 Octane and got significantly better mileage so that's what I decided to stick with personally.
User avatar
 #332718  by ks4ua
 May 30th, 2014, 11:07 am
I run cheap 87 octane gas with 10% ethanol year round.

My 2004 300M base, gets about 18 in town and 25-26 on the highway. When the AC isn't running a lot (late fall through early spring), I can get 20 in town and up to 27 on the highway (rarely).
Mottman wrote:...The best fuel you can use is any grade WITHOUT ETHANOL ! If you can get it.
...
- "All things being equal" (which they rarely are), our cars should run the best on 100% gasoline as far as mileage goes. But, as Mottman said, it's hard to find 100% petrol any more. There was one station here in town who used to advertise it, but they've apparently switched to 10% ethanol over the last couple of years.

- Technically speaking, good-grade gasoline with a ethanol 10% content should give you a bit more HP and a bit worse mileage than 100% petrol, because that's how corn-based alcohol works compared to petroleum-based gas. (It's the "BTU thermal efficiency per volume"...or something like that.)

- If we ran 100% ethanol (which our system is not designed for), I think we would have about 30% more HP and 30% worse mileage on average. Again that is a ballpark estimate, working from my middle-aged memory. (I've seen the math and some tech articles behind that claim and it seems to work out in real-life assuming that the fuel you get is high-quality.)

- Down in Brazil they have multi-fuel cars, by law, that can run on 100% petrol or 100% ethanol. They can switch back and forth, depending on what is available. I think the cars down there can even now can automatically sense the fuel blend and switch without driver intervention. It used to require a manual switch over.

- Here, the Feds were pushing programs that gave rise to the "Flex Fuel" cars that can run on up to 85% Ethanol, but I don't know how well they work on the E85 stuff.