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  #1  
Old 09-23-2017, 03:57 PM
Rod Rod is offline
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Octane Booster for regular gas?

My wife is on her 3rd Mercedes. The first two were totaled, but not her fault, she walked away safe because it was a Mercedes.

Now she drives a 2003 E320 and since times are getting tough, she wants to save a few dollars and use the mid range or regular sometimes. She thinks it would be OK, but I disagree. She thinks I don't always know it all. (Ha)

So to solve her questions I'm thinking about using reg or midrange gas with an Octane booster, like the Gumout brand. She gets her way and so do I.

It only $2.24 at walmart and would cost half as much a the 93 octane per tank. If Mercedes wants at least 91 octane in the gas we could use a booster with mid-range gas cheaper yet keep the octane up near the suggested rating.

What say You?

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1998 Land Rover Range Rover 66K Miles
1988 300SE Totaled in 1998, hit by drunk driver, but we walked away OK
1989 420SEL 140,000, just warming up. Total by 18 wheel gas truck rear ended, but refused to lose another MB. Had it repaired cost $10,000+ Great Car again SOLD it for a 2003 C320 to save on gas
1991 2500 Suburban 454, 130,000, Best truck in the world. SOLD it out right.
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  #2  
Old 09-23-2017, 04:23 PM
sixto's Avatar
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Surely you can agree on other ways to save $50 a year (10K miles).

Sixto
98 E320s sedan and wagon
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  #3  
Old 09-23-2017, 05:35 PM
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M112 runs fine on 87 octane below ~80f. Above that temp and it starts pulling timing at high load. You're not going to hurt the engine on 87 octane but you will be down on power and fuel economy in hot weather.
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  #4  
Old 09-23-2017, 05:51 PM
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The engine control system will automatically retard the timing to compensate for low octane gas. So you probably won't hurt anything, but your mileage and performance will suffer. Sort of pointless.
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  #5  
Old 09-23-2017, 06:04 PM
Rod Rod is offline
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This is South Louisiana and right now it's 94 in the shade by the temp on the screen porch. It's 30 minutes to the Gulf of Mexico.

Do you think I should use octane booster on fill up even with 87 or 89 at the pumps down here or use 89 most of the time? I don't want an engine issue later.
We bought good stuff when we were working but now we try not to spend any money we don't have to and fuel keeps us moving and active to keep us from the nursing homes.

Retired, every quarter counts.
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1998 Land Rover Range Rover 66K Miles
1988 300SE Totaled in 1998, hit by drunk driver, but we walked away OK
1989 420SEL 140,000, just warming up. Total by 18 wheel gas truck rear ended, but refused to lose another MB. Had it repaired cost $10,000+ Great Car again SOLD it for a 2003 C320 to save on gas
1991 2500 Suburban 454, 130,000, Best truck in the world. SOLD it out right.
1952 8N Tractor 1,000,000-/+
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  #6  
Old 09-23-2017, 06:16 PM
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$50/year for 10K miles in fuel costs is a dinner for two with tip. If times are really that tough, perhaps sell the Mercedes and buy a Yaris?

Not trying to be ugly, but people trying to save pennies of fuel drives me CRAZY. Find something else to cut costs, or just don't drive so much. Pretty simple...
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  #7  
Old 09-23-2017, 06:49 PM
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As others have said, the car will run on regular or mid, and not be harmed but fuel mileage could / would drop off.

My 97 SL320 with a 3.2 L inline 6 has less power on mid grade so premium is required. ( heavy car )

My 97 C280 with the 2.8 L inline 6 ( same basic engine as the 320 ) runs just fine on mid grade however, I've never checked MPG. I keep this car for Mom and Dad so it sees sub 50 MPH round town driving, if it was being run on interstates I'd run on premium as engine load would be much higher.
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  #8  
Old 09-23-2017, 07:24 PM
Rod Rod is offline
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The reason for keeping the Mercedes is for the safety of it because the first two Mercedes saved my wife's life.
The first MB was lost to a driver having a seizure ran a red light and hit her in the passenger side, the police told her at the wreck site she would be dead in any other car. The man driving behind him was doing 70 trying to keep up with him to stop him by honking the horn and warning other drivers.
The second car was lost when a 18 wheeler crushed the back of the car up to the back seat. She was shaken but OK after a trip to the hospital.

So we are trying to keep the MB and save a little money on the gas, that's all.
__________________
1998 Land Rover Range Rover 66K Miles
1988 300SE Totaled in 1998, hit by drunk driver, but we walked away OK
1989 420SEL 140,000, just warming up. Total by 18 wheel gas truck rear ended, but refused to lose another MB. Had it repaired cost $10,000+ Great Car again SOLD it for a 2003 C320 to save on gas
1991 2500 Suburban 454, 130,000, Best truck in the world. SOLD it out right.
1952 8N Tractor 1,000,000-/+
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  #9  
Old 09-23-2017, 07:49 PM
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Quote:
Originally Posted by Rod View Post
This is South Louisiana and right now it's 94 in the shade by the temp on the screen porch. It's 30 minutes to the Gulf of Mexico.

Do you think I should use octane booster on fill up even with 87 or 89 at the pumps down here or use 89 most of the time? I don't want an engine issue later.
We bought good stuff when we were working but now we try not to spend any money we don't have to and fuel keeps us moving and active to keep us from the nursing homes.

Retired, every quarter counts.
In that weather it'll be cheaper to simply use 91+ octane. Once it drops under 80f you can use 87 octane.
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  #10  
Old 09-23-2017, 08:03 PM
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Let's let math do the talking for us. According to the EPA, the combined average fuel economy on premium fuel is 20mpg for your car in automatic form without 4-matic.

Using local pricing, regular gas is $2.55/gal and premium is $2.85/gal

Let's assume you take a 15% fuel economy penalty for switching to regular fuel (retarded timing, greater quantity injected to combat knock, less power, etc). That drops your average fuel economy to 17mpg.

So averaging 20mpg on $2.85 premium fuel gives you 14.25 in fuel per mile.

Averaging 17mpg on $2.55 regular fuel gives you 15 in fuel per mile.

That 3mpg fuel economy difference obviously offsets any "savings" you made at the pump filling up.

In reality, the difference can be much greater than 15% based on the quality of fuel. My Honda (which isn't even designed for premium) will do ~25mpg in city driving, but struggles to even do 20mpg on regular. On the highway it's even bigger of a difference - somewhere around 36mpg on premium vs 28-29mpg on regular.

Sticking regular gas in the tank of a car designed for premium fuel is false economy, it will end up costing you money in lost economy.
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  #11  
Old 09-23-2017, 09:48 PM
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Quote:
Originally Posted by Mxfrank View Post
The engine control system will automatically retard the timing to compensate for low octane gas. So you probably won't hurt anything, but your mileage and performance will suffer. Sort of pointless.
This. Exactly what I was going to say, except with a $.30 per gallon minimum delta between premium and regular these days, you won't lose enough mpg to make premium more economical. Back in the days of a $.15 delta it was a wash.
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  #12  
Old 09-23-2017, 09:50 PM
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Quote:
Originally Posted by Diseasel300 View Post
Let's let math do the talking for us. According to the EPA, the combined average fuel economy on premium fuel is 20mpg for your car in automatic form without 4-matic.

Using local pricing, regular gas is $2.55/gal and premium is $2.85/gal

Let's assume you take a 15% fuel economy penalty for switching to regular fuel (retarded timing, greater quantity injected to combat knock, less power, etc). That drops your average fuel economy to 17mpg.

So averaging 20mpg on $2.85 premium fuel gives you 14.25 in fuel per mile.

Averaging 17mpg on $2.55 regular fuel gives you 15 in fuel per mile.

That 3mpg fuel economy difference obviously offsets any "savings" you made at the pump filling up.

In reality, the difference can be much greater than 15% based on the quality of fuel. My Honda (which isn't even designed for premium) will do ~25mpg in city driving, but struggles to even do 20mpg on regular. On the highway it's even bigger of a difference - somewhere around 36mpg on premium vs 28-29mpg on regular.

Sticking regular gas in the tank of a car designed for premium fuel is false economy, it will end up costing you money in lost economy.
In my experience it won't be a 15% mpg delta. It will only be about 6 or 8%.
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  #13  
Old 09-23-2017, 11:26 PM
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Quote:
Originally Posted by Diseasel300 View Post

In reality, the difference can be much greater than 15% based on the quality of fuel. My Honda (which isn't even designed for premium) will do ~25mpg in city driving, but struggles to even do 20mpg on regular. On the highway it's even bigger of a difference - somewhere around 36mpg on premium vs 28-29mpg on regular.

.
Something else is wrong with your Honda.
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  #14  
Old 09-23-2017, 11:39 PM
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Originally Posted by tjts1 View Post
Something else is wrong with your Honda.
Nothing is wrong with the Honda. The factory sticker claimed 22/32. With the types of roads in this area and the number of hills (a flat road doesn't exist here) no car will ever get it's rated fuel economy.
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  #15  
Old 09-24-2017, 03:57 AM
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Originally Posted by Rod View Post
TThe first MB was lost to a driver having a seizure ran a red light and hit her in the passenger side, the police told her at the wreck site she would be dead in any other car.
A colleague of mine had a very serious accident in a Jaguar. Her and her daughter and the daughter was hospitalised but survived relatively unimpaired.

The Jaguar? A write-off.

She and the police said that, were it not for that car, she would have lost a daughter.

I'm very pro-Mercedes but I'll never understand why she replaced the Jag with a Merc.

Takes all sorts.

RayH

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