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Discussion Starter #1
I know the manual says that 91 octane is recommended but not required. My salesman said that for the Metris the dealership bought for errands around town, they planned to put in premium (93 octane) throughout the break in period and then switch to regular, checking during both periods to find out what the change in mileage with regular would be. I haven't needed to fill my tank yet (mainly waiting for a camper build that is scheduled to start in a week or two). So I was wondering what other Metris owners are doing. Care to share your experiences?
 

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Generally the highest I can find, 91/92/93. I used to be a strictly Hess guy, I've been upset since they left the market.

An experiment I ran with Sunoco 91 vs 93 showed more improvement in mileage than increase in price. I'd think that would be the case with an advanced design DI Turbo like the M274 which could make use of the increased ignition retardation.
 

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so tell us about the camper build PLEASE. Waiting on my Metris cargo van which hopefully will be here in the next two weeks. I've been drawing plans all winter for what I hope to do to it.
 

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Discussion Starter #4
OK, but I'll put it on a different thread. Look in anyone else interested . . . soon.
 

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Been using 93 as the options around here are usually just 87/89/93 unless I go to Sunoco.

I have a VW Eurovan which also came with recommendation to use 91 or higher. I experimented a few times with lower octane in the VW but found economy suffered, so in the end, there was no real point to using the lower octane. Have not experimented with the Metris yet as I am still breaking it in.it
 

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Discussion Starter #7
Just completed a 3000+ mile trip from NC to Colorado, Wyoming and especially the Black Hills of South Dakota. Bought premium gas on the way out and 87 octane on way back. Mileage out was 24.2 mpg. Mileage back was 25.7 mpg. My better mileage on 87 octane gas might in part be due to driving with the winds rather than against them (it was really windy for part of the trip), a higher percentage of fill ups on the way out had 10% alcohol (which has less energy per gallon), a bit more city driving (I gave talks at 2 universities on my way out - though Manhattan Kansas doesn't involve much city driving), and some slow driving around buffalo herds. Most of the time we drove with the setting on E (economy) rather than the default C (comfort) - though I did like driving in C better.

My bottom line: in my area, premium gas costs 20% more than regular and I clearly did not see 20% better gas mileage with premium (93 in the east though 91 was readily available farther west) even when that tank was used just for highway driving. So I'm planning on sticking with 87 octane.
 

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On my B200T 91 Shell V-Power nets me the best mpg and power delivery. Worst fuels were the "up to 10%" ethanol fuels.

I always use what is recommended. If I need to floor it for a quick pass the 87 will feel out of breath compared to 91. 87 can be used, but you will shirt changed yourself for performance.
 

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Just completed a 3000+ mile trip from NC to Colorado, Wyoming and especially the Black Hills of South Dakota. Bought premium gas on the way out and 87 octane on way back. Mileage out was 24.2 mpg. Mileage back was 25.7 mpg. My better mileage on 87 octane gas might in part be due to driving with the winds rather than against them (it was really windy for part of the trip), a higher percentage of fill ups on the way out had 10% alcohol (which has less energy per gallon), a bit more city driving (I gave talks at 2 universities on my way out - though Manhattan Kansas doesn't involve much city driving), and some slow driving around buffalo herds. Most of the time we drove with the setting on E (economy) rather than the default C (comfort) - though I did like driving in C better.

My bottom line: in my area, premium gas costs 20% more than regular and I clearly did not see 20% better gas mileage with premium (93 in the east though 91 was readily available farther west) even when that tank was used just for highway driving. So I'm planning on sticking with 87 octane.
So have you stuck with 87? I live in South of Charlotte NC and routinely drive across the stateline to SC for fill ups. Reg-to-Premo price diff has crept up to 26%! SC Premium is 1cent difference from the local NC Sam's Club gas price. I done some Reg fill ups and honestly couldn't 'feel' or 'see' a noticeable difference between premo. I'm sure 'on paper' or close analysis the difference is there. One thing I think about if future maitenence/repairs. Would using Reg be harmful to the Metris engine longevity with all other things being equal, anyone?
 

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My thoughts:
On the older cars, when they were designed for higher octane but run on regular, "knocking" or pre-ignition would occur and that could do damage. Modem engines compensate for various octanes instantaneously, so no damage occurs. A while back, I read interviews with engineers from a few mfg's and the one from Benz said premium fuel was required and the one from Porsche would not suggest using lower octane fuel in theirs cars but hinted that their cars are sold all over the world with different qualities of fuels and they don't make engine mods for every country.

I think the reason Benz says that 87 can be used is for fleet sales, where the fleets that do their own fueling would need to put in another pump if premium only was required

That being said, I have been using ethanol-free 87-89 octane most of the time in our 2002 e320 since ethanol was mandated and have been in the Metris. I don't put a lot of miles on either of them so my concern with the ethanol is the separation problem. The Metris gets 23-27 mpg.

Performance-wise, we had an Xterra that I ran e0 most of the time but on a trip had to use e10 and the loss of performance was noticeable.
 

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My approach which I established after many years with our 14 year/old Eurovan which is as strong and efficient as day one at 18mpg.

For routine fill ups, my objective is longevity of the engine: I put ethanol-free 91 octane gas from the price club because the price has been consistently 20% more than the lower octane and is ethanol free.

For road trips, my objective is efficiency and range: I will fill with the higher octane and will put this regardless of cost in this scenario.

If I am away from home, my objective is economy: I will choose the gas that costs within 15% of the 87 octane. Above that percentage differential, there is diminishing return on mpg. The van achieves 25-27mpg but if it would stop resetting default to C instead of E, I bet the mpg could be higher.

I like local chain farm/tractor/fleet gas stations because they seem to have the ethanol free more often, prices are cheaper than the big brands and they have the automated air pumps. I don't like the small corner gas stations because the prices are usually higher than the others.
 

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I can't speak to octane. I use premium (as recommended) regardless of price. Whatever octane you use make sure it's a " Top Tier" gasoline (as recommended). I believe that's more important.

Over the past 20 years, engines have become far more precise, operating under tighter tolerances and at higher compression ratios, while targeting cleaner emissions and improved fuel economy. To achieve these goals, eight automakers—Audi, BMW, Fiat Chrysler Automobiles, General Motors, Honda, Mercedes-Benz, Toyota, and Volkswagen—have united in support of Top Tier gas, specifically recommending it to their owners with the goal of preserving their engines’ original performance and emissions over time.
https://www.consumerreports.org/car-maintenance/study-shows-top-tier-gasoline-worth-extra-price/
 

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Yup, I use premium.
How much are you saving by going to a lesser octane?
That would be like using a lower grade oil to save money- You might save some cash upfront, but down the road, you will end up paying for it.
B
 

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The right gas ensures proper and efficient operation of the engine and full combustion.

Sir, your posts indicate you like being cheap with your car. If this is so, for your own sanity, drive down to your local Ford dealer and trade your van; you will not have a happy ownership experience if this is how you maintain your cars.
 

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I've never had a vehicle that said Premium Recommended. To me, this means that you can use non-premium if you want, but you don't have to. My other cars have said "Premium fuel only", which is a bit different from what MB is saying. My Mazda Milennia was premium only. If you ran 87, which I had to during one of the Florida hurricanes, you knew the car didn't like. In the Metris, I've been running 87 since I had the vehicle, a little over a year now. No issues to report. Engine performs the same with premium and 87. Dealer specifically said 87 is fine to use so I ran with it.

Moral of the story, run what you want. MB didn't say you shouldn't, just not what they recommend.
 

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Mine is Diesel so I don't really have many choices, but on all my other cars I use premium, I don't even look at the price difference, I just assume that I'm paying a fair price. And knowing what the octane means and how the engines are designed I have no problem doing it


As an experiment I just recently started using 89 on my Mini Cooper S which is leased and is used only for daily commute (less than 25 miles a day) so I haven't really noticed any economies, so I might go back to premium.
 
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