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Octane 91 is it really required?
Hey guys.
Every time I fill up my car I always thought to myself if octane 91 is worth it. My dad who has a W222 S550 always gas 87.... and advise me to do the same but he has enough money to change cars every three years I financed my C300 planning to keep at least 5 years not having that kind of a spare. So I decided to find out. As a note, I've been filling my 2016 C300 with mostly 91 octane or at least octane 89 when I'm on a road trip somewhere that has ridiculous 91 prices (like a dollar more...). So for the three fillups I've filled it with octane 87 to see if there are any issues with it. I've asked my friend who works for Hyundai engineering (Mechanical engineering major) and he told me modern engines should really have no issues at all running lower octane that's why Hyundai only recommends to use premium on their Genesis line up. Even if MB engine say required... he presumed that MB would have a better engine tech than a Hyundai anyways so haha. also as a side note, my dealer told me to put 89 BTW.... and the BMW dealer told me the same when I purchased my BMW 335i long time ago (Traded in for the C300). So yeah here we go. So for the past 1500 miles (4 fill ups) my gas mileage stayed the same 32 on hwy 28 on city... I did 80% floor the car to pass some slowpoke in the hwy using RPM's up to 4 to 5K but occasional. I didn't hear any engine noise whatsoever... no knocking whatever. Didn't really feel any power loss tbh. Additionally, if someone is worried about the long term damage I can't say 100% but to add my point my 2005 ML500 passed down from my dad was gassed 87 for 40K of its life under my dad and the truck still runs like a champ with 180K miles. So here is my conclusion. I would for the sake of it continue to gas octane 91... in So-cal costco the regular gas is really expensive that there is only 20 cent difference. But on some occasions when 91 is either not available or the price per gallon is ridiculously high then I would gas 87 or 89. If anyone here is planning to gas 87 feel free in my opinion the C300 can handle it no problem but try to use whatever MB recommends. Let me know for your opinion guys. |
Originally Posted by fantasy521
(Post 7253885)
Hey guys.
Every time I fill up my car I always thought to myself if octane 91 is worth it. My dad who has a W222 S550 always gas 87.... and advise me to do the same but he has enough money to change cars every three years I financed my C300 planning to keep at least 5 years not having that kind of a spare. So I decided to find out. As a note, I've been filling my 2016 C300 with mostly 91 octane or at least octane 89 when I'm on a road trip somewhere that has ridiculous 91 prices (like a dollar more...). So for the three fillups I've filled it with octane 87 to see if there are any issues with it. I've asked my friend who works for Hyundai engineering (Mechanical engineering major) and he told me modern engines should really have no issues at all running lower octane that's why Hyundai only recommends to use premium on their Genesis line up. Even if MB engine say required... he presumed that MB would have a better engine tech than a Hyundai anyways so haha. also as a side note, my dealer told me to put 89 BTW.... and the BMW dealer told me the same when I purchased my BMW 335i long time ago (Traded in for the C300). So yeah here we go. So for the past 1500 miles (4 fill ups) my gas mileage stayed the same 32 on hwy 28 on city... I did 80% floor the car to pass some slowpoke in the hwy using RPM's up to 4 to 5K but occasional. I didn't hear any engine noise whatsoever... no knocking whatever. Didn't really feel any power loss tbh. Additionally, if someone is worried about the long term damage I can't say 100% but to add my point my 2005 ML500 passed down from my dad was gassed 87 for 40K of its life under my dad and the truck still runs like a champ with 180K miles. So here is my conclusion. I would for the sake of it continue to gas octane 91... in So-cal costco the regular gas is really expensive that there is only 20 cent difference. But on some occasions when 91 is either not available or the price per gallon is ridiculously high then I would gas 87 or 89. If anyone here is planning to gas 87 feel free in my opinion the C300 can handle it no problem but try to use whatever MB recommends. Let me know for your opinion guys. https://cimg4.ibsrv.net/gimg/www.mbw...b933729a38.jpg https://cimg5.ibsrv.net/gimg/www.mbw...1b180d9b6a.jpg |
Lol.
You don't even need to do that. Get a costco rewards card. Costco premium gas is cheaper than any local regular gas station's regular gas by 10-30 even 80 cents (High-End areas) Plus 4% cash back. FYI or have enough money to spend on a new car every three years. |
Can MB void your warranty if a mechanical issue arises and it's attributed to the use of non-premium fuel?
I think the answer to this would be the answer to what type of fuel you use. |
Originally Posted by PeteInGilroy
(Post 7254254)
Can MB void your warranty if a mechanical issue arises and it's attributed to the use of non-premium fuel?
I think the answer to this would be the answer to what type of fuel you use. they really can't tell... but if the engine does breaks down its not really the fault of the gas but something else. Lower octane gas won't damage the engine just lower performance. Also I see you drive a Genesis. So do I... I use regular fuel on my Genesis instead of premium that I use for my Merc. |
We don't have 91 in Texas, only 87,89, 93. I always use 93 on my C450 because.. performance.
However, QT decided to put notice out that it 'might' run out of gas at a 'few' of its stations because of Harvey, which caused a mass panic run to the gas stations here. Unfortunately I had to go because I had less than a quarter tank left and needed to fill up to get to work and back. Waited 45 min... and only had 87 available. So I had to get that and then topped it off with some octane booster to help out. I haven't really 'stepped on it', been driving casually, and no problems whatsoever. Granted, as soon as 93 is available again I will get it, but in the mean time doesn't hurt to use 87 (only option anyways). |
Originally Posted by fantasy521
(Post 7254341)
There is no way that MB would void the warranty because
they really can't tell... but if the engine does breaks down its not really the fault of the gas but something else. Lower octane gas won't damage the engine just lower performance. Also I see you drive a Genesis. So do I... I use regular fuel on my Genesis instead of premium that I use for my Merc. 1 - I have no idea how the W205 computer works, but in other cars I own, there are multiple spark tables that correspond to the different octane detected. It really doesn't detect octane, just engine pings (which the knock sensor will detect before your ears do) and change the spark table. It generally takes several tanks to switch back up to a higher spark table. So, in the case of these others cars, you can see at least what fuel the computer thinks you have in. Again, not sure if MB works the same way, but I wouldn't definitely say the dealer has no way to know. 2 - Lower octane fuel can certainly damage your engine IF the computer can't properly compensate for it or the knock sensor isn't properly detecting it. In most cars that recommend premium fuel, the computer happily changes timing, and off you go with reduced performance (probably not noticeable to most people). However, manufacturer have decided some high performance cars because of compression or forced induction might not compensate properly for low octane, or is leaving too much to the knock sensor. If the sensor and timing tables aren't enough to prevent knock, you can damage the engine. In the case of W205, the manual actually lists different things for the C300 versus the rest of the line. This leads me to believe they feel pretty good about the C300 setup to not really cause damage, but not as good with the others. Here is the language in the manual: ----------------------------- C 300 4MATIC: as a temporary measure, if the recommended fuel is not available, you may also use regular unleaded gasoline with an octane rating of 88 AKI/93 RON. All other models: as a temporary measure, if the recommended fuel is not available, you may also use regular unleaded gasoline with an octane rating of 87 AKI/91 RON. This may reduce engine performance and increase fuel consumption. Avoid driving at full throttle and sudden acceleration. Never refuel using fuel with a lower AKI. ------------------------ Based on this, in seems likely a C300 could live happily ever after on lower octane. However, unlike many cars that just say you can use lower octane at decreased performance, MB specifically calls it out as a temporary measure. So, as DapperStyle said, you should probably cut costs elsewhere and stick with the MB requirements. Particularly if you have a C450/43/63. |
Originally Posted by z28lt1
(Post 7255030)
A couple of notes on this:
1 - I have no idea how the W205 computer works, but in other cars I own, there are multiple spark tables that correspond to the different octane detected. It really doesn't detect octane, just engine pings (which the knock sensor will detect before your ears do) and change the spark table. It generally takes several tanks to switch back up to a higher spark table. So, in the case of these others cars, you can see at least what fuel the computer thinks you have in. Again, not sure if MB works the same way, but I wouldn't definitely say the dealer has no way to know. 2 - Lower octane fuel can certainly damage your engine IF the computer can't properly compensate for it or the knock sensor isn't properly detecting it. In most cars that recommend premium fuel, the computer happily changes timing, and off you go with reduced performance (probably not noticeable to most people). However, manufacturer have decided some high performance cars because of compression or forced induction might not compensate properly for low octane, or is leaving too much to the knock sensor. If the sensor and timing tables aren't enough to prevent knock, you can damage the engine. In the case of W205, the manual actually lists different things for the C300 versus the rest of the line. This leads me to believe they feel pretty good about the C300 setup to not really cause damage, but not as good with the others. Here is the language in the manual: ----------------------------- C 300 4MATIC: as a temporary measure, if the recommended fuel is not available, you may also use regular unleaded gasoline with an octane rating of 88 AKI/93 RON. All other models: as a temporary measure, if the recommended fuel is not available, you may also use regular unleaded gasoline with an octane rating of 87 AKI/91 RON. This may reduce engine performance and increase fuel consumption. Avoid driving at full throttle and sudden acceleration. Never refuel using fuel with a lower AKI. ------------------------ Based on this, in seems likely a C300 could live happily ever after on lower octane. However, unlike many cars that just say you can use lower octane at decreased performance, MB specifically calls it out as a temporary measure. So, as DapperStyle said, you should probably cut costs elsewhere and stick with the MB requirements. Particularly if you have a C450/43/63. I'm going to fuel my C300 with the octane 91 as I have done for the past year of ownership not a big deal especially with costco. But if you have a C400/43 or 63s especially the 63 you really shouldn't consider anything lower than 91. If I had a 63 AMG I wouldn't even consider gas my car with 87 octane and write this post. |
Originally Posted by imj0257
(Post 7254892)
We don't have 91 in Texas, only 87,89, 93. I always use 93 on my C450 because.. performance.
However, QT decided to put notice out that it 'might' run out of gas at a 'few' of its stations because of Harvey, which caused a mass panic run to the gas stations here. Unfortunately I had to go because I had less than a quarter tank left and needed to fill up to get to work and back. Waited 45 min... and only had 87 available. So I had to get that and then topped it off with some octane booster to help out. I haven't really 'stepped on it', been driving casually, and no problems whatsoever. Granted, as soon as 93 is available again I will get it, but in the mean time doesn't hurt to use 87 (only option anyways). even if its a 450... temporary 87 fueling shouldn't damage the engine even if you step on it but try not to. Good Luck! |
This is my personal experience, which might be different from some people.
Before the c400, I've had a few different cars, which one of them was a 2015 genesis coupe ultimate manual. Now, I don't know how the Genesis brand do their things nowadays with recommended fuel things but my genesis coupe was still under the Hyundai group and this is how it was set by Hyundai. You can run any type of grade you'd like because the ECU is fully capable of adjusting everything, not temporarily like how the MB states it but permanently. However, if you run 87 oct, you lose a few hp/tq. There was one time when I had to change cars with my dad for two days and he filled it up with 87 and brought it back to me. When I got the car back, it had full tank but the estimated range was only at 230 miles and that's all I actually got in that tank. I filled it up with 93 oct all the time and always got 300 miles, give or take, whether that was the estimated range or the real driven mileage. Also, as you all know, Infiniti recommends 91 or higher oct for their cars. My friend owned a 2007 g35s sedan for more than 100k miles and ten years and always only ran 89 oct. He doesn't drive/accelerate his car fast at all so maybe that helped it but he didn't have any engine issues. Will I personally run anything lower than 91 in my c400? No because of the performance loss and who knows what else might happen. The gas price difference between regular and premium at where I live (NC) is about 40 cents, give or take so it is a pretty big difference but given the fact that I get more mileage out of a tank running premium, the cost difference after all is not much at all so I don't really see the reason not to run premium. |
In a study that could indicate a need to change how we name fuels, the American Automobile Association (AAA) discovered that using premium fuel (91-93 octane) in a car that only requires regular (87 octane) does absolutely nothing. AAA's experiment looked at whether cars requiring just regular fuel would have an effect on power, fuel economy, and emissions. To do this, they used 2016 models of a V8 Toyota Tundra, V6 Dodge Charger, and 2.0-liter Mazda 3. Each car was put through the EPA's city, highway and aggressive driving loops on a chassis dyno, with only the fuel as a variable. The testers also did horsepower measurements on the dyno. In the end, every aspect remained virtually the same. There were minute changes for some of the vehicles, but they weren't enough to be noticeable. And for fuel economy, the differences wouldn't even come close to the 23-percent increase in fuel cost AAA estimated for premium. AAA director of automotive engineering Greg Brannon said that the cars did recognize and compensate for the different octane fuels. AAA measured ignition timing in each vehicle with each type of fuel, and there was a noticeable change in timing when premium fuel was used. So it was surprising to the testers that none of the vehicles adjusted timing in such a way that would improve at least one performance aspect. In essence, Americans waste $2.1 billion every single year on premium gas that their cars don't need, AAA says. There is one minor caveat to this test though. The only thing tested here was the effect of octane on vehicle performance. While spending more on premium won't get you any benefits, there are differences in fuels, but the differences come from fuel quality, not octane. In a test done by AAA earlier this year, it was discovered that fuel that meets TOP TIER standards for fuel detergents and additives are much better for engines. The test revealed that fuel that only meets government requirements for additives left 19 percent more deposits over 4,000 miles compared with the TOP TIER fuel. If you're interested in which brands sell TOP TIER fuel, you can find the list here. So the takeaway here is buy the fuel the manufacturer recommends, and buy it from a TOP TIER brand. This way you'll save money and keep your car healthy. |
Originally Posted by fantasy521
(Post 7255239)
Like I said.
I'm going to fuel my C300 with the octane 91 as I have done for the past year of ownership not a big deal especially with costco. But if you have a C400/43 or 63s especially the 63 you really shouldn't consider anything lower than 91. If I had a 63 AMG I wouldn't even consider gas my car with 87 octane and write this post. The C400/450/43 - Run 91 or more. Absolutely. Never cheap out on a biturbo V6. (I've personally only ever used 93) If you put less than 91 in a C63 or C63S, please proceed to the nearest Mercedes Benz dealer and take possession of the B Electric. :smash: |
Originally Posted by -=Hot|Ice=-
(Post 7256728)
Also, there is also a difference between "Premium Fuel Recommended" (most cars that request higher Octane) and "Premium Fuel Required". I know earlier in the the thread an Infiniti was mentioned, not sure which model, but most Infinitis only recommend and not require premium. I don't have it any more if my memory servers (and it may not) our Infiniti said "required" on the gas cap but the manual said recommended, and you could use other with reduced performance. The W205 says "required" (although notably different for the C300 versus other variants), which is different than the cars that state regular, or the cars that state "recommended" I'm not saying the car will blow up on 87 Octane. I'm saying it isn't a valid comparison to compare this car with the AAA article, or many other cars that will go fine on lower Octane, because it is fully designed to do so, even if the manufacturer "recommends" premium fuel. |
Straight from the manual. So since I was forced to fill up with 87, it looks to be ok as long as I don't drive crazy.
https://cimg5.ibsrv.net/gimg/www.mbw...0dfdae6c14.jpg |
Originally Posted by imj0257
(Post 7257302)
Straight from the manual. So since I was forced to fill up with 87, it looks to be ok as long as I don't drive crazy.
https://cimg5.ibsrv.net/gimg/www.mbw...0dfdae6c14.jpg Don't worry... |
Originally Posted by DapperStyle
(Post 7253922)
The car just won't perform as well. Turbo engines run best on premium fuel. I think if the extra money spent on 91 is too much I would look to cut costs elsewhere. Maybe buy some off brand breakfast cereals or some generic over the counter medicine/products. You'll recoup the costs quicker that way.
https://cimg4.ibsrv.net/gimg/www.mbw...b933729a38.jpg https://cimg5.ibsrv.net/gimg/www.mbw...1b180d9b6a.jpg Not all engines that are turbocharged require premium fuel. |
Originally Posted by -=Hot|Ice=-
(Post 7262723)
Not all engines that are turbocharged require premium fuel.
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