Just wondering, many experts say most engines do not require premium fuel.

Yes I use premium fuel

I use ethanol free unleaded in the recommended grade. The ethanol free costs a fortune but I only drive 7000 miles per year so the price isn't a problem for me. I believe that a car runs best on the proper grade of fuel, obtained from a top-tier certified brand. My Subaru Forester XT runs great on it.

The car is designed and tested to run best a certain grade of fuel and it seems foolish to second guess that recommendation.

I don't disrespect those who choose to run other grades of fuel and lower quality fuels. But it's so easy to simply do what the manual recommends. It's reallu a personal a choice to do otherwise.

Does it really make a measurable difference if you run regular unleaded from the local Stop n Rob station? Maybe not. I'm not an expert in that. But for me perosonally I always run the recommended grade of fuel. No premium in regular cars and no regular in premium cars. YMMV

yes, i have always followed manufacturer's recommendation on fuel type.

i will admit in other vehicles i have owned i have tried regular grade for a few fill-ups here and with no adverse affect - though i thought the fuel economy may have dipped maybe 1 mpg, but really hard to confirm as the driving done in a week will vary

im sure the benz will undergo that same test as well when its older

one day perhaps i will wise up and buy a car that uses regular fuel

I always follow the guidance in the Operator's Manual. And in the case of the GLC the placard on the inside of the fuel filler door.

MB makes no extra money by you using premium. The rated horsepower and performance of the engine is based on the use of premium fuel. If your spending the money for a Mercedes and can't afford the extra dime for premium you should either get another job or trade it in on a Kia.

If you want performance comparable to the advertised values you should use the recommended fuel type. If you choose to use a lower grade fuel, the knock sensors on your engine will recognize detonation (if you accelerate hard)and retard your timing to prevent engine damage. The resultant will be a decrease in power. The only time I would use a lower octane rating would be if I were running low on fuel & couldn't find hi test.

91 chevron and a cup of Seattles best dark coffee.

Shell gasoline... sometimes 89 (mid-grade) and sometimes 93 (premium). Interesting how Chevron has 91 and Shell doesn't.

I haven't seen 93 octane in years where we are in the Riverside area.

will the lower octane gas be bad for the engine or just affect performance?

91 or 93 octane only for my coupe

Extra dime? Where? It's 30 cents more per gallon than mid and 60-70 more than reg. That's over 10%. Even on these boards, if there was a trick to improve gas milage by 10%, many would be all over it. Yet if one can reduce fuel costs by that, people rip on them? Uh, OK.


I do put only premium in mine, but I do put mid in my Audi as the manual indicates that no harm will result.
MB is silent on this point and since I don't put all that many miles on the Benz, I pony up for premium.

And for any poster that rips on a MB owner for being frugal, many of us can afford the MB due to ones frugal style along ones life.

Amen. Because i was frugal and now in retirement i can afford almost any car i want, but this will be my only car so i don't want to buy premium if it does not matter. When i had a Lexus it said to use premium and i used the mid grade. Noticed no difference. Thank you for all your comments, i think the consensus is use premium.

The fuel cap sticker says only 98 ROM fuel only. All of our gas stations 'normal' and 'premium' are 98 RON only.

Fuel for thought: Having driven in 15 countries around the world, I find that an understanding of octane ratings vs. engine requirements is never absolute. Indeed Mercedes vehicles are sold worldwide including nations like China and India where premium fuel, as we know it in the US, is widely unavailable.

For example, in India a GLC can be purchased with the same engine we have in the USA (4-cylinder turbo gas, 9.8:1 comp ratio, same ECU) yet in India both regular and premium gasolines are 91 RON (our 87 AKI). The “premium” branded gasolines are regular fuels with additives that do not change the octane but provide injector detergents. In limited metro areas of India, so-called “speed” petrols are available with higher octanes derived from octane boosting additives -- the types of additives that are expressly not recommended by M-B, at least in the US. By 2020 and in addition to 91 RON gasoline, India is expected to have 95 RON (our 91 AKI) gasoline available in limited market areas.

In some less developed regions of the world many luxury car owners use normal unleaded gasoline (our 87 octane) and, if available, periodically fill up with the “premium” branded gasoline (same octane with additives) to clean the injectors – a practice in compliance with various MB new car warranties outside the US. Of course, as required by EPA, all USA gasolines over the entire octane range have these detergents added in one form or another depending on the brand.

In S. Ca. premium as a rule is 10 cents higher than mid grade and mid grade is 10 cents higher than regular. And I thought we were getting ripped off. You guys are taking it in the shorts.

They more than likely don't have to meet the emissions standards of the western world and thusly the engines could have a totally different tuning strategy.

We used to be a dime.. then it went to 15... now it's 30... What the heck? So yeah, Prem is usually 60 cents more than reg..... sometimes more, depending upon the brand. Shell especially.

Agree. As we know, engine tuning (or calibration of ECU parameters) determines the amount of fuel to inject based on readings from a large number of sensors in order to optimize engine power output in compliance with applicable emission and fuel economy standards.

The USA version of the GLC is “detuned” as compared with, say, India’s version – a GLC with 3% more power output. Presumably, this slight power reduction results from the USA version of the GLC operating in an environment with more stringent emission standards than those of India. According to a study done by the AAA, lower octanes do not produce more harmful emissions. The level and quality of detergents in the fuel are the factors that play a major role in reducing emissions.

I always use the highest grade attainable

Smart move in my opinion.

+1

I'm not so sure about that. There was a discussion about this here not all that long ago, and I did a little research and came to the opposite view. My understanding is that petrol (gas) with a higher octane rating is required in engines with higher compression ratings to prevent detonation. The manufacturer will tell you what the minimum rating for your vehicle is in your country. There are plenty of articles around that demonstrate that there are no benefits from using a higher octane rating than that. There's still no detonation, there's no better performance or economy, and there's no evidence that it keeps you engine 'cleaner', despite the advertising of the fuel companies. I found one test that concluded that in fact there was a higher proportion of unburnt hydrocarbons in the exhaust emissions from using a a higher octane rating than needed.

My conclusion is that at best you're wasting your money and at worst you may be polluting a little more. If anyone has any evidence to contradict this I'd like to read it.

The problem in my city is that it's easy to find the highest octane rating 98 (US 93), and no so easy to find the next rating down 95 (US 90), when a lot of cars including our B200 only require 95. 98 from Costco is usually cheaper than 95 from a service (gas) station, if you can find it.

You are correct. Fuel sellers "imply" that higher octane is better, but in reality only in terms of antiknock properties. The fuel additive packages are otherwise the same for the different rated fuels. Most folks don't know that the mid grade fuel is actually a blend of regular and premium done at the pump. There is no 3rd storage tank. You are blowing money using a higher octane than needed. You can use lower octane fuel and the antiknock sensors in the engine will retard timing so that no damage is done. You will get lower performance and mileage as a result.