Ok so my wife and I will be picking up our new GLC sometime in the next 5-7 days and wanted to know what type of gas the car REALLY takes. Reason why I am asking is that the Sticker say Premium but when I was looking I have heard from the sales people that they said Regular or middle grade gas works fine with no issues. Now I know they are looking to sell a car and they won't be responsible if something happens so what does actual owners use?

 

I think the best thing to do, is when you get the car look in the owners manual and on the gas cap door and see what the manufacturer says and then decide which direction you want to go. There is A LOT of discussion on which grade of fuel to use.

 

Our manual states Premium. Your getting 241 hp out of a 2.0 liter turboed 4 banger engine.

 

This GLC300 owner uses premium. Like it was said above, to get this kind of performance from a 2.0 liter 4 cylinder engine something has to be sacrificed. The manufacturer also wants to sell cars so if a lesser fuel was ok don't you think they would say so ...

 

Don't pay attention to the so called experts. Bad advice.

Follow the guidance in the Operator's Manual.

I use 93 octane Top Tier fuel exclusively.

Will the vehicle run on 87/89 octane fuel? Of course it will. Will it run well? NO!

As mikebar2 stated, we are talking about a 241 horsepower two liter turbo charged four cylinder direct injected engine. That is a lot of horsepower for a small engine. One of the reasons the engine develops such stout horsepower is the requirement to burn 91/93 octane fuel.

Additionally, and perhaps most importantly, using unapproved fuel will most likely void your warranty.

 

+1
Contrary to popular belief, higher octane fuel is actually requires more compression than lower octane to detonate which is why it's used in higher performance engines as it mitigates premature detonation that can and will damage the engine over time. This is generally observed as "knocking" in the engine. Don't buy an expensive car and cheap out on gas

 

If your going to cheap out on fuel you might as well go all the way and use the cheapest oil that you can find. If you research you may find some paraffin based oil for a buck a quart.

 

Thanks I was planning on putting the high octane fuel but I wanted to make sure. Kind of sad that these dealers miss lead people into thinking that using middle grade fuel is ok on their own cars when obviously it impacts performance which you are paying for in the first place.

 

at the end of the day only put premium if you have the option but if you are in a pinch lower grade petrol will be fine to get you to the next gas station.

 

Don't these engines have knock sensors - if you use a lower octane fuel the computer dials the advance back - so you lose power and mileage. Not a good tradeoff IMO but would it damage the engine? I don't think so.

 

Regarding LOWER OCTANES and according to German industry experts from Mercedes, BMW, and Porsche:
Lose power? Yes, somewhat.
Lower mpg? No.
Damage engine? No.

 

Call me Thomas, but you're saying that one can use midgrade and only lose some power, yet maintain MPG? (no idea on engine damage for me.)

I've used mid grade on my Acura, and Audi, and did indeed see a MPG drop. It wasN'T enough on the Acura, that it didn't pay to use the lower grade. I'm still trying to determine the drop for the Audi- though I suspect I'll continue to burn premium. (that may change if this price differential keeps widening. I'm routinely seeing 50 cents a gallon difference, but I've seen 60 cents popping up here and there.)

As for Benz, they were the only brand of these three that implied that one should use premium... period. For my Acura and Audi, it stated that it is ok to use lower grades, but some sacrifice would be made.

So I'm wondering if Benz put enough programming to adjust the timing when using a lower grade. Even the manual discourages the use of NON-premium grade gas.

And here's hoping that we don't get a bunch of comments about "if you can afford a premium car......."

 

Yes, these cars have knock sensors. Burn what fuel you like. MB recommends premium.

 

I appreciate everyone's opinion on this post - from the flip/dealer side - from my side with over 685 personal customers on the road at this moment..

1) Premium is recommended - and will give you best fuel economy - in line with EPA ratings - and in practice "most" customers on a MB get a bit better than EPA with overall conservative drive styles - and/or using the fuel economy "education assistant" in the cluster to adjust driving habits to maximize fuel economy.

2) Mid=grade is OK - without knocking/abnormal behavior - however with mid-grade "about" 50% of the dollar savings will be lost to lower fuel economy. So - a 10cent/gallon savings at the pump - accounting for lower MPG - "might" result is a actual 5cent savings - if differential between Premium and Mid-Grade is $1.00 gal - actual savings accounting for lower MPG will be $.50 per gallon

3) I have never had a customer yet with problems specific to mid-grade - however there are customers who have had problems with either "bad gas" - or long storage

4) With the ethanol component - for my customers I recommend a 1/2 bottle treatment Stabil Marine Fuel Stabilizer as preventative to clean up the ethanol/water horse sh*t every 6mo to one yr.

5) It's Diesel - such problems there - really - with such a wide/wide variance in diesel quality - some states up to 20% unregulated bio mix - a whole different kettle of fish

Keep the beat !

 

Actually, I'm not saying it personally, but German auto industry experts were quoted in a NYT article as having said that. However, my experience since 1992 driving 91-octane-recommended Benzes is in line with that statement in that no appreciable mpg drop occurred for me from 91 to 89 octane. I didn't notice a power drop either, but that's tough to measure by subjectively.

BMW used to say (maybe still does) that 89 is an acceptable substitute for 91 in the USA.

I'd be the last to say, if you can afford a premium car... But, if you have money to burn (literally)...

 

Thanks -- good info based on solid experience. I researched this topic a few years ago and recall a Porsche engineer stating that a loss of power in going from 91 to 87 octane amounts to something just less than 2% with no measurable effect on mpg and emissions. Broadly applying that info (unscientifically, of course) for the GLC that's less than 5 HP. I'm not in favor of 87 octane, but 89 might deserve consideration.

 

So, it looks like the experts are in the camp that using mid grade would reduce HP a bit but little other impacts. Hmmm, so maybe it is worth saving 10% or more in fuel costs to use a lower grade fuel. I may go that dark side a bit after my break-in period is through.

 

Your car your decision. Penny smart, pound foolish.

 

Uh, okay, why do you say that in light of the above comments?

 

Just saying believe what you want and do what you think is best for your car since it is yours.

 

No, you said more than that. I realize that the manual does indeed state to use premium gas, and I was planning on doing so. However, there are a few quotes, that although may be hearsay, do discuss the impact, of using lower octane fuel.

The posts supporting the use of premium essentially call out engine size, but really don't discuss how using lower octane would impact an engine. Octane ratings, for the most part, impact the knocking that would go on in an engine. With computers in place, the knocking is eliminated and some brands use the same engine in multiple vehicles and suggest using premium in one model and regular in another model (Honda is one for example.) So it's reasonable to explore fuel options and not pigeon hole one as being cheap and uninformed for asking. AND they also indicate using lower octane fuels do not harm the engine. Not sure why it would in a Benz.

 

For what ever you want to make an issue of something that is your choice and convince others that your right. As I stated before, do what's right for you.

 

Ok, I have used both 87 and 91 (USA) and hence can give real world information. I cant comment on effect on engine in long term, but "experts" have suggested it should not matter.

MPG: No big impact. If you drive more than 70% on freeways during your commute, by all means go for 87 from mpg POV. City driving takes a 1-2 mpg hit as higher RPMs are hit often, so try not to be a lead foot. I drive on ECO and Normal mostly and use Sport for merging/overtaking.
POWER: I hope you are not buying GLC to drag race. For almost all of the use cases you will be happy with either 87 or 91. I have never felt issues with merging, passing and occassional flooring.

What MPG do I get?
I commute 35 miles one way everyday. I get ~29mpg using 91 and ~28.5 using 87. I drive using Distronic almost entirely. I did notice that safeway 87 was worst with mpg dropping to even 27 on one instance, so please try to get Shell or Chevron.

Do I always get 87?
No.

Is it economical to run 87?
Yes in my case.

Have I experienced knocking when using 87?
No

 

I guess the big ? In my mind is, let's just say you have an engine performance problem, take it in to the dealer and they determine it's a burned valve caused by knock. They check the fuel and find 87 octane. Can they deny the warranty? I don't need speculation or what you think. Legally are they on solid ground? If on minimally shakey ground it seems that the deep pockets usually wins. JMHO.

 

I've discovered way back in 1992 -- my first 91-octane M-B, before that diesels -- that 89 produced no adverse symptoms in terms of mpg, power, and engine longevity. I ran a 2004 C-Class 4Matic wagon for 9 years on 89 and never had a mechanic touch the engine, except for oil changes. When I traded the wagon, it used no oil between changes and never knocked. After 24 years is my luck about to run out, I don't think so.