Jovsky

This may sound stupid of a question, but I got to ask it anyway since I don't know the answer. I'd like to ask the tech guys whether putting an 87 Octane Rating Fuel in a Mercedes Benz Engine is okay. I know that based on the manual, you should fill her up with Premium Fuel which is 91 Octane Rating.

My question now is: Will it damage the engine if you put in 87 Octane Rating? My friend who happens to be cheap puts in 87 Rating in his 1992 300E and claims it runs just the same. I am not sold by his suggestion since the manual states that you should fill her up with Premium Fuel which is 91 Octane rating. Any advice is mostly appreciated. Thanks guys!

KJI3jflarryfe93

in Sweden the lowest octane is 95, we also have 98 and 99 Shell Formula.
going lower than the recommended 91 isn't very good for the engine in the long run?
87 has a lower energy content, your car gets slower and weaker.
your ignition will adapt to 87 octane if you use it.

old cars without electronic ignition will have pinking noise from the engine if using lower octane than recommended.
they need additives in the tank to grease the valves

if you have electronic ignition I think you have it, you can use 87 octane and your car electronic ignition will adapt but you will notice a different car which is slower in speed.
you'll save a buck but will lose in other.

DRBC43AMG

Check this explanation: http://en.wikipedia.org/wiki/Octane_rating
as octane ratings are different (as usual....) from one country to another specially between the USA and Europe

Jovsky

Thanks guys for the info but going back to my question: Will it DAMAGE the engine using a lower 87 Octane rating rather than the recommended 91 Octane Rating? Or, our engines will just adapt to the lower octane rating just like kowalski was saying?

Actually I am not sold by my friend's suggestion to use lower rating since the manual states that you should fill her up with Premium Fuel which is 91 Octane rating. I believe that even if you are trying to save a buck using lower rating fuel but somehow I can sense that it will wear out the engine faster. Correct me if I am wrong.

Thanks for the info.

KJI3jflarryfe93

The 91 octane recommended in your owners manual is because this is the lowest octane your car can perform at it's best.
If you go to Mehico as an example maybe they have lower than 91, then you need to use the closest octane recommended.
newer cars with cats have electronic ignition, in Sweden 1987 cats were installed on many cars as an option.
buyer choosing a car with cats got a pinking sensor in his engine.
I used to have a Volvo 240 GLT 1988 long time ago.
My 1988 car didn't have a cat, NO pinking sensor.
If I had the 1988 cats version then I would have had the pinking sensor.
Difference in HP between both cars was 116hp for cat car vs 129 hp non cat car.
My car neede 98 octane leaded gas.

if you go to some countries with your car, they might offer lower octane than 91 which is recommended to your car.
if you fill her up with lower than 91 octane then your ignition will adapt to that lower octane to avoid pinking and damage to your valves.
your car will get slower and weaker with lower octane.
these newer cars uses harder alloys on those valves to resist damage.

non cat cars can't use unleaded lowoctane gas because valves will get damaged, you need to buy an extra octane booster additives and put it in the tank.
in Amedica you had unleaded gas for more than 30 years, am I right?
In Sweden this came late 80's IIRC?

Saaboteur

I don't think you'll damage the motor running with lower octane, but you won't get the best out of it, either in performance or fuel economy. The difference may not be noticeable on the butt dyno, but it should be there.

Jovsky

Thanks guys! you're all the best!

MarcusF

I believe using 87 octane can damage your engine. This is why I believe it can.

DRBC43AMG

MarcusF and his words of wisdom Great and thanks for the eye opener. I only use 98RON or better 100Ron in my C43. Works better and smoother

Jovsky

Once again, thanks MarcusF for the very informative article in the link. I knew my friend was wrong for being so cheap. Now, I'll have to show him MarcusF's article. Thanks again!

KJI3jflarryfe93

if you temporary use lower octane than the recommended 91 for your car, nothing will happen to your engine.
the ignition combustion will adapt to the lesser octane.
you will only notice that your car is slower and weaker, you will have to pull more on each gear to get the car go faster.

like I said before, if you go with your car to another country less fortunate than America that offers gas with different octane on the menu(lower or higher octane)
you need to pump the only offered gas available.
Best thing is to fill her up at home and when you need to fill her up again on vacation you can ad octane booster in your tank if there's no 91 octane offered.

your friends car would have broke down by now using lower octane!
it didn't, right?
he thinks he saves a few bux, but he needs to stomp harder on the throttle to get up in speed.
cheaper gas gives a slower car which needs a heavier right foot= car is thirstier.
save a buck or not with this driving habit?
maybe if he drives like a granny, yes!

Jovsky

No argument there buddy! It is true that putting a lower 87 octane rating in the engine won't break the engine right there and there and also you need to press the accelerator pedal harder to gain the desired speed.

KJI3jflarryfe93

no problems dude! :

thundercles

The previous owner of my c36, a good friend of mine, only used 87 octane fuel. He swore that premium didn't make a difference. Since getting it I quickly changed to 91 octane (AZ fuel pumps offer 87 89 91(premium) octane fuels) because I noticed after running out of gas when 87 octane fuel was used that it took a lot more failed attempts at getting the engine to turn over until the injectors were finally pumped enough gas to get it to start and once it did turn over it took a bit longer for that period of time when the engine acts erratically as the fuel system flushes the air out to end and the engine to act normal. My guess at the time was that the lower quality gas sludged things up a bit but it also could have just been the lower amount of energy it was drawing from the fuel that made it more tedious to get the car pumping fuel to the engine normally. It could also have just simply flushed more of the gas out when it ran out that time then the other times too.

But since then I have taken notice in the difference between how it normally runs with the 91 octane fuel I use and when 87 is put in instead which occasionally happened when I thought it might stretch my money further and pretty much always happens when someone else pumps the gas since they tend to hit the 87 by habit. I noticed a big drop in how many miles the car went for the volume of gas pumped with 87 octane, enough that I don't even try and kid myself thinking that I'll get more distance for my dollar with 87 octane, even when the station has 87 priced 30 cents lower then premium instead of the usual 20 cents. I personally vouch from experience for the statements about the retarded timing lowering the fuel economy stated in that page. Phoenix is almost exclusively urban sprawl (as one can tell by the very pitiful amount of tall buildings compared to similar sized cities) so even routine trips within the city can easily reach 40-60 miles one way a complete trek across the entire sprawl (gold canyon to sun city west) is 75 miles. Because of this gas mileage becomes pretty easily obvious. I pretty much see a drive to somewhere directly in the dollar amount it costs. In fact the drive back home from my friend's house in Peoria I just finished before hopping online now was an exactly five dollars trip . It's easy to see how my car racked up its 222k miles over its 15 year life here

austinholloman

Using lower than recommended can cause major issues in your exhaust system. Build up and eventual need for replacement. Like all others have said- It also hits you pretty hard in fuel economy too. MB didn't put a recommended rating for 91 oct. because its more pricey, they did it because the engineers that built these cars said too. Do as they say, the car almost always (( PLEASE don't listen to their claims of life time transmission oil! )) turns out better in the long run.

DRBC43AMG

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