Mercedes-Benz Forum banner

1 - 15 of 15 Posts

·
Registered
1988 190e 2.3
Joined
·
101 Posts
Discussion Starter #1
Hi, New to this forum and a new 1988 190E 2.3 owner!!! First Benz and I love it. A great find that was really well maintained with 280K!!!!

What is the deal with "use premium gas only" what are your viewpoints on the subject? Especially with such a high mileage car. Appreciate the help!
 

·
Moderator
2.3-16 | A3 2.0T | 986 Boxster
Joined
·
5,048 Posts
Welcome. Please finish your profile.

Try the search function on this forum for this subject. It has been discussed here many times and you are sure to find an answer to your question. These cars are designed to run on 91 or higher octane, regardless of how many miles you have on the odometer. You are in California?
 

·
Registered
1991 190e 2.6 automatic
Joined
·
760 Posts
i haven't found any difference in my 91 2.6 between 87,89,91,94


for the longet time i ran it on 91... then 2 months of 94 with resistor removed... thought i had better performance maybe 5% but gas milage was actually down 10%

now i am back to 87 with resistor in.. so far no difference


no pinging or anything... i don't mind that 87 is dirtier gas.. my engine is always seafoamed every 20K

also lookin at the compression specs, these engines actulaly don't have high compresson... a lot of honda's have higher compression and use lower quality gas
 

·
Moderator
2.3-16 | A3 2.0T | 986 Boxster
Joined
·
5,048 Posts
Lower grade fuel is not dirtier, isn't refined any different and doesn't contain anything magical to make your engine cleaner. Premium fuel is just fuel that contains a mixture of hydrocarbons that are slightly less combustible than those found in lower octane gas. So, higher compression engines using more combustable fuel (lower octane) may and will suffer from power loss, engine pinging, knocking etc. This is called preignition and is not desirable. The pressure of the piston itself will cause the air and gas mixture to ignite prematurely during the compression cycle, creating a smaller, less powerful explosion... so performance will not be optimum. When performance is consistently not optimum this can over time shorten the life of other components, spark plugs, sensors, etc. So when premium is required and not recommended it's for a reason. In a pinch, lower octane fuel is fine to use (as the owners manual says) but for day to day use, these cars were designed to use higher octane. Weather or not your seat of your pants meter tells you it's slower or faster with one or the other is a moot point. An engine that isn't running as efficient as possible isn't going to reward you with the best performance or fuel efficiency... and isn't this whole discussion about efficiency anyway?

Most of this came from "how stuff works" google it if you want to read the 5 page article.
 

·
Registered
1988 190e 2.3
Joined
·
101 Posts
Discussion Starter #6
Premium Gas or Not Premium Gas

Welcome. Please finish your profile.

Try the search function on this forum for this subject. It has been discussed here many times and you are sure to find an answer to your question. These cars are designed to run on 91 or higher octane, regardless of how many miles you have on the odometer. You are in California?
Yes, I am in California. What's the difference? Higher emission standards? Thanks
 

·
Registered
1988 190e 2.3
Joined
·
101 Posts
Discussion Starter #8
Interesting stuff, rjb190e. Thanks. In lieu of what you said, when my 190e was smogged (California) the NO numbers passed, but were high. Mechanic thought possible carbon build up? The car had been garaged for a little while prior to me purchasing. Something like 6 months. Car seems to have plenty of pep. No sluggish behavior at all, but just to be sure I filled her up with Chevron with techron premium fuel. We'll see what happens! Thanks for all your replies.
 

·
Registered
'87 190E 2.3 Manual, '81 500SEL 4whl SLS, '91 300SEL
Joined
·
1,757 Posts
These older MB engines don't have extremely high compression ratios (only 9:1), so the main reason they should run premium is due to the spark tables that are programmed from the factory. Chances are compression ignition is not going to occur with a low quality gasoline. If you look at the design of the cylinder head and piston walls on the 8 and 12 valves, there's nothing really "special" about them that warrants the use of premium fuel. We have a 2002 Chrysler minivan with the 3.8 that's port-injected that only uses regular gas, and the compression ratio is 9.8:1, with nothing special about the head and block design when compared to the MB engines. The only difference is likely the spark maps, and frankly, I think the quality of gasoline (re: anti-knock properties) has increased over the years, so I wouldn't worry terribly about running regular or mid-grade, unless you notice something. A knocking engine will run worse and get worse gas mileage, even if you can't hear it (you often can't hear micro-knocks).

My dad has run our '91 300SEL on regular more than a few times with no adverse effects. However, I still run premium in my 2.3 all the time, just because I don't want to risk anything.
 

·
Registered
1989 190E 2.6
Joined
·
26 Posts
I have a 1989 2.6 that knocks and stinks badly if I don't use premium gas. The primaries fuel injection system also requires premium gas to keep it running clean. So now I'm paying almost $5 a gallon to keep this car on the road. Ugh.
 

·
Registered
1993 190E 2.6
Joined
·
106 Posts
"This is called preignition and is not desirable."

I think you are confusing pre-ignition with detonation. Pre-ignition occurs when a hot particle in the cylinder lights off the fuel mixture prematurely. Detonation occurs when two flame fronts are formed and then collide. Low octane fuel causes detonation . . . not pre-ignition.
 

·
Moderator
2.3-16 | A3 2.0T | 986 Boxster
Joined
·
5,048 Posts

·
Registered
1984 190E 2.3 engine Automatic, 2002 C240 2.6 Automatic
Joined
·
240 Posts
I never really thought about the octane ratings in relation to my Benz. I've always run 87 octane in mine... until today.

I just came back from running almost all the gas out of the car. I filled it up with mid-grade...91 octane. We'll see if I notice any difference in performance. I'll probably keep running 91 anyway, now that I realize the octane difference... Thanks for bringing up the subject again!
 
1 - 15 of 15 Posts
Top