When I lived in CA the trick to getting a marginal older car through the emissions test was to put in Chevron's best with the engine real hot.
Woody

What is the cost of a gallon of Starbucks coffee?

If you think our U.S. Congress is rotten, wait till you read this!

Do you know that there are 91 DIFFERENT FORMULAS of gasoline on the market in the U.S.A?
There are different formulas depending on the the EPA regulations in a given area. A case in point is the MANDATED Alcohol content in the farm belt. This mandate is to support the farmers and to be politically correct to get the enviromental vote!
g/f

a word to the wise - mid grade gas is their biggest rip off. it is cheaper to do half and half regular and premium that to buy this 89 Octane concoction that they sell...

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joE
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"
http://banners.wunderground.com/bann...L/Key_West.gif

89 is the same price as 87 here in MN. I run 89 in my new 2.6 190 no problems yet!

Kyle

In an answer to your question, I had a 94 Jeep that ran a little lean from the factory, and when going up a hill under load, if I rolled the window down while driving in the left lane which was also right against the hershey barrier, I could hear slight pinging.

Try to find a route that has the above, and you might be able to duplicate the results.

With your window down and even over 1 lane, you wont be able to hear it.

If you can duplicate it, take it even further, and experiment with different throttle positions, load pressures on the pedal, and different gears. Keep an eye on the r.p.m., gauge if equipped, you will learn a lot more about your vehicle this way, and hopefully get closer to your engine at the same time.

Kind of like Zen like...

Question fo Woody: Do you wash your car with surgical grade distilled water???,
After all, you're driving a Mercedes, so you should only use the highest grade available, Right?
JackD

Wow. Some bad advice in here. Its all about compression ratio, not performance. You may not hear it, but the engine can still have detonation, aka "pinging". Run what your engine calls for and go to Starbucks a couple less times per month to make up the "expense" difference. On a Ford 4.6L VTech ANY pinging will quickly destroy the oil pump. It practically disintegrates! I am not sure if an MB engine has any issue like that though.

If one spends $150/month in fuel. Premium is less than $30 more a month. Not a bank breaking difference.

As for gas companies telling people to buy premium. Never happened. Again, octane requirement is related to engine compression ratio. Thats all. I am sure gas companies call it "premium" for a reason, because they sure make a huge premium on it. But I really recommend you use what you should for any vehicle.

Side note: Some people like to "treat" their car with an occasional tank of premium. Bad idea if it calls for low-octane. The higher octane needs more compression to start a flame front properly. So the car adjusts. Then when you switch back, it has to adjust again. The entire time economy is impacted adversely.

Another side note: Did you know E85 is 94-98 octane?

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Not a fan of Wiki, but this is a good read on knock/pinging/etc.

http://en.wikipedia.org/wiki/Engine_knocking

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

My opinions: we all have one - Ha.

The argument that if you drive a Mercedes you can afford an additional $300a year in preminum fuel does not hold water with me. An '87 300E is a $2000 car at best. I doubt anyone would consider running one of these very hard, and expecting it to live long, no matter what fuel it had.

Mercedes indeed goes a bit overboard in their maintenance and fuel recommendations. It's to their benefit; these cars are driven in horrendous conditions all over the world, and MB wants to push owners to the very best maintenance, to help them retain their reputation for reliability.

The resistor chip in US models retards the overall timing quite a bit, obviously don't mess with it if you are going to run less than preminum.

The '87 103 has no electronic knock sensor, and the timing advance is only adjustable by changing the timing resistor. And the US resistor is pretty retardant already.

The 103 has aluminum heads with 9/1 compression. That's pretty low.

You can definitely hear knock and ping in the 103. I heard it once in over 10 years of running 87 octane fuel. I wound it to 5000 rpm at full throttle on a 100-degree day, and picked up just a bit of ping as it went past 5000.
Otherwise, zero indication of any issues running 87 octane in hot Dallas summers with the AC runining wide open.
Continued ping and knock will show up quite obviously in most engines by checking the spark plugs. I can't knowledgably say this is true of the 103 because I check the plugs at least every 10k miles, and have seen no evidence of spark knock damage for the last 125k miles.
Maybe I have incipient knock and don't know it, but......

For me, running 87 octane has seemed to pay off. over 8000 gallons used, at an approximate 30 cents savings = $2400 saved. Enough to overhaul a 103 engine if it's getting damaged and falls apart at a mere quarter-million miles.

Just my 2 cents.

DG

we run mid grade in all of ours with no problems. Probably 250k in various cars over the years.

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1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride). Sold with 179k miles. Replaced with Hyundai Equus

1994 e320 Cabriolet 108k



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


[/SIGPIC]

Just use 87 with stock timing. 91 octane when the temp gets above 90f aka summer.

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CENSORED due to not family friendly words