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Mercedes 1986 300E 165,000 miles
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Discussion Starter · #1 ·
I have a 1986 300E 137K miles. According to the MB manual, I can use regular gas instead premium by retarding the timing. Has anyone tried this? If so, any pros and cons?
 

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300E 1987
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I burn nothing but premium in my 1987 but I have a friend with a 1989 who burns mid-grade and says it runs fine.

Regards,
Steve
 

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Depends on the day!
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check your timing, if it's around 3-6 degrees @ idle you can get away with regular.

Jonathan
 

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About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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If your car is set up to run regular grade fuel by retarding the timing a bit, the drawback would be reduced power. Just a fact of life (or physics): higher octane fuel allows greater spark advance which results in more power.
 

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If your car is set up to run regular grade fuel by retarding the timing a bit, the drawback would be reduced power. Just a fact of life (or physics): higher octane fuel allows greater spark advance which results in more power.

True, but these cars come to the US w/ such conservative timing curves.. The WIS even states that the level of tune/initial timing in US cars will results in decreased performance and economy...all in an effort to protect them from 'poor fuel quality' which to me has meant the mrs. dumping regular in a car w/ that would otherwise be set up w/ a very aggressive timing map!

Jonathan
 

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About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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Okay, Jonathan. Since I run at least 92 octane in all my 88s what can I do to get the most out of them? I think the 87 Service Manual says that the timing adjust resistor was moved to the EZL module but I sure don't see it. I thought I found the resistor against the bulkhead ahead of the brake master cylinder but now I'm not so sure. I pulled the resistor on the sedan but didn't notice any difference.
 

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-88 250D, -93 280TE-24 Sportline and -00 E270T CDI
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You should off course try a tank of each fuel and calculate whitch gives you the best fuel economy, with MPG vs. fuel cost..
My 300TE has got a timing selector knob in the engine bay , for "premium" and "super" fuel..
Off course i don't know what to select as my wife put "regular" in the tank and i put "super" in it :S
:)
 

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in my 93 300 3.2L, I tried tanks of 87 and 92 octan. I did not save the figures I got, but I do know that the cost difference in percentage between 87 & 92 was the same as the mpg difference in percentage using 87 & 92. In clearer terms the car got about 10% worse mpg using 87. Where I live, 87 is about 10% less $ than 92. So, it all evens out. A friend tried this on his Audi and got the same results. I run 92 at all times...
 

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86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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In an article I read by Patrick Bedard (Car & Driver) probably 20 years ago, he pointed out what happens to octane in gas when you "blend" two octane rating. For simplicity, say one rating was 87 and one was 92 and you put equal amounts of each rating in the tank. Rather than coming up with a rating that was (87 + 97 /2 = 89.5) the octane rating actually goes up higher than 92. I forget all the formulas that were used in the article, but I started practicing this during last summer when gas prices were nuts. I put 1/3 92 octane and 2/3 87 on a fill up in the 400E and kept very good mileage records. In my normal driving habits with the A/C on. I consistantly got 22.3 or a bit more in town driving and 28.7 on the highway. Running nothing but 92 octane, I get 20 - 21 in town and 26 - 27 on the road.

Since gas has dropped, I still practice this as the car just flat out runs better. Nothing scientific here, just my experience.

Good Luck to all,

Jayare
 

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93' W124 E36 AMG ; 71' Cadillac Eldorado ; 07' S211 280 CDI
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The eurospec fuel octanes are calculated in a different way, but anyway. Most of the time I fill up EuroSuper95, but sometimes I have it filled with SuperPlus98. I haven't seen a difference in fuel mileage nor in power (both Mercedes and Cadillac).
 

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Mercedes 1986 300E 165,000 miles
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Discussion Starter · #11 ·
Thats sounds good Jayare...I think I will try that the next time I fill up. The only problem is that I have to wait for the gas tank to be almost empty to maintain the right mixture.
 

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86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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not really. if you are at 1/4 tank, that means you needs about 12 gals. to fill up. Just start the test. On your original questions about changing the timing... Euro cars have an adjuster knob that allows you to change advance/retard settings depending on gas octane. No US cars came with this feature.

Good Luck,

Jayare
 

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99-C43, 05-G55K, 71-280SL, 94-E320 CAB
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Don't discount the difference in additives in premium versus regular.

Tier one premiums tend to have the additives such as PEA ( Techron ) which keep the fuel delivery system clean.

To me worth paying for the extras in premium as a preventative fuel delivery system maintenance method !
 

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I know chevron adds techron to all grades of gasoline, ie regular through premium.

Jonathan
 

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It was deemed illegal for gasoline retailers to claim different octanes of gasoline had different additives when, in reality, they don't.

I think one thing Mercedes latched on to was, way back when these cars were new, it was a different "class" of automobile which used 'premium'. Whatever. These engines are not high-compression or high-performance, so mine sees regular, as did the 4.2L in the 126 I used to have.

Sure, you can advance the timing to get a hair more performance, but I am never likely to use it enough to warrant the extra cost. My 124 sees full-throttle once a tank...maybe, and that's likely between 20 MPH and 45-60 MPH.
 

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190E 2.6 5spd
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You should off course try a tank of each fuel and calculate whitch gives you the best fuel economy, with MPG vs. fuel cost..
My 300TE has got a timing selector knob in the engine bay , for "premium" and "super" fuel..
Off course i don't know what to select as my wife put "regular" in the tank and i put "super" in it :S
:)
Timing knob? what? Which models have that? Only TE's?

I checked on my mech's Euro 300E but didn't see any knob.. where is it supposed to be?
 

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1993 400E
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I run my E420 "HARD". I use premium. .:thumbsup:


 

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1988 M-BENZ 300E | 1991 FORD PROBE GT TURBO | 2003 FORD EXPLORER 4x4
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Chevron/Texaco 93 only here.

How do you adjust the timing on these cars, I might like a little more advance for a little more passing power. Just need to figure out why the ass of the car wonders when I pass though. Must be a soft rubber bushing crushing under the tourq.
 

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you can only adjust timing from 0-2500 RPM via the R16 resistor.

Jonathan
 

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"Gretchen" my 1986 300E 286000 km+ (RIP) August 2015
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Well guys I gave the blended theory a try last Sunday. I was down to the reserve and I put 5 gals premium and 5 gals regular, this brought me up to a little over half tank. To date I have traveled 147 miles and still have a 1/4 tank left so something must be going on with mileage improvement. I will give another try and then make a final determination. As an added note I also tried a can of Restore, combined quicker starts, smoother acceleration and better mileage, another week and the final results will be posted. Good Luck.
 
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