Probably overly worried here, but I just realized the imbecile @ the gas station filled my tank with regular instead of super, which I asked for. (We can't pump our own gas here in NJ - another story)

Is this going to be a problem? Thankfully, it was only a half-tank, so I guess its like a 89 or 90 octane blend in there now. 1/2 regular, 1/2 super.

Thanks

You'll be fine. Here in TX I regularly ran 87 octane in my M103 during the cooler months with no problems. Then I would go to 89 and 93 as it gradually warmed up and I perceived slight pinging under heavy load at lower RPMs. You just have to turn the stereo off from time to time if you want to actually hear it. In NJ you can probably get away with straight 87 octane through June...

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

I live in oregon and I have a 89 300se. I only run 87 octane. I dont believe in cars that only run super 91. I have seen a few articles in Car and Driver and Road and Track about gas. Basically what they say is that regular vs super isnt a big deal. Arco(cheap gas) vs Chevron(top tier) is.

I run 87 in my 300SE, and my CV.

__________________
Regards

Warren

Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

ENTER > = (HP RPN)

Not part of the in-crowd since 1952.

OK, thanks! No worries then.

The 103 engine does not have a knock sensor; so low octane gas can definitely be a problem - if it causes ping and detonation.
Susceptability to ping depends on the overall condition and tune of the 103 engine; and, as stated above, the ambient temp.

That being said, I always ran 93 octane in my '91 300SE. Once I tried 87, and sure enough, it pinged. But, later I discovered my EGR valve was bad.
after replacing the EGR, I have rfecently tried 87 octane, and no pinging whatsoever, yet. It's about 80 degrees here in Dallas, so, when it hits 101 degrees, I may find I need to run higher octane. Before, it never concerned me to pay 15 cents more per gallon to pamper a $56K car. Now, paying 50 cents more per gallon in my $4k car is more painful.

Anybody else have any comments on the M103 and octane requirements?

DG

I've heard a lot of things about it being bad to use 87 in the M103....they need Premium or it can damage the engine...especially with no knock sensor.

Engine: $5000

Gas: extra 15-20 cents a gallon.....the math is easy here.

Not to mention it will likely run/perform better on premium and get better mpg's.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

I always wondered what harmful effects lower octane gas would have on your engine, other than poorer performance.

__________________
" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles

Octane just measures a fuel's ability to resist predetonation. That said, fuel efficiency aside, the proper octane for the M103 engine (or any other engine for that matter) is the lowest octane you can run without experiencing pinging. If your particular engine doesn't ping using 87, then 87 is fine. If it pings for whatever reason, just use the next higher-octane fuel until the pinging stops. If 89 gets the pinging to stop, 89 is fine. But you may require 91 or 93. The "premium" fuel requirement in the owner's manual is put there as a general rule for owner's who don't know the difference.

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

I believe the octane requirement is related to the compression ratio of the engine. So, you're saying that the higher the octane is the more likely it is to predetonate?

__________________
" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles

Higher octane fuels are more resistant to preignition which causes detonation (I may have goofed because I don't think predetonation is an actual automotive term).

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

That's okay. I don't know any better . . . .

__________________
" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles

Is $3-5 a fill up REALLY breaking the bank for you?

If so, maybe you should rethink driving an MB

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

The difference between regular and premium is usually $0.20 / gallon.

If your tank is bone dry and you put in 20 gallons, that's a total of $2.00.

I've seen people go out of their way to the cheapest gas station in town, and then run into the mini mart and buy a large Diet Coke and a package of Ding Dongs.

Duh, there goes your profit margin.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

Paul's profit margins are larger than mine because of his math skills ($0.20 x 20 gal.= $4.00).

; - )