Running 87 Octane when 93 Octane is specified - PeachParts Mercedes-Benz Forum

lkchris · #1 09-14-2008, 07:42 PM

There is no evidence the "computer compensates" and it in fact is NOT designed to do so. This is simply wishful thinking and borders on fantasy to believe so. (I'd like, BTW, to see the "timing retarded" on one of the new distributorless cars--which describes all 1999-2005.)

The typical 6-cyl Mercedes engine is around 180 cu in and develops the same horsepower as an American iron boat anchor engine of around 350 cu in. It takes high compression--and consequently premium fuel--to accomplish this. The V8s are in a similar state of tune.

Maybe it's SOP to ignore what American car manufacturers recommend, but you do so very much at your peril with German stuff.

mpolli · #2 09-14-2008, 07:57 PM

Quote:

Originally Posted by lkchris

There is no evidence the "computer compensates" and it doesn't. I'd like to see the "timing retarded" on one of the new distributorless cars.

????

What do you mean?

Hatterasguy · #3 09-14-2008, 08:03 PM

The computer will sense the knock and retard your spark, so you won't hurt anything. You will lose some power, and mileage.

But its false economy, and really if you are looking to buy a Mercedes and the extra $3 a tank matters...

lkchris · #4 09-14-2008, 08:06 PM

Quote:

Originally Posted by mpolli

????

What do you mean?

How do YOU think you can do it?

Hatterasguy · #5 09-14-2008, 08:05 PM

Quote:

Originally Posted by lkchris

There is no evidence the "computer compensates" and it in fact is NOT designed to do so. This is simply wishful thinking and borders on fantasy to believe so. (I'd like, BTW, to see the "timing retarded" on one of the new distributorless cars--which describes all 1999-2005.)

Thats what knock sensors are for.

lkchris · #6 09-14-2008, 08:09 PM

Quote:

Originally Posted by Hatterasguy

Thats what knock sensors are for.

No it's not. They are for minor problems perhaps caused by carbon in cylinder, not for gross changes. This is "legend" that has been built up over the years, mostly again by wishful thinkers. The Mercedes manual would approve regular fuels if your fantasy were correct.

https://www.mbwholesaleparts.com/StarTuned/pdfs/LiquidJune06Star.pdf

Hatterasguy · #7 09-14-2008, 08:16 PM

Um well thats how ignition systems work.

Thats why modern cars don't ping anymore...

RConrad · #8 09-14-2008, 11:24 PM

PW: This was an interesting question with a load of OPENIONS. Here is some facts, help yourself, OK. I have three vehicles, all say use 93. A Volvo S-90, a 96 S-320, a 97 SL-320. I've been runing REGULAR sense NEW. VOLVO 80K, S-320 103K, and SL 78K.I use Mobile 1, 10w30 all year round. Volvo=23mpg, S=26 @ 75mph, SL=24 @ 65mph. PW, these are facts, not my openion. Have fun, the older S's are god ole sherman tanks, and the 320's get great milage for such a large car. Mine is the long wheel base model, love it. Ron

deanyel · #9 09-15-2008, 01:19 AM

Quote:

Originally Posted by RConrad

PW: This was an interesting question with a load of OPENIONS. Here is some facts, help yourself, OK. I have three vehicles, all say use 93. A Volvo S-90, a 96 S-320, a 97 SL-320. I've been runing REGULAR sense NEW. VOLVO 80K, S-320 103K, and SL 78K.I use Mobile 1, 10w30 all year round. Volvo=23mpg, S=26 @ 75mph, SL=24 @ 65mph. PW, these are facts, not my openion. Have fun, the older S's are god ole sherman tanks, and the 320's get great milage for such a large car. Mine is the long wheel base model, love it. Ron

Thanks for those facts, but those are some pretty loose facts. The two MBs require 91 octane, not 93, and the Volvo claim seems suspect as well. Here's my personal experience - which I would characterize as anecdotal rather than factual - in a car that requires premium fuel the additional cost of premium fuel is justifiable in better mileage. I have always found this to be true. Try running a 6.3 on regular. You may be proud of your 24-26 highway numbers but those are not good numbers for a 104 motor on the highway. I get 29+ in an S320 on premium which easily justifies the approximately 5 percent premium price premium.

RBYCC · #10 09-15-2008, 09:03 AM

Quote:

Originally Posted by deanyel

Thanks for those facts, but those are some pretty loose facts. The two MBs require 91 octane, not 93, and the Volvo claim seems suspect as well. Here's my personal experience - which I would characterize as anecdotal rather than factual - in a car that requires premium fuel the additional cost of premium fuel is justifiable in better mileage. I have always found this to be true. Try running a 6.3 on regular. You may be proud of your 24-26 highway numbers but those are not good numbers for a 104 motor on the highway. I get 29+ in an S320 on premium which easily justifies the approximately 5 percent premium price premium.

Don't forget that a premium first tier gasoline has additives that will keep the fuel delivery system clean.........

pawoSD · #11 09-15-2008, 11:46 AM

Quote:

Originally Posted by Hatterasguy

Um well thats how ignition systems work.

Thats why modern cars don't ping anymore...

Oh really? Our minivan pings all the time when you first start it up! So does our neighbor's.....she has the same van!

Run premium in it if its a gas mercedes. Like has been said, if you need to save that extra $2-3 a tank then you can't afford one in the first place.

E150GT · #12 09-15-2008, 02:27 PM

I don't think our 80's Benzes have knock sensors. My sisters 04 mustang pings like theres no tomorrow if you get the RPM's up.

Oracle12345 · #13 09-15-2008, 02:35 PM

Just a bad idea. Dont be cheap and buy premium gas. The amount you will be paying in repairs will be alot more in repairs and premium gas will be cheap once you get the repair bill.

Hatterasguy · #14 09-15-2008, 10:23 PM

Quote:

Originally Posted by pawoSD

Oh really? Our minivan pings all the time when you first start it up! So does our neighbor's.....she has the same van!

Run premium in it if its a gas mercedes. Like has been said, if you need to save that extra $2-3 a tank then you can't afford one in the first place.

Thats strange, it sounds more like a timing issue. It takes heat and a good load to the the gas to go bang before it should. More so in a lower compression engine like that.