Hi,

I recently bought a used 97 SL500, and I was wondering if anyone knew where the performance chip is located, and whether I can identify whether it is OEM or aftermarket. The reason is that I noticed that the muffler tip is not OEM, and I think the muffler system itself could be aftermarket (because it's louder than the usual). In which case, this owner might have invested in an aftermarket chip, and therefore I should NOT be putting in lower octane fuel.... :p

Thanks!

Your M119 engine should be running on premium unleaded even without a chip. You can run it at lower octane levels without significant damage (thanks to the knock sensor), but you'll be losing power.

Troy
1995 E420 86k

are you kidding me? it says premium unleaded only right under the fuel gauge. heres a tip... read your manual. there is a reason that car cost so much when it was brand new.

icetrey, why don't you read my post carefully? I asked for the location of the chip, not cynicism.

Thanks y2kimmel, I've been mixing 91 & 87 as some threads here have suggested. But I still need to know if I have an OEM or aftermarket chip, because the aftermarket would disable the knock sensor. At least with the OEM chip, I can run the 91/87 cocktail and know that if there is any preignition, the knock sensors would do its thing....

reading carefully you say... well, i was refering to your use of low octane gas... didnt have anything to do with your chip. anyways, what does it matter if you have a chip if you insist on putting cheap gas in your car? you buy a benz (which is a luxury car) and then you put cheap gas in it... kinda like ordering fillet mignon and covering it with ketchup.

When it comes to gas, expensive does NOT equal better! Now, the engine may require higher octane gas, but the concept of calling higher octane 'premium' is purely a marketing idea designed to trick people into thinking they are putting 'better' gas into their engine. Higher octane just means it burns at a higher temperature, not that it makes more power, or is cleaner, or better, or anything. My friend's race team runs 87 octane because thats the way they tune their engines, low compression and EGTs w/ high volume. Your argument that it is an expensive car and hence needs expensive gas makes no sense. Choose the octane that is best for the engine's design, whether that is cheap or expensive, that will be the best gas for the car.

That said, the engine may need the higher octane based on higher compression. I don't know exactly where the chip is on the engine, so I can't advise there. Can't you ask the PO? Or are they long gone? If you can't find out, you can always run 91, which is a good middle of the road octane.

Peace,
Sam

__________________
"That f***in' biodiesel is makin' me hungry."

1982 300TD Astral Silver w/ 250k (BIO BNZ)
2001 Aprilia SR50 Corsa Red w/ 5.5k (>100 MPG)

No, I can't ask the PO because I got mine from a used lot. Here in LA, though, 91 is the highest octane, and it get's premium pricing. I've been mixing 91/87, but I think I'll go back to straight 91 until I can find my chip and confirm that it's OEM.... :p

Hey Phil... If you read the manual on any Benz with a 3.0 or better engine 89 and above (89 is the last year I looked up) you will see that the compression ration is 9:1 and up... that is why you put premium (HIGHER OCTANE for those grammatically challenged) doesn’t have anything to do with price... I said cheap because there is a difference between having a low price and having cheap gas... there is a reason a SATURN is built to run 87 octane.
Just curious... is your friends’ race team built of Saturns? (OK I will give you props if you are using an old car with a low compression ration) but that will give you but only so much power (referring to the compression ration there, don’t go off on a tangent) why do you think that the fastest cars in the world (F1's) run? Pac West runs a Benz engine in their Champ Car... do you think it would even run on 87? Possibly, but I think there is a reason they use methanol. Do you think methanol doesn’t give you any more power? What about 103 octane... I can go get it down the street for about 4.25 per gallon... think that wont make a difference?

91 octane or above... there is a reason why this is in the manual.

With you being such a smart guy wouldn’t you think I would rather put 87 in my tank since it costs about 30 cents less per gallon than 93.

Octane rating and compression ratio are usually tied together, but not always. There are many factors that influence the octane requirment, including the squish area, shape of the combustion chamber and valve timing. It is possible to build a high compression engine that uses regular gas, and some Toyota and Honda models do just that.

Pretty much every MB imported into North America over the last 20 years has required 91 or better octane unleaded gasoline.

jsap, with your car, just keep 'er filled with the highest octane you can get, and she'll be fine. If you have to put some 87 or 89 in, don't fret, just don't fill it, and top off with 91+ when you can. Your SL has a knock sensor and will retard the timing if it does detonate, but I personally don't like relying on them.

Some good info on octane in case anyone is curious...

(the higher the octane, the more resistant the gasoline is to "burning.")

http://auto.howstuffworks.com/question90.htm

And Bruce Hamiltons excellent FAQ on gasoline...

http://www.turborick.com/gsxr1127/gasoline.html

__________________
John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

You're pretty quick to jump down someone's throat when you think they might be wrong, but you're certainly not willing to listen to anyone else. Sheesh, with less than a dozen posts you're already pissing off a half dozen people? Are you 12 years old?

__________________
John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

For the record.. my Saturn VUE recommends premium... also, the ION Redlines require premium....
I work for a Saturn retailer... they are not as low tech as some people might think... a Hyundai being built to run on 87 is a better comparison.

~D.J.~

The racers in question are actually motorcycles, Aprilias in the 1000cc to 50cc classes. Rotax v-twins and the like. But still fuel injected gas engines. Your dismissing of low octane fuel as something that 'cheap cars' use shows that you still don't fully understand the octane/engine design relationship.

Like mentioned, there is more to octane choice than just compression. Again, expensive /= good. If your car requires high octane, then it requires it, but just being an expensive or fast car doesn't mean it requires expensive gas.

I'd suggest, as an experiment, putting a tankful of that 103 into your car. I'm betting it will run very poorly. Because, as I said, expensive does not mean good, just different. The higher cost isn't because there is more power to be had, just because of supply and demand, less of it is needed, so less of it is made, so it costs more. Also, there are a lot of suckers out there who can be convinced to buy premium even if their vehicle doesn't need it, just by making it seem 'fancier'.

peace,
sam

__________________
"That f***in' biodiesel is makin' me hungry."

1982 300TD Astral Silver w/ 250k (BIO BNZ)
2001 Aprilia SR50 Corsa Red w/ 5.5k (>100 MPG)

All I was trying to say was READ YOUR MANUAL... it states, "Use premium unleaded only"... now what does that say to you? Use 87? NO... It even goes on to say that you should use 91 octane or above. I don’t particularly care about the price.... when your manual tells you to use something you don’t go buy the cheap (inexpensive) gas because you want to save 30 cents per gallon, especially when the manual tells you that if you must put lower octane gas in your car only put enough in to get you somewhere where there is 91 or higher octane and also that you shouldn’t run over 3000 RPM (could be 3500RPM) until you get the higher octane in the tank. At least that is what it says in my 89 300E manual.