Gas Prices - PeachParts Mercedes-Benz Forum

momentum · #1 02-12-2003, 01:20 AM

With today's gas prices, Is it safe to switch from premium grade to plus?

#2 02-12-2003, 07:23 AM

You do not indicate what model and year MB you are driving. With later models, there is a knock sensor that will retard timing upon sensing detonation. If you have the knock sensor, you will not hurt anything, but your mileage will decrease, offsetting some of your savings.

Indicate model and we can advise.

Good luck,

robi99 · #3 02-12-2003, 09:23 AM

My 300E calls for 91 Octane. If you are really concerned about saving money, you can fill up half and half with mid-range(89 Octance) and premium (93 octane) and you will be at exactly 91 octane. This isn't a real serious suggestion....you'll probably save $50.00 / year and is it really worth the hassle?? As Larry points out, your mileage will probably drop which reduces the savings. If you love your Benz, feed it the good stuff

Mercedes Fred · #4 02-12-2003, 10:09 AM

If gas prices hit $.80 a litre low grade, I may use it and use octane booster additives (which have not increased in price)
20 litres @ .60 = $12 (price 3 months ago)
20 litres @ .8= $16 (now)

the difference now covers booster at even at 20 L

when regular it gets that high, premium gas is in orbit.

Question: how "good" is that booster vs. pre-mixed?

momentum · #5 02-12-2003, 10:14 AM

sorry for the left out info. Mines a 87 300e.

Hurshi · #6 02-12-2003, 10:30 AM

My car is european version and has octane corrector. US version cars probably don't have it. With octane corrector you can set the ignition timing according to the grade of fuel you use. Mine has four positions. Below is a picture of the octane corrector located nearby the fusebox(under hood, on driver's side).
While using 87 grade fuel I tried switching between super and normal positions but never heard an engine knock when driving under load. So, I concluded that my car probably has a knock sensor that is doing a good job or else timing is already retarded way back by the timing management because of some faulty sensor.
If a person don't hear a nock while driving using low grade fuel under load does that mean that it is safe for the engine to use lower grade fuel?

Kestas · #7 02-12-2003, 12:03 PM

There was a lot of discussion on this last summer. Just search using the word "octane". The most comprehensive answer I remember was in a link provided by 95E320cab:

http://www.caranddriver.com/xp/Cara...keywords=octane

haasman · #8 02-12-2003, 03:28 PM

Shell gas station Monday, Feb. 10, 2003, in Pacifica, Calif.

(This is self-serve, BTW)

engatwork · #9 02-12-2003, 05:10 PM

My switch is going to be from the 300TD to the 240D for my daily driver

.

mithra · #10 02-13-2003, 07:39 AM

I generally average 60 to 80 k miles per year. Since the aquisition of the 600sel (apr 2002), I have tried various premium brands of fuel and tracked the fuel mileage the best I can. Generally speaking, my overall annual mileage is such that the car has to be fuelled every day. What does stand out (on this car), is the fuel mileage will always be best with the sunoco 94. I don't know why, but mileage is consistently higher with the sunoco 94. My driving entails 95% or better of highway, with the cruise typically set at 118kmh (72-73mph), or if on lower speed limit roads, typically 15kmh (10mph) over. What I have noticed is that the difference in fuel mileage between brands (in this car) can be as much as 20% for the same trip (approx same time of day, weather, minimal traffic). I do know from working with the fuel industry, that Sunoco 94 is the only fuel that has its own discrete dispensing system at the fuel terminal/storage yards, and that no other grade of gas or diesel is ever pumped thru that system (in Ontario anyway). I don't know if this is a factor for fuel mileage or not. So far, since owning the car my overall average fuel mileage is 24.7 mpg (imperial gal), with a high of 26.1 and a low of 18.5 (bad day in the city). I haven't tried a lower octane than 91, but from the posts I have read, it sounds like mileage will probably suffer enough to offset the potential short term saving (in this car). I haven't had the opportunity to track the mileage in the sl, but I am curious to see how it fares long term. The better half just has the sl filled and drives it, she doesn't put on enough miles to be concerned.

#11 02-13-2003, 08:02 AM

My office 178 miles round trip. The fuel prices are gonna kill me, but this is a small price to pay as compared to the hardships of civilians the world over during WWII.

May God be with our troops,

Crownwayne · #12 02-13-2003, 08:40 AM

Also be thankfull you don't live here in British Columbia, our Premier Gordon Campbell, (you may have already heard of him, since he was caught on a DWI in Hawaii at Christmas almost twice the legal limit) just announced a 3 cent a litre tax increase effective March 1st. I tell you this guy takes the cake, with oil prices already soaring and he decides to take a bite too. I hope he stalls the Provincial economy so we can send him back to Hawaii for good.

Mercedes Fred · #13 02-13-2003, 03:02 PM

Move to Ontario, Crownwayne!

In Ontario, they rebate your electricity bill ($75) and force the utility to sell electricity at lower than cost of production, reversing privatization and deregualtion that will end up costing tax payers far more than they would have spent as rate payers...but hey, they can just run it into a new gas tax to lower power costs...driving, like smoking and drinking, is a luxury, especially for your premier.

#14 02-14-2003, 07:14 AM

momentum,

I'm sorry I missed your response with year and model.

Your car has a knock sensor and will indeed prevent preignition if everything is working correctly which it most likely is. Running lower octane fuel will not hurt anything, but the savings will be small.

If you stay with premium, there is a resistor in a wiring harness near the master cylinder that you can remove that will increase the maximum ignition advance by 6 degrees. It will help take advantage of the premium fuel.

There was a thread about six months ago with many pictures of this resistor and its locations among different models. This resistor is in the circuit where the dial in one of the above posts is installed in Euro cars. The dial on the Euro cars simply changes the resistance in this circuit to compensate for fuel grade.

Good luck,