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Old 02-17-2001, 09:44 PM
ymsin's Avatar
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For the 300se W126, after a superb performance tuning, I switched to a higher octane unleaded (V-power @ Shell) from the Regular Unleaded - thinking there would be a big boost in power and performance.

I didnt think there was much improvement in the performance except where each refill was a little more costly. I was wondering if anyone has had any experiences from using a different fuel?
... Kerry

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Old 02-17-2001, 09:50 PM
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I use the regular unleaded in my Land Rover, it does not make a difference, now if you go on a long trip you can tell that you get better mileage. Looks like the same truck fills all the tanks at the gas station.
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Old 02-17-2001, 09:59 PM
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I am interested in the price you have to pay for fuel in Malaysia. Here in Colorado, USA, I purchase premium fuel for $1.559 per U.S. gallon or $0.412 per liter. A young man told me recently that his price in England averages 0.82 British pounds per liter, although I do not know if this is for premium or not. This is $1.188U.S. per liter, or almost 3 times the American price.
I have used medium grade fuel and premium in my 560SEL and have not noticed a difference, either. With the price difference so low here between regular and premium, it is not prohibitive to use premium. We also have octane booster products available in this country which I haven't used but would consider if prices were to rise.
If people in other countries replied with the fuel price they pay, I'm sure that we would all be interested. Of course, fuel is just one part of the economic equation, but it is common comparison item.
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Old 02-17-2001, 10:21 PM
ymsin's Avatar
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Price of Malaysian fuel is a controlled item - meaning it fluctuates only when the Government says so.

Super Unleaded (formerly leaded) is sold at RM1.10 (I think) [USD0.28) per litre.
Regular Unleaded is sold at RM1.20 (USD0.32) per litre.
Premium Unleaded is sold at RM1.35 (USD0.36) per litre - and only available at Shell kiosks. Vaporon technology, fuel that is used for F1 racing but modified for motorist.

USD 1.00 = RM3.80
... Kerry

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Old 02-17-2001, 11:29 PM
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Old 02-18-2001, 12:33 AM
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My '91 300SEL owners manuals indicates an octane rating of 91 is required. More than one post @ this site indicates 89 octane is sufficient. Some believe it's even better than the premium fuel.

I suspect that local altitude comes into play as well. The higher the altitude, the lower the requirement. Some say if it's not pinging, use it. Mine purrs on 93 octane; wouldn't consider anything else.
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Old 02-18-2001, 01:11 AM
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My 300E "requires" premium unleaded but I have been putting the cheap stuff in and havent noticed any knocks or pings at all. The regular unleaded around here is about 1.25 USD a gallon and premium is about 1.35 USD a gallon. Pretty reasonable but still too expensive. Anyhow I remember the day (summer of 1996 or maybe 1997) when regular unleaded was 67 cents a gallon, I wish it were still that cheap.
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Old 02-18-2001, 02:31 AM
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I've gone to 89 octane here in Chicago about $1.60. I have not notice any drop in performance. The car seems to like 89 better than 91 or 93 octane. I have been getting excellent performence when I jump on it. No knock whatsoever.
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Old 02-18-2001, 09:00 PM
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If your car doesn't ping or knock on 89, then its fine. 89 actually burns faster than 93 and should make slightly more hp. A higher octane will only provide more power if you bump up the compression or ignition timing.
'91 190
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Old 02-18-2001, 09:31 PM
Lim Lim is offline
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I am from Malaysia too. The fuel that ymsin mentioned, Shell V-Power, is asf:


Regular Unleaded at 92 RON
Super Unleaded at 97 RON
Shell V-Power at 97 RON

I always thought that cars only recognized the octane number, and can't really tell which brands they are. Any comment? However, when I used certain brand of fuel, my 260E will knock (in the hot afternoon at 35C) more frequently than the other brands. Anyone had those kind of experience?

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Old 02-19-2001, 12:34 AM
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Which certain brand of fuels you used had the knocking effect? I dont seem to notice any knocking-effect on the cars. The only observation I have is the carbon build-up when I took the spark-plugs out for a check. It was BLACK! I am hopinh V-power would knda clean it up , or otherwise to go for carbon-cleaning. Strange to see so much carbon build-up esp. since its hardly a year since the overhaul ...
... Kerry

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Old 02-19-2001, 11:05 AM
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This octane subject has been discussed at length at a VW message board I go to for my Passat. Yes a car that is rated for 91 can run on 89. The problem is that the engine's computer has to compensate for the lower octane and retard the timing, hense your performance and fuel economy will suffer. So you loose any savings you got from buying lower priced gas. My Passat has the 1.8, 20 valve, turbo engine. It requires at least 91 octane. Generally high reving engines require high octane gas. Hondas require only 87 or 89, but the Acuras require 91. Premium gas is a "cooler" gas in that it's design to burn at higher temps. vs. 87 oct. Running premium gas in car that calls for 87 oct. is generally a waste and may cause more deposits in the engine. Cars desinged to run on 87 oct ignite the spark plugs early, so premium gas does get burned completely. Now, like someone has already mentioned, running premium gas in a car that calls for reg. gas, on a long highway trip, will give some benefits. This would again be due to the fact that the engine is running hotter where premium gas works best, so you'll get better fuel economy.
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Old 02-19-2001, 03:33 PM
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You will not get any noticeable improvement in performance using any of your domestic market fuels if your car is tuned for your home market. In the UK we have 95 RON (premium), 97 RON (super) and 98 RON (superplus) unleaded fuels available at 0.75 GB pound, 0.80 GBP and 0.89 GBP per litre respectively. There is also 98 RON lead-replacement fuel available at about 0.80 GBP per litre to replace 4-star for pre-cat cars (btw, can catalysed cars use this fuel, now that it is lead replacement, rather than leaded?). FYI 1 GBP = about US$1.5 and these prices are per litre!! The guy from Illinois should count his lucky stars!

I use 97 RON unleaded in my C200. I get better consumption than on 95 RON fuel (about 1-2mpg better), but it's no faster. My father uses 97 RON in his Porsche 996 C4 because it says so in the handbook. My mum uses 95 RON in her SLK 230 (because she won't stump up a penny she doesn't have to) with no adverse effects. I'd piss in the tank of our Range Rover if I thought it would go, that thing uses so much fuel; 95 RON will have to do.

Merc engines are built to run on grades from about 85 RON. It makes little difference what you put in them so far as performance is concerned except at the very top end. And how often do you drive to the rev limiter?
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Old 03-02-2001, 12:01 AM
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I've started using 90 octane in my 87 560 SEL and it runs fine. Mid-grade gas around here (Minneapolis, MN USA) is usually 89 or 90 at different gas stations--I just find one with 90, I mean, why get 89 when it's the same price. During the summer, I'll probably switch back to premium 92 octane (some have 93 octane) so it's running at it's best when the weather is good.

Are there any other ill effects to running lower then recommended octane other then pinging or power/milage loss? I just don't want to damage or pre-maturely wear the engine out or something like that.


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Old 03-02-2001, 03:39 AM
ymsin's Avatar
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Its my thought that if you run a lower Octane gas, you'd promote carbon build-up as the combustion shall not be complete.

Unless I went off-track, I suppose I ought to be re-aligned.
... Kerry

126 tailed by a 203, 129 leading the pack.
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