DWP

A columnist in today's WSJ seems to say that the only reason to not use regular unleaded gas (87 octane in California) is the reduction in mileage and performance in a car intended for 89 or 91 octane. The column says that modern engine management systems prevent "knocking" (pre-detonation) from lower-octane gas. The column suggests comparing mileage with higher-octane gas against mileage with lower-octane gas, and going with the gas that has the lower cost-per-mile. That doesn't take into account possible reduced power, of course.

Is anyone using less than 91-octane in a W211 and, if so, any problems noted? A couple of threads on this subject ran in '03 and the gist of the discussion was "I always use 91/93, because that's what M-B/my dealer/my gas station attendant told me to use", or, "What? You only go up to 91-octane at the pump in California, instead of 93/95/nitromethane?"

Brian_I.

The difference in price/tank between the lower octane and the higher is only about $2 at the station I fill up at (76). To me I don't think $2 every 10 days is even worth the hassle of trying to figure out how much difference in performance and mileage I would get between the different grades.

Not trying to beat a dead horse here but if you can spend upwards of $60k on a car, why would you cheap out at the pump just to save two bucks?

SAguirre

When I lived in Florida, the choices were 86, 89 and 93. I always used 93 octane in Florida since 90 was below the recommended 91.

Here in Colorado, the highest octane rating is 91, that is all I ever use. Whenever I can I will use higher, but my cars have always worked well with 91, but I think that they worked better with 93. On a side note, every car I have had up here at 5,000 feet +++++ has always gotten better MPG, but they all loose a lot of power. So of course, I always notice a huge improvement doe to having more O to burn when I am at sea level.

In Germany the lowest grade was 91, mid grade was 95 and super was 98. All MBs for the US seem to be detuned enough o work with German's lowest grade. My 190E 2.3 16 used at least 95 octane in Europe.

I would imagine that you can safely use 91 with no ill effects. I have no choice here in Colorado.

Steve A.

luxury1

It is made to work on 91 and so was my '02 bimmer. I used 87 in my bimmer for about 1.5 years (30,000 miles) and experience no problems. I have not dared to do this in the benz yet but probably will in the last year I own it.

Double Eagle

Most cars today have knock sensors and will run on lower ocatane fuels but not give you the full performance potential that you paid for. It's also possible that lower octane gas will tend to carbon up more over time and further reduce your performance a small amount since fuel distributors tend to put more additives in their higher octane gas.

In my opinion, it's NOT a good choice to put in lower octane than the 91 recommended by MB unless you are at high altitude where the octane available is reduced by 2-3 points per grads.

Hal H

The E500 engine is 10:1 compression ratio. I wouldn't put anything other than premium grade in.

If you refer to the owners manual, it emphasizes to use premium; only use the lower grade if you are about to run out, but to go back to premium.

BudC

As someone pointed out above, you generally get more additives with premium fuel. When I owned a BMW they told me to use Amoco Premium to avoid a problem they were having with carbon build up.

I can't see why anyone would buy a world class car and then try to save a few bucks on fuel. If you check a source like Intellichoice you will find that the cost of fuel is insignificant in the cost of car ownership. The overwhelming costs are depreciation and the cost of money. Consequently, the longer you can drive your car the less it will cost you for car ownership.

BTW, some of this 91 octane fuel is so loaded with crap that it's a wonder some cars even run. Whenever I've had the chance to use higher octane fuel on trips I always got noticably better performance and fuel mileage.

As they would say in New York...forgetaboutit!

ThemisN

I have also found amoco premium to be good. Trying to find out more on the Sunoco Ultra (94 octane). But if I HAD to go lower on octane, itwould be no less than 91.

MB4Fun

I live in California where only 91 is available. If I am on a trip to a neighboring state and can get 93, does it do more harm to put in for a couple of tanks versus sticking with the lower grade that the car will be run on for 99% of its life?

Thanks

BklynBenz

lol, ive been running my car on 100% pure grease with no problems

http://www.greasecar.com/

scorchie

We have to go over this urban legend pretty often here in the forums... the reason the octane numbers are higher in Europe is because they measure it differently. If you read your owner's manual it will give the formula used when calculating the minimum octane; I believe it gives a different number for when the European rating is used (they may have taken this out of the W211 manual to save money--haha--thus pushing the burden of cost onto us forum readers).

Incidentally, the value used in Europe is used in the formula used in the US (RON+MON/2).

It's similar to why the horsepower rating in Europe is different. Or why weights and speeds are different. Oh, I'm sorry, they don't measure weight in Europe, they measure MASS. And why the money is different. Etc.

-s-

scorchie

You need to look around a little better if you think you can only get 91 octane in California (or in Colorado for that matter). You may want to consider using the Internet as a tool to help you find better gas!

-s-

BudC

Try that 93 octane and I'll bet you'll notice better performance and better mileage. It sure won't hurt anything. It seems I always get stuck in a state that's got smog problems or corn farmers so I get stuck with 91 octane fuels.