Choice of best fuel

[John Ciab]

What is the best choice of gas for my 1970 280sl? Is it best to use ethanol free 91 octane. Or 93 with 10% ethanol . Is there an additive that I should consider?
Thanks

[georgem]

John,
For older cars, the consensus seems to be to stay away from ethanol in any concentration - too much old style rubber in the fuel system which can't cope with the ethanol.
And just to highjack your thread slightly, over here we have 91, 95 and 98. I use 98 because she seems to like  it - is it my imagination or am I wasting my money?

[Steven A]

John,

Apologies for late response.

As commented by George, concur keep away from ethanol - we did assessment for the Gov't in the early 2000's on effect of ethanol level when it was being considered for implementation here in Australia both for automotive and non-automotive engine applications.    The assessment particularly looked at the effect of ethanol on older cars - given that based on the registration statistics, the average age of cars in Australia is around 10 years - and the effect on the rubber, and some other material, components was the key issue.   If I recall, beyond about 15%, driveability was starting to be affected as well as emissions etc.   If interested, contact me on my email address and  I could dig up the reports  (the reports were also published by NMMA in USA).

I use 98 (this is (RON+MON)/2, same as AKI in US, plus an additive - the original valve seats etc were all set up for leaded gasoline, and 98 offers the best protection with the unleaded fuel.

Regards

[Cees Klumper]

Actually the valve seats are 100% ok for unleaded fuel, no need to go to 98 octane. I always use 95; my motorcycle even gets better, not worde, mileage with the 95 over the 98.

[jameshoward]

I've been looking into the ethanol thing this week, as I was in North Carolina where it's possible to purchase fuel without ethanol. Alas in New Jersey, it is not possible to purchase fuel without ethanol, or so it seems. So I'm stuck with the stuff. If there's anything I can add to the fuel to help prevent damage to the hoses I'd like to hear about it.

[philmas]

Here in France, the choice is limited to 95 E10 ("eurosuper") containing up to 10p cent ethanol, and "super 98", up to 5 pcent ethanol...which means ethanol in any case.I went for Super 98 from the beginning, and still have nothing to complain about for more than 15 years.

[JonathanB]

I found this site that shows where one can obtain ethanol-free gas in the USA:

http://www.pure-gas.org/index.jsp

[450sl]

For What its worth:

A friend did a private fuel test , he took  clearglass bottles and bought fuel from 4 different brands available overhere.
he put a o-ring  and a piece of alu and steel in each bottle and let it rest for 3 years.


over 3 years they all lost weight :

BP Ultimate 98:  (-102 g)
Tango Euro 95:  (-147g)
Aral 95E10:      (-184 g)
Haan BlueOne 95 : (-154 g) 


In the the first two bottles  o-ring and metal parts where like perfect  and   fuel was smelling like fresh fuel.
In the the last two bottles  o-ring  very brittle and corrosion on metal parts.  fuel was smelling like dead fuel.

[Bonnyboy]

I was down in the USA (Washington State) on the weekend and was talking to the guy at the gas station about ethanol free fuel.  They had some and I was very excited.   The guy suggested that most farming communities will have a gas station that has ethanol free fuel for the farm implements.  He suggested getting of the highway and finding the gas stations on the secondary roads and if there is a card lock they will probably have a pump for the public as well during normal hours.   

He said that he worked in a gas station on the main highway and they couldn't sell the ethanol free gas as everyone was after the cheapest gas for their cars, but where he is now (1 block off the highway next to a John Deere dealer)  they sell lots of ethanol free.