Is unleaded OK

[Stiffy]

Pinging is the only additional problem I've had - my local mechanic suggested an octane additive, but at between 15-20 bucks per 50 litres, on top of the cost of premium unleaded (98) - $1.30 per litre, I'm expecting a complimentary knighthood from Saudi Arabia any day now.

I think retarding the spark might be a better option - and should also be borne in mind when being concerned about burning out valves.

There are differences in the quality of petrol in Australia as well.

Today Shell released 100 octane petrol with 5% ethanol - does anyone have a take on this?
Also, when I did put an octane additive in my tank, the exhaust fumes smelt peculiarly of burnt kerosene - what's that all about?

[OzBenzHead]

Today Shell released 100 octane petrol with 5% ethanol - does anyone have a take on this?

From my former extremely infelicitous experience with ethanol-blended petrol, it will only get into my Benzes' tanks over my dead body!

Also, when I did put an octane additive in my tank, the exhaust fumes smelt peculiarly of burnt kerosene - what's that all about?

Some additives are little more than flavoured kero - that's probably why.

I have always used ValveMaster but, as of receiving the recent advice from Stuttgart, I'm abandoning that apparent waste of money. I'll just stick with my usual 98-RON juice from Caltex, Ampol, BP, or - at a pinch - Shell (they've had refinery problems a couple of times with their PULP which have resulted in a nasty brew).

[Stiffy]

I just did a bit of a look on the ethanol question and you're very right: pre-ignition among other nasties
http://www.fcai.com.au/ethanol.php/2005/11/00000005.html

Vehicles with carburettor fuel systems may experience hot fuel handling concerns. This is because the vapour pressure of fuel with ethanol will be greater (if the base fuel is not chemically adjusted) and probability of vapour lock or hot restartability problems will be increased.

For the 350SE
In addition to the issues mentioned above for carburettor equipped engines, the use of ethanol blended petrol in fuel injection systems will result in early deterioration of components such as injector seals, delivery pipes, and fuel pump and regulator.

So, maybe I'll start an eBay business selling kero to the octane challenged - there's large amounts of cash to be made.

[Mforcer]

Hi Stiffy and welcome to the forum.

You should not be experiencing pinging on premium unleaded. If your mechanic is suggesting adding an octane booster, perhaps it is time to find a different mechanic. Even MB specialists can use a second opinion at times.

As for Ethonol in fuel, it is something I would not be willing to try for long periods. It supposedly can clean out your fuel system to the point of taking the rubber hoses with it. Newer cars use different materials in their fuel systems and may not have the same problems.

Also just remember that a higher octane fuel does not make a better fuel. For our cars, 98 is recommended. Anything under this may cause early detonation of the fuel (pinging) while higher octanes will not make any difference. On modern, high performance and especially turbo cars, the higher octane fuels can be managed by the on-board computer systems to gain maximum performance. This performance gain is achieved by setting the fuel detonation point as late as possible as allowed by the fuel. Without the on-board computer, the detonation point is fixed and so no further performance increase can be achieved.

Cheers,
Michael

[Stiffy]

Thanks Michael,

Hopefully the 50 litres I put in earlier today won't dissolve my car - and I do need to get myself a new mechanic.

[John Hubertz]

Styria....

For those of us with short attention spans and the inability to concentrate long enough due to a lifetime's habit of learning from people like you, would you please clarify one thing....

Are you saying that the hydraulic lifter/cam follower assemblies on 4.5 liter cars have an adjustment?  Wow!

(laughs)

(of course, I once "accidently" signed off on serviceability requirements for the new Aerostar van, that required engine removal to service the valve adjusters....)  (ooooops)

(my performance review that year included the term "benign neglect")

(so did my divorce papers a couple of years later......  hmmmm)

John