NickE63

Ok so I had no choice but to fill up with 87! Ever since my car runs like **** misfiring on most of its cylinders hesitation and check engine light on, I cleared the code and it eventually just comes back on, I now found a gas station that had super, so i topped off half 87 and half 93 now the car sometimes runs good and sometimes doesn't, what should I do?

Vic55

Must be your tune causing that----- cause a stock engine wouldnt misfire on 87 although you would see mal-performance no doubt.

Run the tank asap---- drive all over the place and refil----

NickE63

Vic I'm an hour and half away from my house doing just that, everytime it acts up I o pull over then shut it down and start it back up and keep going, thanks

2 '02 S600

That has been a concern of mine since this gas crunch. No 93 only 87 available, but I haven't had to fill up yet & I don't have a tune on my car. Hope this crisis is done by later this week. Good luck getting that 87 burnt off quickly & hope you're back to normal with a full tank of 93 octane.

FlatlineEF9

In the owners manual it mentions something about this. My 211 E55 mentioned not going above 3krpm or something of the sort. RKD (remolexi) was running 87 octane for a while and didnt have any problems...that i know of.

Incon306

Regardless of what tune you are running you should be able to run 87 octane all day long as long as you do not get into boost and you just drive the car like a "grandma". Does it act up at all if you're just cruising on the highway, at say 70mph, with cruise control on?

NickE63

yes it starts bucking hesitating and not even driveable unless i pull over turn it off and start it up again then it will eventually act up again, im starting to think its not the gas, i think its a fuel injector control module, going to dealer tom ill post the results

Incon306

Wow! It definitely sounds like something other than the gas if it's doing that while just cruising along at a steady RPM/speed. Definitely bring her in. Good luck!

Midcont

I filled up with 89 and with a tune I am having no issues.
I was going to get octane booster at the auto parts store but it hasn't been an issue.
I'll fill up next time with 93. By that time I would assume it will be available everywhere.

Incon306

I HIGHLY recommend that you do not go WOT with 89 octane in your tank especially with a tune installed. Drive around easy(mild acceleration) until your tank is almost empty and then fill up with 91 octane+.

Also, do not use or trust octane boosters as almost all of them do not work well. When they say it will raise your octane by 5 points that means your 89 octane will become 89.5 octane. Each "point" is really 1/10th of an octane number.

kip

I dont get the problem. Why not drive a few miles and fill up as much of high octane fuel (like 99 octane) as one can buy, it mixes ending in higher octane fuel, right?

NickE63

just picked up the car, mercedes changed the plugs and car is stronger than ever, why it got fouled out is not known? but im back in business

BSpencer

I don't drive an E63 nor do I live in the states but I just came across this thread and i'm amazed you can actually buy such fuel? What is the norm for US petrol ( or gas as you call it ), ~91 octane?

Surely in something like an E63 you'd be getting nowhere near the 525bhp figure on paper using that stuff? I once saw a test on a motoring show which proved that in tuned cars fuel plays a huge part in providing the full bhp the engine is capable of.

Here in the UK the minimum you can buy is 95 octane and the super unleaded is either 98 or 99.

kip

Quote:Measurement methods
The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel through a specific test engine with a variable compression ratio under controlled conditions, and comparing these results with those for mixtures of isooctane and n-heptane.

There is another type of octane rating, called Motor Octane Number (MON) or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally fuel specifications require both a minimum RON and a minimum MON.

In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90-91 US (R+M)/2, and even deliver 98 (RON) or 100 (RON).

The octane rating may also be a "trade name", with the actual figure being higher than the nominal rating.[citation needed]

It is possible for a fuel to have a RON greater than 100, because isooctane is not the most knock-resistant substance available. Racing fuels, straight ethanol, AvGas and liquified petroleum gas (LPG) typically have octane ratings of 110 or significantly higher - ethanol's RON is 107 (MON 89, AKI 98) reference[2]. Typical "octane booster" additives include tetra-ethyl lead and toluene. Tetra-ethyl lead is easily decomposed to its component radicals, which react with the radicals from the fuel and oxygen that would start the combustion, thereby delaying ignition. This is why leaded gasoline has a higher octane rating than unleaded.