Fuel additive, do you use it?

[Joakim]

I have heard that the Porsche engine needs to run with the 99 octane(or was it this or less, can't remember) fuel that the 95(e10 octane and 98(e5 octane fuel does not include some thing that are good for the valves.? Is this right?

My 924 is basically family car, my parents bringed it from Sweden to Finland when they moved in the mid eighties..

My father said that the valves has been changed for in sometime in the 924's life, that it can handle the 98 octane fuel too without the additive..

Is the real name for the additive octane raiser?

[Joakim]

Originally Posted by Jrboulder

The real question is do you ever get knocking with whatever you're running?

You want to run the fuel with the lowest possible octane that you don't get knocking with. That will produce the most power and preserve your pocketbook.

As far as the valves he might be referring to Leaded fuel and lead additives. Idk. We haven't done that stuff on this side of the pond since before I was born. Your motor is ok to run without leaded fuel.

Yes. I remembered wrong. That he was talking about the lead additives

[racer]

Lets not confuse the OP is in FINLAND.

Octane ratings for EURO fuels are not the same as US Fuels.

We use the RON+MON / 2. I think in Euro, its just the RON rating.

[Dave Colangelo]

Here in the US you should be fine running 89 or 93 octane depending on what your local gas stations offer, some also have 91. You should not need to add lead to the gas in these cars or any modern car for that matter. Most specifically take unleaded gasoline these days. All of my p-cars have well over 100K on them with out lead additive and no issues yet.

Regards
Dave

[flash968]

racer is correct

98 there is 93 here

[9FF]

Book says 98 RON (93) for the Euro version and any lead-free for the US version. So US can use 89-93 presumably because the US 924 had a lower compression ratio than European cars.

[Gawernator]

The 924 requires higher octane than the 944? My owner's manual /gas cap sticker says 87 US rating... 86 8v

[Joakim]

Not octane, lead addictives.... or something bad for nature..

If I have understood it correctly

[Joakim]

What does the lead additive do in or to a motor?



Does the motor run smoother or less smoother, or do I get more performance or less, or what?

[Gawernator]

Lead in gasoline increases the octane, which can eliminate pinging and knocking etc high compression engines like say the 2.7 liter 944 or the 951. However, the negative is that lead is all bad for the environment and what not and perhaps more importantly, it destroys catalytic converters.

[petrolhead611]

A friend runs an 83 924 with the standrd Euro compresssion and uses a lead substitute additive. The main thing with these additives is not to mix chemistries- choose an additive an stick with it. I use Millers brand in my 11:1 compression Rover V8 which regularly gets revved to 6200 without pinking.

[Guest765]

I wasn't going to but I need to know the answer to this. Why in gods name is anyone using a lead additive in these cars in 2012????? Even the cheapest lowest grade pump gas, in the US, is more than enough octane for these cars with stock compression. There's a reason gas is unleaded these days you know, because its not needed anymore.

Even the "euro" compression should never be enough to need anything more than 91 octane, us rating. According to wikipedia, the required rated octane in RON for the high compression 924 engine is 95 RON which translates according to the below table to only 90-91 us rated octane, readily available at almost any pump in the USA.


"EuroSuper" or "EuroPremium" or "Regular unleaded" in Europe, "SP95" in France 95 85–86 90–91


Again, I truly do not understand why anyone is using lead additive (read: poison) in their gas in 2012. Maybe if we were talking about an old 1950s era ford, but a 924???



Edit;
Even 98 RON looks to translate to 93 AKI, or us rated octane, which is available at any and every BP gas station. Sorry but lead additive just doesn't make sense. Its funny you guys are letting this slide when everyone jumped down that poor guys neck for wanting to use r-12 to refill his a/c, but lead additive is a-okay. Lmao.


Edit again;

fuel that the 95(e10 octane and 98(e5 octane fuel does not include some thing that are good for the valves.? Is this right?

No this is not right. I believe you've confused the need for ZDDP in the oil with needing some un-necessary fuel additive.

Dave basically answered this above. I should learn to read the thread.

[flash968]

yeah - lead is no longer needed in today's engines, with harder valves and valve seats, and better ignition controls. lead was used as an anti-knock agent, and as a lubricant to help protect the valves and seats.

[racer]

Again.. OP appears to be in FINLAND. Likely has a "euro" spec motor I would be suprised if you could find any "lead" in such an enviromentally forward part of the word as scandinavia anyways.

I imagine that the car will run fine without any additives.

[curtisr]

The manual in my '87 924s says to use fuel with an octane rating of 87 in North America; however, my '88 manual says 89 octane rating is recommended. Not sure why this would be the case... Any ideas?

[racer]

Originally Posted by curtisr

The manual in my '87 924s says to use fuel with an octane rating of 87 in North America; however, my '88 manual says 89 octane rating is recommended. Not sure why this would be the case... Any ideas?

In 1988 Porsche standardized their 2.5L base motor. All ran the same (higher) compression ratio (hence the 158hp us rating vs the previous 147hp rating), necessitating higher octane fuel.