Observation on 98 vs 91 octane for the DS23

cactus61

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Fellow Frogger
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Sure this has been posted prior, so sorry if this is ancient history.

Just returned from a very enjoyable 7 hr round road trip in my D to Donnelly River and back, as an experiment I started with a tank full of 98 and then filled up from empty with tank of standard 91 for the trip back over the exact same route, long hills and all. The run was done at the speed limit ~100-110 kph most of the way regardless of incline.

I know many are happy running 91 in the D, though the manual specs are for 98 in a late model DS, however I can emphatically report that the pinging was very noticeable on the trip home, whereas I only got some pinging while gunning on one long climb on the way down.

I'm not saying anyone's right or wrong using either, as price and usage is a factor, but there is no doubt in my mind anymore that my particular motor (again not all) runs much happier on 98 (which I have always been using to date).

Cheers
M
 
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I know we are not comparing apples here, but I noticed an odd thing with the Sigma the step-daughter used to drive.
It seemed to prefer 95, was nearly the same on 98, but was terrible with 91.
 
I run my D Spec on 95, though that is getting harder to find sometimes, and 98 if I am feeling really flush or want to fang it a bit.

I never hear/sense pinking on 95.
 
I've used 98 on everything all the time: ID, DS, GS, CX, etc etc. Had to fill the ID with 95 in Godknowswhere, NSW as I had no other option and Harriet was gagging all the way to the next petrol station! An extra few dollars by going 98 octane for the power factor and engine preservation seems to work well for me.
 
I only use 98 in the Deesse. I'm not an adventurous type.

One question though, can you still get 91 without ethanol in it? Given the rubber parts I'm about to replace in my line trimmer, I don't doubt what it could do to forty year old fuel lines.
 
I've used 98 on everything all the time: ID, DS, GS, CX, etc etc. Had to fill the ID with 95 in Godknowswhere, NSW as I had no other option and Harriet was gagging all the way to the next petrol station! An extra few dollars by going 98 octane for the power factor and engine preservation seems to work well for me.

Sounds about right .... the ID I find quite strange.... Those things have hardly any compression 7.5:1 .... it should near bloody run on kero without pinking :p I've always put anything that'll burn into the ID19 when I was driving it :)

I guess I'll see soon. Hopefully the ID here will be on the road within the next few months.

seeya,
Shane L.
 
Sure this has been posted prior, so sorry if this is ancient history.

Just returned from a very enjoyable 7 hr round road trip in my D to Donnelly River and back, as an experiment I started with a tank full of 98 and then filled up from empty with tank of standard 91 for the trip back over the exact same route, long hills and all. The run was done at the speed limit ~100-110 kph most of the way regardless of incline.


BEWARE ! Pinging at low speeds is obvious , But at high speeds & loads may not be heard. It can very quickly burn holes in pistons.
Ask how I know ! Clue : A set of Bristol pistons was VERY expensive
Cheers, Richard
 
I run all cars on 98. I would run the 2CVs on 198 if it were available, I need the power. If you had a 7 litre low compression V8, 91 may be OK.

John
 
I've got a 3 cylinder 505 SLi wagon here at the moment (engine comes out next week for rebuild) which was run on 91 and the driver didn't back off when it pinged.

XU 10 from a 405 with unshaved head and the thickest head gasket runs perfectly on 91 in a 306 XT (the 1.8 blew up twice before re-engining)

The different experience with the IDs (Shane and Donat) might be solved by measuring the depths of the cylinder heads- one might have been machined.

Bruce.

PS if it makes pinging noises, back off enough for them to stop. Failure in cases of prolonged marginal detonation is either ring lands (which is what has happened to the 505 SLi) bearings failing (low oil pressure, knocking from a cold start) or crankshaft cracking.

If you really want to see the effects of detonation, have a look at the ATSB website.

I have just fitted a 0.8 mm shim to an unplaned 504 square port. It was ruuning E10, but need the timing retarded to do so, so ran hot and not very efficiently.
 
http://atsb.gov.au/publications/investigation_reports/2000/aair/aair200002157a.aspx

If this is what I hope it is it shows some info on detonation. Relevant info starts on page 113. There is a supplementary report on the failure of the second engine which is more informative, including crankshaft cracking due to detonation. I'll see if I can find it.

http://atsb.gov.au/media/1292159/aair200002157_001.pdf See pages 39 to 40 and 59 (page numbers in report)

A broken crank in a car isn't too much of a safety issue, but it is depressing to try to rebuild a rare old car only to find that the crank is cracked so isn't worth re-grinding.

Bruce.
 
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Sobering stuff, nothing less than 95 in the old girl again for me, it was a one off but reading this wish I hadn't tried it even once. Will have a word to the friend who suggested that running them on 91 was fine.
 
If you missed my unusually subtle hint earlier (thanks SLC206 for that handy phrase), the correct terminology is PINKING. As in PINK with ING on the end.

Pinging is what happens when cops catch you speeding.
 
If you missed my unusually subtle hint earlier (thanks SLC206 for that handy phrase), the correct terminology is PINKING. As in PINK with ING on the end.

Pinging is what happens when cops catch you speeding.

Saw that and chose to ignore :clown:

...but since you have brought it up.
http://en.wikipedia.org/wiki/Engine_knocking
http://www.cartechnical.co.uk/p/128-pinking-pinging.html

Whether correct or not both are now acceptable terms for engine knocking/pre-ignition. Pinging is probably the more common useage in the UK from my distant recollections.

98 always in all our petrol cars, the few cents saved at the bowser is likely recovered in distance travelled. Any info on that sweeping statement Cactus61? Certainly a saving if your car is prone to 'ping/pink' on lower octane fuels i.e. engine rebuild.

Cheers
Chris
 
I retarded the centrifugal advance curve a small amount by increasing the tension on the springs. ( You bend the little spring post outwards on the Ducellier distributors). After that I was happily able to put 91 RON into the machine without any sign of Pinking.
 
98 always in all our petrol cars, the few cents saved at the bowser is likely recovered in distance travelled. Any info on that sweeping statement Cactus61? Certainly a saving if your car is prone to 'ping/pink' on lower octane fuels i.e. engine rebuild.

Cheers
Chris

To be frank, the $/milage has never been a concern as I simply don't think that way about old cars, if I want milage or save $ etc I hop into a different wagon. I always used 98 simply because that what the original specs said was preferred. The reason I tried 91 was that when I asked a very experienced local citroen person what he used in Ds when I first bought it, he said 91...I chose to ignore this for a couple of years until this week. I'm glad I did :)
 
To be frank, the $/milage has never been a concern as I simply don't think that way about old cars, if I want milage or save $ etc I hop into a different wagon. I always used 98 simply because that what the original specs said was preferred. The reason I tried 91 was that when I asked a very experienced local citroen person what he used in Ds when I first bought it, he said 91...I chose to ignore this for a couple of years until this week. I'm glad I did :)

Definitely agree with that, I'm more inclined to put $40.00 in and run the car until it needs another $40.00
With regard to fuel, what we get now as 91 is probably nothing like the good old days of leaded fuel, but even back then I always ran mine on the higher octanes available, the car just responded so much better and you certainly knew if you had a bad batch.

Cheers
Chris
 
I probably wasn't clear with what I posted before... the Mitsubishi actually seems to run better on 95 than what it does on 98.
Any ideas why?
 
The problem with 91 is the carbon deposits it leaves in your inlet tract/around valves/injector nozzles etc. Engines which run exclusively on 98 have clean inlet ports.
 
If you missed my unusually subtle hint earlier (thanks SLC206 for that handy phrase), the correct terminology is PINKING. As in PINK with ING on .


It's french I think you'll find... the "k" is soilent..

Matthew :)
 
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