LeeM Posted 17August, 2015 Report Share Posted 17August, 2015 I had an interesting (enlightening) chat with Mark Poole the other day regarding 98 ULP.I put 10 litres in the tank one day prior to dropping the car off, and he asked if it had any old fuel in it that I had not removed. He tells me that 98 ULP goes off after a certain period of time, and can cause pinging when the car is driven again after sitting idle for a month or 2 Some of his clients that race 911's have left fuel in the tank for few weeks in between race meetings, then had some pretty major engine problems at the next race. Basically, he advises to only put in what you really need for a particular trip, and not fill it up. Can anyone shed a bit more light on this? Do you fill your cars and leave it sitting? Just thought I'd bring it to your attention if you weren't aware Link to comment Share on other sites More sharing options...
Russ Posted 17August, 2015 Report Share Posted 17August, 2015 I think 98 from most places has a shelf life of about 6 weeks, I just make sure I change my fuel more often than thati think the lower grades are worse too Link to comment Share on other sites More sharing options...
Dreamr Posted 17August, 2015 Report Share Posted 17August, 2015 I generally only have my tank at a maxium of half full .... and that's if I'm going on a run .... by the time I get home my gauge sits on 1/4 or less.I'm not sure about the fuel going off, but from what I have heard, I certainly wouldn't leave a lot of fuel in the tank for exactly the reasons you have stated above.BTW ... I also only use 98 ULP and I've never had any issues at all. Link to comment Share on other sites More sharing options...
tazzieman Posted 17August, 2015 Report Share Posted 17August, 2015 Never had a problem.I use Stabil in my boat and any cars that are off the road more than a couple of months. Which is none , as I rotate the strike.Older high comp race engines are somewhat different to our street machines. Link to comment Share on other sites More sharing options...
Harvs11 Posted 17August, 2015 Report Share Posted 17August, 2015 I fill with 98 whenever the gauge gets near 1/4. Gets driven anything from 3 times a week to once a month. Never had any fuel problems. Link to comment Share on other sites More sharing options...
SteveT Posted 17August, 2015 Report Share Posted 17August, 2015 Ditto to Harvs above, fill up the tank when it gets down around 1/4 then a couple of months later repeat. Only use 98, never had an issue related to fuel. Both cars, old one and new one. Link to comment Share on other sites More sharing options...
LeeM Posted 17August, 2015 Author Report Share Posted 17August, 2015 Cool, thanks for the replies. Being a numpty, I always like to get a couple of extra opinions on these sorts of things Link to comment Share on other sites More sharing options...
StevepGT3 Posted 17August, 2015 Report Share Posted 17August, 2015 don`t get cocky and leave for months though,I have had to totally disassemble,ultrasonically clean injectors and rebuild 2 fuel injection systems,including replacing fuel pumps on bikes that were left unused for months. Link to comment Share on other sites More sharing options...
StevepGT3 Posted 17August, 2015 Report Share Posted 17August, 2015 Just to clarify, I am not talking about the fuel being a couple of months old as I have no evidence to suggest you will notice the difference,I am talking about not starting or driving for months, as once the fuel dries out in the injection rails or carby bowls it can(I have seen it) turn to a jelly like substance and has to be physically cleaned out. Also submersed fuel pumps if not fully submersed can and do sieze up.PITA Link to comment Share on other sites More sharing options...
Peter M Posted 17August, 2015 Report Share Posted 17August, 2015 I've always had a notion that steel fuel tanks should be keep full to minimise corrosion from condensation in the airspace. Is that idea similar to the one about not using the handbrake to avoid stretching the cable.... Link to comment Share on other sites More sharing options...
StevepGT3 Posted 18August, 2015 Report Share Posted 18August, 2015 I've always had a notion that steel fuel tanks should be keep full to minimise corrosion from condensation in the airspace. Is that idea similar to the one about not using the handbrake to avoid stretching the cable....Totally agree, and since getting caught out with rusty alfa tank and siezed fuel pumps, I fill my tanks on the way home, not on my way out possibly a month or so later. Link to comment Share on other sites More sharing options...
firstone Posted 18August, 2015 Report Share Posted 18August, 2015 I refill after every outing to avoid condensation. No fuel problem here.The info I have read, from fuel company sources says fuel lasts longer kept cooler. Link to comment Share on other sites More sharing options...
tazzieman Posted 18August, 2015 Report Share Posted 18August, 2015 Ah , the superior engineering of the mighty Porsche 928 Link to comment Share on other sites More sharing options...
LeeM Posted 18August, 2015 Author Report Share Posted 18August, 2015 I asked Mark about filling the tank before storing it for any length of time. His reply was that racers used to do that (including himself) yet for whatevere reason, they empty the tanks after a race meeting. I wouldve thought condensation would be a factor doing that (I did say that to him) yet I'm assured this is the practise now Link to comment Share on other sites More sharing options...
hugh Posted 18August, 2015 Report Share Posted 18August, 2015 I haven't driven my red one in quite some time (at least 6-8 weeks), it probably has about 1/4 of a tank of fuel in it. Should I then be emptying this and refilling prior to heading out next time? I tend to only use BP (98) and the car is stored in a cool & dry environment.You have me worried now................. Link to comment Share on other sites More sharing options...
tomo Posted 18August, 2015 Report Share Posted 18August, 2015 If any thing like old motorbikes, we used to leave the tank full to stop the tank from rusting. Link to comment Share on other sites More sharing options...
Peter M Posted 18August, 2015 Report Share Posted 18August, 2015 Is this a storm in a teacup?I can neither tell the difference between using 95 or 98 nor the differences in brands when I drive.My tanks are sometimes full ("You beauty!") but often stored closer to around quarter full.My cars always start instantly as they are kept on charge between drives.The 30 year old steel tank and gauze filter looked fine and clean when I inspected it internally recently and I'm confident it will make at least another 20.The 20 year old plastic tank and gauze filter looked fine and clean when I inspected it internally recently too.I've heard of plenty of fuel myths and legends but afraid I haven't any data to contribute and will just continue with my ignorant ways. Link to comment Share on other sites More sharing options...
andrew911 Posted 18August, 2015 Report Share Posted 18August, 2015 I use BP 98 in all of my p-cars and never had a problem ... each one get driven at least once a month. I use injector cleaner once a year, but it does not appear to have any effect on how the car runs Link to comment Share on other sites More sharing options...
Peter M Posted 18August, 2015 Report Share Posted 18August, 2015 Andrew,Great suggestion for a new thread on "injector cleaner" once we master fuel chemistry! Link to comment Share on other sites More sharing options...
ByronBayChris Posted 18August, 2015 Report Share Posted 18August, 2015 Andrew,Great suggestion for a new thread on "injector cleaner" once we master fuel chemistry!geez..I'm still getting my tiny head around the oil thread. Now a petrol level thread, and soon an injector cleaning thread. What's next? Link to comment Share on other sites More sharing options...
firstone Posted 18August, 2015 Report Share Posted 18August, 2015 Coolant thread? ? ? Link to comment Share on other sites More sharing options...
StevepGT3 Posted 18August, 2015 Report Share Posted 18August, 2015 isn`t this what the internet is for, to make you worry about things that you had no idea that you needed to worry about.I think we should call it autochonriasis Link to comment Share on other sites More sharing options...
Peter M Posted 18August, 2015 Report Share Posted 18August, 2015 What's next?Who wants to do a group buy of German air for our tyres?I hear that the depleted ozone in Australia air causes premature hardening of the rubber compounds and therefore could be dangerous. I also read on the internet that our air doesn't have the same shock absorbing properties and those with adjustable Belstein's and Koni's need to run half a notch more rebound front and rear. Link to comment Share on other sites More sharing options...
LeeM Posted 18August, 2015 Author Report Share Posted 18August, 2015 Just relaying what I was told by a Porsche mechanic that builds and tunes race cars for a living. Whether its correct or not for a road car that isn't seeing mega revs is up to the chemistry boffins to chime in with their knowledge. It made sense to me, yet you have people saying one thing and others saying another, so believe what you want to believe until you find out the facts. I would think that a quarter of a tank at rest would be fine, then add new fuel to mix it up ready for the next hoon....errr....leisurely drive. I just wouldnt leave it for 2 or 3 months going by the advice I received Link to comment Share on other sites More sharing options...
cyberpunky Posted 18August, 2015 Report Share Posted 18August, 2015 Back when I use to display my old car, they had a rule at Jeff's Shed that you had to have a full tank before you could enter, because it was less of a fire risk. The vapours are more dangerous than the fuel according to their insurance company. Link to comment Share on other sites More sharing options...
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