autojack Posted 29December, 2022 Report Share Posted 29December, 2022 At the start of a long home renovation project, I moved my 911 to temporary storage, which I expected to last about 9 months. At that time I filled the tank to full, and then added fuel stabiliser. This car has a Steve Wong chip with a fuel map for 95 octane and right after I filled the tank, I realised that I had put in 91. Since I wasn't going to be driving it, I left that problem for Future Owen to deal with. It's now about 18 months later and I'm finally ready to bring the car home and put it in the new garage, but I have two potential issues. First, the fuel stabiliser says it's good for 12 months, and it's already been longer than that. The tank is a bit more than 3/4 full, and it's going to take awhile for me to run through the rest of it. What I've read online seems to say that you can't just add more stabiliser to the same tank of petrol and have it keep working. Second, the octane rating of the petrol I put in is too low, and I've also read that this may reduce further over time. Having said that, I've driven the car a few times since it was parked and not noticed any knocking, although I wasn't flooring it or anything. So, what should I do? I could add octane boost now to take care of the low octane rating. I think I'm leaning towards doing that, and then just trying to run down the remaining petrol as soon as I can. It wouldn't do any harm. But I'm not sure if there's anything else I can or should do. Quote Link to comment Share on other sites More sharing options...
911 Posted 29December, 2022 Report Share Posted 29December, 2022 Smartest and easiest thing to do would be to dump the fuel, add some new fuel with a jerry can and add a good engine cleaner in like either Nulon, or Liqui Moly. You could just put an octane booster in and start the car and it might be fine, it may not. If it was my run around, which I don't care too much for, I'd do that. In my 911, not a chance. I'd go with option one. Why roll the dice when dumping the fuel and starting fresh isn't a massive job to begin with. Quote Link to comment Share on other sites More sharing options...
LeeM Posted 29December, 2022 Report Share Posted 29December, 2022 No idea if 98 is any different, yet as mine hasn't been started in 18 months (yeah yeah, I know 🙄), Porsche specialists Buik Motorworks told me to not risk it and dump the fuel. Quote Link to comment Share on other sites More sharing options...
Joz Posted 29December, 2022 Report Share Posted 29December, 2022 Replace the fuel, for a hundred $$ it’s the cheapest peace of mind. Quote Link to comment Share on other sites More sharing options...
Mezger Autosport Posted 29December, 2022 Report Share Posted 29December, 2022 Pull the fuel sender out and take the sniff test, and see if the fuel is stale, as a start. If it is and you can’t jack the car up, buy a suction pump with tank and simply suck the old fuel out, then re fit the sender. P-Kay 1 Quote Link to comment Share on other sites More sharing options...
Zelrik911 Posted 29December, 2022 Report Share Posted 29December, 2022 Drain the tank (underneath) and remove and inspect the Fuel Tank Strainer for any particles &/or water. There is something different with 'new' petrol as it doesnt last very long - my friends with prewar cars are having lots of issues when they leave petrol in tanks for long periods. Quote Link to comment Share on other sites More sharing options...
autojack Posted 29December, 2022 Author Report Share Posted 29December, 2022 Thanks for the suggestions so far. I should say that I already drove it for 30 minutes yesterday and it ran absolutely perfectly. That was before I realised that I couldn't just add more stabiliser to it until I finished off this tank. I wasn't expecting everyone to suggest dumping the fuel, but I can understand wanting to be cautious. Still, it's 70 litres' worth, and I'm an hour from home without any tools (at our holiday house, going home Sunday). I could do it, but... I'm more inclined to take it on several long drives and use up as much of the petrol as I can, and then refill it. Joz 1 Quote Link to comment Share on other sites More sharing options...
P-Kay Posted 29December, 2022 Report Share Posted 29December, 2022 Me....I'm in the drive it and don't thrash it camp. It still combusts, therefore as long as you drive sensibly, then how much harm can it really do? Perhaps I'm just an ignorant, but that works for me Quote Link to comment Share on other sites More sharing options...
autojack Posted 29December, 2022 Author Report Share Posted 29December, 2022 21 minutes ago, P-Kay said: Me....I'm in the drive it and don't thrash it camp. It still combusts, therefore as long as you drive sensibly, then how much harm can it really do? Perhaps I'm just an ignorant, but that works for me Well... It could gum up the whole fuel system, and cause excessive crud to accumulate on the valves. I'm not trying to be cavalier about it, and I'm usually pretty paranoid. But dumping it feels unnecessary in this situation. I'd be more inclined to do that if it hadn't had any stabiliser in it this whole time. Quote Link to comment Share on other sites More sharing options...
P-Kay Posted 30December, 2022 Report Share Posted 30December, 2022 Fair point, and it all boils down to individual risk tolerance. For me, it's been months not multiple years plus you added the stabiliser. 11 minutes ago, autojack said: Well... It could gum up the whole fuel system, and cause excessive crud to accumulate on the valves. I'm not trying to be cavalier about it, and I'm usually pretty paranoid. But dumping it feels unnecessary in this situation. I'd be more inclined to do that if it hadn't had any stabiliser in it this whole time. Quote Link to comment Share on other sites More sharing options...
3legs Posted 30December, 2022 Report Share Posted 30December, 2022 I'm about to do the same with my Boxster which has been sitting for around 18 months as well but I only have about a 1/4 of a tank of fuel. If I just fill it up with new fuel and let it mix with the old fuel would that cause any issues? Quote Link to comment Share on other sites More sharing options...
Peter M Posted 30December, 2022 Report Share Posted 30December, 2022 I think everyone's overthinking things. Just top up your tanks with your usual fuel and just drive. 3legs, Rob, Joz and 1 other 4 Quote Link to comment Share on other sites More sharing options...
Rob Posted 30December, 2022 Report Share Posted 30December, 2022 2 hours ago, Peter M said: I think everyone's overthinking things. Just top up your tanks with your usual fuel and just drive. Absolutely Peter - driving normally without trips to the redline will use the problematic fuel without harm. And where do you "dump" 70 Litres of fuel? 3legs and Peter M 2 Quote Link to comment Share on other sites More sharing options...
OZ930 Posted 30December, 2022 Report Share Posted 30December, 2022 6 hours ago, Rob said: And where do you "dump" 70 Litres of fuel? If it’s 98 then put it in a car that doesn’t need 98 or lawn mower, whipper snipper…two stroke engine, don’t forget to add oil. Quote Link to comment Share on other sites More sharing options...
mc968cs Posted 30December, 2022 Report Share Posted 30December, 2022 I suggest drive it on 1/2 throttle max. Ie; just use the fuel up. Quote Link to comment Share on other sites More sharing options...
Peter M Posted 30December, 2022 Report Share Posted 30December, 2022 On 31/12/2022 at 05:28, OZ930 said: If it’s 98 then put it in a car that doesn’t need 98 or lawn mower, whipper snipper…two stroke engine, don’t forget to add oil. If I was feeling I should reuse the fuel in something else, I'd only reuse in something that is known to be easy to start like my wife's car rather than lawn equipment as old fuel can cause hard starting when cold. However, leaving the mower in the sun for an hour before trying to start does work wonders when the fuel's a bit stale! As for changes in octane and increases in gum deposits, I think that is less of a problem for our likely circumstances than possible effect on cold starting and running: Aging effects on gasoline–ethanol blend properties and composition - ScienceDirect (Whilst this is looking at the effects of storing E25 up to 6 months, it's easy to read and gives some real comparative numbers that show many effects are relatively small) Liquid Fuel Ageing Processes in Long-term Storage Conditions | IntechOpen (See Section 4.1 and Conclusion. This paper looks at the effects of storing various fuels up to 4 years. I found it interesting that all the petrol samples still met the original RON octane requirements but not the MON.) I'm sure there are more specific scientific papers out there but the above are free! The technical info on the various fuel suppliers websites tends to be a very conservative "we can't guarantee it after 3 months so replace it" default position. Quote Link to comment Share on other sites More sharing options...
vl gra Posted 1January, 2023 Report Share Posted 1January, 2023 I would be driving as is. I would be putting some fresh 98 in as soon as possible ie: don't wait till empty tank. Quote Link to comment Share on other sites More sharing options...
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