Did a quick search and got tired of looking.

Filled my car up 1st Sept and had a tensioner failure the same day, now replaced the engine and ready for mapping Wednesday. I have less than a quarter of a tank as when fuel went crazy last month I syphoned most of it out to fill my mums car via the fuel filter as engine was out anyway.

Anyway, the point, the remaining quarter is now 3 months old, should I/would you:

A) fill her up with fresh fuel and wack some redex petrol booster in to account for any degradation
B) drain the lot and fill up with fresh

What stops me doing A is that it's being mapped on what's in the tank, what stops me doing B is having to break out a spanner again when the things finally back together lol. If B is neccesery I'll just do it via the filter again as pretty sure the blobeye tank doesn't have a drain but if needs must and all that.

 

If it was me, I’d either just fill it up with whatever fuel you want it mapping on. Or drain and fill.

wouldn’t bother with an additive

 

If it was me I'd just drive it with the old fuel till run down then refill....just drive easy on it

 

for me , drive easy till it’s nearly empty then fill
with what ever fuel you are mapping it for , it’s hard to say if the fuel has gone off in three months , but if it has then you will get a mixture of good and crap fuel for your re map , a remap is going to be better if it’s exactly what you will use long term ,


Generally speaking, petrol has a shelf-life of six months if stored in a sealed container at 20 degrees – or just three months if kept at 30 degrees. The more it's exposed to heat, the more quickly it will go off.17 Jun 2020
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https://www.rac.co.uk › know-how

Does fuel go off? Old fuel and fuel storage questions answered | RAC Drive

 

If that were me, for the sake of just a quarter of a tank i'd take it out and get some new stuff running thriugh the lines asap.

 

Exactly this.

Fuel does go off but it won't have gone off to such a degree that the ron rating is like 80 octane. Not in 3 months. But like others have said you want the fuel for mapping that ideally you will be using. You could drain the fuel but for the hassle thats involved, unless you have a pump etc just drive it around till its empty. Plus with a new engine in you're not going to be smacking it off the limiter.

Lets be honest that last quarter isn't a quarter, especially the way it goes through so quickly lol. You better not be doing the hose pipe and mouth method, thats dangerous. Plus all that back wash of yours contaminating the fuel . Its too cold o be doing that business any way lol.

 

I read about fuel shelf life, I imagine it has been below 20 with the cold the last few months and it's been in the tank so kinda sealed I guess but yeah it's not exactly precise, hence the doubt.

I can't drive it just yet, engine went sept, mot due Oct so sorn'd it, now a 2.1 but not yet mapped so can't mot it till it is. Having to trailer it there and get the mot a couple of days after.

I've been told I can let it idle no issue as all other parts have been mapped in previously so that's an option but no my other one wouldn't be a hosepipe haha. Had a friend do that in school 20 years ago during the petrol crisis, was on meds for years after he swallowed when a cop car drove past lol. I'd just unplug the sensor and undo the feed to the filter and crank it out.

 

In that case drain as much of the fuel as you can with your method. Throw in some fresh stuff and get it trailered to the mapping station. Your mapper shouldn't be mapping it to the point where you have no leeway any way. There is going to be some variance from forecourt to tank etc.

 

I've always left my cars with a full tank or at least some fuel for the winter storage and it has never been a problem with the fuel when it's been time to use the car again 6 months later. Unless it's been mapped on the absolute detonation limit it should be fine, especially if you can drive it without using full throttle. Then it won't matter at all.

 

Brim it with whatever you are going to get it mapped on

 

Plot twist: Winter petrol is different to summer petrol. So long as the fuel cap seals well (hisses when opening in summer), fuel should be fine if brimmed with fresh. My theory is you should map with the worst quality fuel to give safety margin for when you get a duff tankful.

Don't use octane booster/additive unless you intend to use it all the time.


Personally I also wouldn't let it sit and idle if its had new piston rings; It's usually advised to keep above idle, and vary the revs whilst loading the engine to bed them in.

 

Only difference is the fuel might have more water in it, as petrol draws water from the air. Wouldn't bother me.