Possible stale fuel

Ok , what are the symptoms of stale fuel, when I start the car up she is not firing correctly (only firing on three) , but after a revving it clears. The fuel tank is about half full now from over a year and a half from when it was last filled up. If the the opinion is stale fuel do I need to get it drained or would a full top up do

Regards John
stale fuel can give limp running due to poor burning but mixing with fresh ought to sort that. starting with stale fuel is difficult. ethanol making that much harder! we can add stabilisers in future to stop fuel going 'off' for a while.ideally store vehicles with full tank to reduce condensation /corrosion in tank. there are additives to fuel to boost burning rates eg octane booster.


Active Member
do I need to get it drained or would a full top up do
If that old and half full, I'd drain fuel the best I can and get a reasonable quantity of fresh fuel in to dilute what is remaining of the stale fuel.
If it's not too difficult, draining and clean the float bowls in the carb/carbs, this is worth the effort too. Do this after flushing the supply pipes.

At least the engine is running, the other option is just go for a long drive to use the stale fuel. But don't go further from home than you are prepared to push the car.... ;) Then fill up....

Good luck.


Well-Known Member
If it has stood that long there might be deposits condensed out of evaporating fuel in many places in the fuel system - some sort of flushing could help if the problem persists. Try adding some injector cleaner to the tank., but be ready to change the oil soon after. Easier in a car with EFI, as you can jumper the pump and have it circulate fuel through the excess return line - has worked for me.