How old it too old for petrol/gasoline in the car - and can I damage it?

Hi,

I have been using my 1993MY 3.2 litre Sovereign shamefully little of late and the fuel in my car is now rather old. By my reckoning the majority of it is at least 3 or 3.5 years old.

I freshened it up last year with some new petrol and drove it out for its MOT test without an issue last year, but only drove it a couple of times. A year on is it now likely to cause me problems and possibly even damage the car?

The fuel I likely used is Shell V-Power which is no more than 5% ethanol.

David

Hard to say but I would dump it. If it smells off definitely don’t use it. I had valve failure using just a little bit of old fuel, 1:40 or so, although that fuel was much older. Not worth it.

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Why take the risk ? Petrol goes bad at different rates depending on lots of factors like climate and storage conditions, at 3.5 years old and stored in a regular car tank the chances are it is well past it’s best, even if it smelt ok you couldn’t be certain it still had the same octane level. I would syphon off as much as I could before putting fresh fuel in. I always use Shell V Power myself so I know it’s not cheap ! But if you damaged the engine or fuel system it would be a whole lot more expensive.

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By this reckoning me dragging a petrol car out of a thicket after 10 years layup and trying to start it should have blown the engine to bits on the first turn of the key, but guess what, it didn’t.
Petrol is no longer petrol, but mainly additives, which evaporate in time, so the fuel loses combustibility and energy content.

I’ve yet to see a YouTube video where a car that won’t run because it has old “gas”, then runs after new fuel is put in.

My advice, from my experience, is to either give it a whirl, or shove a gallon of fresh petrol in, then give it a go…it’ll either run or not.

What was the failure?

The high varnish content gummed up the intake valve stems, which was not a problem until the engine had time to fully cool down. I had to drift them out with a large hammer. No big deal for me since I got to inspect how my first ever engine rebuild was keeping up after a few thousand miles, and was back on the road after a few days, but not recommended.

I just thought the best way to get rid of the old fuel was to mix it in in small quantities. It was probably 50 years old and the tanks were still full, about 75% maybe. Ran great.

It is probably still good but sometimes fuel starts to deteriorate after half a year. I‘d like to give different advice but I can’t, it’s just not worth the risk.

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my old fiat 500 restarted after 7 years of stop, with the fuel that was inside the tank… then i went to a gas station topped the gas tank and went directly to the mot… so it depends…

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I don’t think anyone has suggested using old fuel would ‘blow the engine to bits’ if you tried to start it. The risk is the fuel has degraded and lost volatility so the engine won’t run well. It could gum up the injectors, cause pre -ignition and pinking under load and other potential issues, why risk that for the sake of saving a few quid. I’ve started lots of cars in the past with old fuel in the tanks, sure they started ok, but they didn’t run very well until the old fuel was replaced with fresh fuel.

I must admit I am a little nervous of the fuel being so old. Has anyone got any experience of these companies which drain the tank after misfuelling?

I have but I just re-read that not even all of the fuel is three years old. I think it should run well but to be safe I would drive down the filled up tank and refill (with E10 which might help with the moisture if it had time to collect) before leaving it for the night. It might run worse but it is really unlikely that it grenades the engine!

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What about throwng a bottle of octane booster in it if you are concerned about loss of octane, with the possibility of water in the petrol throw in a litre of methylated spirits, that will mix with both any water and the petrol.

Don’t waste coin on octane boosters, if you’re concerned about octane depletion just throw a half pint or so of kerosene in the tank when you top off. High octane gas is significantly less volatile than regular BTW.

The light components evaporate first and octane rises, but it is harder to ignite. Neither will be a problem. No octane booster needed, although I‘m not against using alcohol to get any water out, probably not much of an issue in a modern car like the xj40?