The Triumph Dolomite Club - Discussion Forum

my 1500 fwd has had a tank full of leaded petrol in it since it went out of fashion. it hasnt gone like jelly, its still in a liquid state (i looked in the tank) but am i best to drain it out and replace it with unleaded - if so what additive to i put in with the unleaded fuel and in what amount. thanks

If it ran on leaded for long enough it will probably run fine on unleaded for years, UNLESS new valves have been ground in.
My Spitfire 1500 has run for about 7 years on unleaded without additive and without any signs of valve recession.

TL;DR: I would use up the 4*, petrol is too expensive to waste!

Cheap supermarket petrol from the 90's could evaporate in the carbs and leave a sticky deposit, however, if you had a full tank of 4* BP from 1998 in your tank for the past 20 years then the likelihood is that it's perfectly fine. Petrol in a sealed container or with a small volume breather will last indefinitely. Does it lose its power? Well I guess if ethanol was present it would evaporate far faster than petroleum would and so reduce the RON ever so slightly, doubt it would be noticeable. The jelly thing, you're entire tank wouldn't turn into jelly but some may form, caused by ethanol separation from the petroleum and because ethanol is hygroscopic it draws in water from the air and you end up with a squishy jelly like gunk either floating about in the tank or left behind in a carb bowl.


Edit: Couldn't leave it there with my pseudoscience opinion, went and looked it up. First document I hit was from BP who says petrol will only last about 3 weeks without fresh needing to be added, I don't actually fill my tank up that often, lummy...

https://www.bp.com/content/dam/bp-count ... -tanks.pdf
https://www.bp.com/content/dam/bp-count ... ndling.pdf

If the fuel has gone off? it will smell like white spirit or turps

Tony.

dollyman wrote: ↑Sat Jun 23, 2018 10:41 pm If the fuel has gone off? it will smell like white spirit or turps

Tony.

That makes sense, if the volatiles (eg butane) are the first to evaporate then I guess you end up with something more like paraffin than petrol!

Yep, give it the sniff test. How will you know it's off? You will, trust me!
Now a controversial bit - take a teaspoon of the old fuel, put it in a large outdoor space, make absolutely sure you don't have any spillage on or near you, and throw a match on it. If it goes up, it's good. If it does nothing, it's goosed.

thanks guys if it has gone off would it effect the running - a couple of people ive had round to look at it recon its running on 3 cylinders -
could that be to do with the 'old'fuel

wellskint wrote: ↑Sun Jun 24, 2018 12:25 am thanks guys if it has gone off would it effect the running - a couple of people ive had round to look at it recon its running on 3 cylinders -
could that be to do with the 'old'fuel

If it IS only on 3 pots, the problem is almost certainly not a fuel issue, but electrical or compression related.

Steve

I'd just keep topping it off with new stuff, if it's burning then you might as well use it..

My 1850 had half a tank of fuel in it from 1992 when it went off the road. I took the gauge sender out of the top of the tank and had a look inside with a flashlight. All looked well with no obvious crud or corrosion, and it smelt strongly of petrol. So I went ahead and started it without any bother on this old 4-star fuel. I have heard of taking a few millilitres of the fuel and dropping it on a warm paving slab. If its any good it will evaporate quickly with no residue.