Old petrol

Due to family circumstances, I have had my Mk1 laid up in my garage for the last twelve months. During this time I have occasionally started the engine to let it warm up to operating temperature. Unfortunately this hasn’t been the case over the last four months although I did keep the battery charged up. 

Now that the family circumstances have eased somewhat I decided this week to take the car for a short run to test the brakes etc were OK. After starting the engine and starting to move off there was a lot of spluttering going on in the engine and oil splattering from the exhaust. I drove the car for about three miles in total and I persevered with the engine running until it was very nearly running as it should and took it back to my garage. The following day when I pushed the car out on to my drive I noticed that the engine had leaked some oil onto the garage floor overnight. The car engine fired up again and although it  ran it still didn’t seam to be as smooth running as it was before it was laid up. I believe, rightly or wrongly, that petrol can "go off ".

I would like to, if possible, to remove this old petrol myself and refill it with fresh petrol. In the meantime I have been speaking to a friend of mine who told me that he thought there was an additive that I could put into the petrol in the tank that would improve the petrol and enable me to save having remove this old petrol.

The question is, is there anyone who has had a similar experience with petrol and what they did to improve matters and does anyone know anything about this additive that I could use to save me having to remove the petrol from the tank?

Modern petrol does ‘go off’ as your friend said. Given long enough it will evaporate leaving a nasty gum like substance behind.

I had a case with a motorcycle with carburettors where I left it a few months over winter without starting it. It sounded like a tractor and ran unevenly when I used it next. After the carbs were cleaned out and new fuel was put in the tank it was fine. 

I think problems with fuel will get worse in the future as the amount of ethanol is increased.

With your car how much fuel is in the tank? Could you top it up with new petrol to dilute the old stuff?

You can get an additive that’s added to petrol to stop it going off, a quick internet search brought this up. Haven’t used it so can’t say if t works or not.

https://www.wynns.eu/product/fuel-stabilizer/

Years ago you could get a similar additive for lawn mowers to add to the fuel tank. If you get something make sure it’s not harmful to catalytic converters (assuming your car has one fitted).

Like Bannedbiker I have a carbed bike. My method with that is a squirt of 2 stroke oil in the petrol and as it has a tap, to turn it off and run the carbs dry.

 

Trouble is if the tank is empty then it will rust inside, bike or car. 

How much in your tank ?  If only a small amount then I would be sucking on a tube, part fill with new, then run till hot. Add the additive of your choice by all means.

 

If you do periodically fire it up then get it hot. I feel that a five minute run at tickover does more harm than good. Just my opinion mind.

 

 

Paul G

Yes petrol can go off over time, but with your sypmtoms I would pop opent the air filter box ain see if you have a mouse nest in there causing a blockage.  Also check no exhaust blockage.

 

My instant thought if you have oil leakage (on the garage floor) pop the plug leads off and have a look down the plug wells on the cam cover. A leaky cover gasket could lead to oil getting on the plugs/leads = lumpy running and also dripping down the engine and also from the CAS seal at the back of the engine. 

I’ve had the above myself and sorted with a new gasket. We’ll worth draining a full tank of old fuel or  if a small amount fresh fuel.

Thank you every one for your replies. I will first try to “suck” the petrol out with a tube if I can get a tube in there as I believe in modern cars you can’t, but mine is about 26 years old now so it may not apply. If that doesn’t I will pop into town to see about an additive, as we have a business called Motoscope who tune up posh cars etc and they may have it I am told.

I thought the additive was to stop the petrol degrading not to cure the problem after it had gone off. 

Get as much of the old stuff out (safely) and dilute whats left with fresh and sort the oil leak.

 

Richard. 

 

I think the obvious first step is to remove the plugs and check for oil on the threads, indicating cam cover gasket failure. An Italian tune up will sort the effects of this (but not fix the cause). Before you go poisoning yourself with this stupid sucking/siphoning petrol out idea, how about trying to drain the tank as Mazda intended, via the tank drain plug. You will need a new crush washer (can’t remember the size, but readily available at your local factors. And also check for mice etc in the intake. And fit a new fuel filter.

It doesn’t seam possible to get a siphoning tube into the tank from the filler cap end. I have read about the drain plug underneath the car from my car manual  and from the description, it could be difficult and expensive if the drain tap doesn’t open easily, as it may be damaged and will require a new tank to be fitted. This seams to be a dealership job rather than an owners job. So, bull by the horns, and I think I will fill the tank up with fresh petrol and hope that it will solve the problem for me on its own. I will let you know if I am successful or not.

Ps My garage doesn’t have mice or vermin in it, there are too many cats belonging to neighbours wandering about.

Where’s the oil dripping from?

 

I had no issues with the tank drain. Its only like a sump plug.

 

Again, check the plugs. And check the airbox at least, rather than blithely assuming all is well. These are all easy checks. Your approach is hardly bull by the horns as you avoid ignition checks.

Hi every one, I have done all of the checks you have suggested I should apart from removing the petrol from the tank, so I decided to fill the tank up with supreme grade petrol and then I took the car for a run of only five miles and it appears to have sorted the stale fuel out. I am about 95% certain it is OK, the only doubt I have is because I have only driven my Quasqai during the MX5 lay up, so it is a case of me getting used to the motors sound again. 

thanks again from every one who gave me there thoughts and ideas about what I should do. Next year may be the last year I keep the MX5 as I have just turned 84 years old on the 15th September. It is getting hard to work on the car now with all the problems age brings. 

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