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Fresh petrol in a lawnmower every season?

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kc04/02/2019 11:57:03
5954 forum posts
168 photos

When I bought a new lawnmower last summer the dealer went to great pains to point out it would need to go back to him every Spring to be serviced and have the old petrol changed. He mentioned petrol nowadays has increased amounts of stuff added which deteriorates over time. This seemed logical until I thought about it and wondered what he did with all the petrol he drained out of all those lawnmowers! As it's difficult to just throw away I decided he probably just put it in his car! Probably just mixed the old with plenty of new petrol.

So what do forum members do - especially the people who use ride on mowers for the club field - do you just drain out the old and eventually put it back in the mower mixed with new? Or is it just a dealers tale?

Ron Gray04/02/2019 12:09:21
1429 forum posts
359 photos

I’ve never bothered about the age of petrol I use in my petrol mowers, however draining the fuel at the end of the season and using additives such as Sta-Bil helps matters.

Ultymate04/02/2019 12:27:53
1693 forum posts
57 photos

I would advise not draining the tank completely but run or drain it to a low level for the winter and then refuel for the spring when the new fuel will mix with what's left of the old the old. I'm a lucky son of a gun as I use my mower (ride on) as tractor pulling a trailer for our logs in the winter, and I also use the petrol mix for my models in my chainsaws for the winter. It's mainly a case of unleaded petrol slowly losing it's ability to vaporise over long periods

Edited By Ultymate on 04/02/2019 12:28:44

Jon - Laser Engines04/02/2019 12:36:37
4766 forum posts
179 photos

modern fuel has ethanol in it and this can rot the innards of the carb if left for long periods. Fuel also goes off after a while anyway so its probably best to run the engines dry over the winter or use ethanol free fuel.

Former Member04/02/2019 12:43:41
724 forum posts

[This posting has been removed]

Piers Bowlan04/02/2019 12:58:30
1825 forum posts
44 photos

I have never bothered to drain old fuel in either my Westwood ride-on or small Hayter petrol mower and not experienced problems starting them. If you do have trouble starting, trying some fresh fuel would be a good idea after you have have cleaned the spark plug and checked the ignition first. Draining fuel from the carb can be a good idea to prevent it getting blocked with varnish-like residue once fuel has evaporated but then again the carb diaphragm can dry out and harden/crack without fuel, so that is not so good either! I usually use my mowers to clear leaves in the winter rather than leave them for months without running, so maybe that is why I haven't had issues with stale fuel.

I have found that mower servicing can be an expensive luxury if you have the time to do it yourself. Clean the plugs, change the oil, clean the air filter and check the tension of the belts. Other than generally cleaning and lubricating it, all in all it is not exactly rocket science. My Hayter 41 is still going strong after 20 years.

Just my 2p worth.

Edited By Piers Bowlan on 04/02/2019 13:24:27

Mike Etheridge 104/02/2019 13:24:51
1509 forum posts
408 photos

When I bought my 4 stroke petrol mower a few years ago the salesman suggested I use specialist petrol 'Aspen 4'. It claims on the plastic container that the fuel is free from Sulphur, Benzene ,and Aromatic Hydrocarbons and it's use means that the mower would require less maintenance. Certainly it appears that the spark plug does not soot up as much as it did in the past with standard petrol in my old mower. The new Chinese mower however is a pig to re-start when hot so I have to try to mow the whole of the lawn lawn prior to emptying the grass box which means I have to keep the grass very short. I wonder if the Aspen fuel which I have seen for sale in Garden centres would have any advantages for petrol model plane engines ?

Frank Skilbeck04/02/2019 13:25:24
4430 forum posts
101 photos

A fellow club member has a plug in hybrid car, which he runs entirely on battery power for all his journeys, the other day it started to use the engine and a message came up that the engine was running because the fuel was getting old and needed to be used. He had filled it up several months previously and now it wants to use the fuel before it goes off.

BTW on our club mower we never drain the fuel and do our own servicing on a basis of "maybe it needs servicing now" the engine is still running fine, but the cutting deck, pick up and hydrostatic gear box are getting very tired, not sure if draining the petrol every year would have helped.......................... (BTW the mower is over 15 years old and kept outside)

Percy Verance04/02/2019 13:28:23
8109 forum posts
155 photos

No need for fresh petrol each time. Just use fuel stabiliser in your petrol. Lots of different brands. Briggs & Stratton do one. It's available on Amazon and at mower/chainsaw outlets......


Aspen is odour free, and so ideal for those whom feel sick after sniffing petrol (me). It also has the advantage of not going *off*. It isn't cheap though........ I think it's obtainable in both 2 and *straight* four stroke mixes.





Edited By Percy Verance on 04/02/2019 14:00:43

john stones 104/02/2019 14:21:21
10490 forum posts
1475 photos

Dealer wants your money for servicing it, it's a garden mower, do it yourself.

Ron Gray04/02/2019 14:26:21
1429 forum posts
359 photos

Slightly off topic but raised by MikeE above - Aspen in our gassers - wait for Jon to bounce back on this as I know he favours it if only because it doesn't smell like petrol does!

Don Fry04/02/2019 14:48:06
3822 forum posts
42 photos

My outboard maker, Mercury/Mariner, 4 stroke and 2 stroke, says in their instruction, to use modern petrol within a month. The methanol content causes water to get absorbed into the petrol, same as old glow fuel. I keep a bit of 98 RON petrol, for use at the end of a season, so what is left over the winter has no ethanol n it. And having seen carbs gunged up with old standard petrol, the salesman isn't lying, just not telling how to avoid problems.

I'm tight, and use cheap petrol when I can. Easiest way is use 98 RON on small motors and occasional use engines.

John Duncker04/02/2019 14:56:00
79 forum posts
7 photos

Petrol with ethanol in it does go 'off'. with time.

So if it were mine I would run the tank low and the carb dry before storing it for the winter. Top the tank up with fresh fuel in spring and good to go.

Petrol with ethanol and mixed with 2 st oil is bad news if kept for more than 6 months. Even if you drain the tank dry and empty the carb the residue seems to cause some sort of crystals to form and these block up the carb jets.

I don't know of any magic nostrum that works.

Peter Miller04/02/2019 15:16:39
10067 forum posts
1192 photos
10 articles

I am afraid that I just leave my mower as it is. IT starts in a couple of pulls next spring.

Much the same applies to the big club Mountfield and that has been running for about 7 years now

Engine Doctor04/02/2019 15:29:53
2267 forum posts
25 photos

You can add a dose of Fuel Fit also called Advanced fuel Aditive , its made /sold under Briggs and Stratton specifically for that reason . Apparently the US has 10% Ethanol ,almost double the ethanol that we have in our petrol so it is a real problem . We will be following the US soon I believe probably due to the cost effectiveness of adding ethanol but we'll be told its to do with pollution no doubt ! The fuel safe floats on top of the petrol and stops the contents oxidising during lay up time. It also according to the blurb reduces corrosion of carb parts . I tried mixing it with our methanol fuel . It didn't have any noticeable effect on running of the engine that I could detect but haven't tested to see if it could protect bearings against corrosion .

Edited By Engine Doctor on 04/02/2019 15:39:19

Kim Taylor04/02/2019 15:43:38
274 forum posts
53 photos

I've said this previously on a similar thread, but petrol does go 'off' and sometimes quickly at that!

In our 2 stroke karts 'back in the day' we would use fresh fuel every meeting - if we tried to use fuel only 2 weeks old, it would cause the engine to misfire under load. Mind you, we were running them up to 22k rpm, so a high stress environment.

In my generator, in contrast, I never change the fuel. The engines will more or less run on anything, as long as the carb jets aren't gummed up.

I use Aspen fuel in my petrol model as I can'r stand the stink of petrol either inside my car or in the spare room where I store my models.

As an off topic aside, to get rid of the old 15:1 caster mix we used in the kart engines, I used to put the remnants (usually a gallon or so) in to my car when I filled the tank.

The car developed a knock in the engine whilst within warranty, so was sent in for investigation. After a day or so, I got a phone call from the garage enquiring if I'd been using any additive in the petrol, as the piston rings were gummed up!! Of course, I denied all knowledgeembarrassed.................


Fatscoleymo04/02/2019 16:40:49
243 forum posts
86 photos

I've never had problem in 14 years leaving petrol in over the winter in both ride on and hand mowers - they start ok in the spring. But I have had a problem twice when the ride on was left with an empty tank and the feed hose dried out, cracked and had to be replaced. No other fuel related issues at all. Plenty of others though...

Trevor04/02/2019 16:45:59
365 forum posts
52 photos

Ditto. We have an 18 year old ride on which has never had any additives or fuel draining treatment. It was serviced last year (after an 8 year gap!) and the mechanic said it was still in excellent condition. I have no doubt that petrol does go off as others have described but in my experience a Briggs and Stratton engine is more than capable of running on 6 or 8 month old fuel without a problem.


Jon - Laser Engines04/02/2019 16:51:49
4766 forum posts
179 photos
Posted by Mike Etheridge 1 on 04/02/2019 13:24:51:

I wonder if the Aspen fuel which I have seen for sale in Garden centres would have any advantages for petrol model plane engines ?

Yes, the advantages are numerous and well worth it. I will be recommending it as the best fuel for our petrol engines if i am ever able to get them out there.

I know people will complain its more expensive than petrol, and that is true, but to me its worth every penny not to have to deal with the stink, and its also much better for the engine.

kc06/02/2019 12:12:35
5954 forum posts
168 photos

Thanks for all your comments - they confirm what I thought. In a couple of weeks time I will just see if the mower starts with a bit of fresh petrol mixed in after it's 3 month layoff.

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