Are you talking about a fuel stabilizer? Yes, it's good to use one, but it will not cause a new mower to not start if you don't. Possibly your fuel is old or contaminated with moisture? Are you sure it's not out of gas? Have you checked the oil? Is it a Briggs & Stratton engine? Some mowers with this engine have been experiencing the same thing, and I don't know if the cause is known yet. If you have fresh gas and can't get it started after reviewing the instructions in the owner's manual, you may be forced to return it or get warranty service.

Which specific additive?????

if the "additive" is 2 stroke oil, then the mower is likely toast. if it is not, then maybe you just have bad gas/dirty carb?

jillian; in the other thread you started on this, you state it is a 'Briggs' engine, so no 'additive' is required. If this is one of the new Lawn-Boy mowers from Home Depot, I think this engine has some kind of fault in the cold-enrichment system (choke) so it will be very hard if not impossible to start. Wherever you got it, assuming it's new, take it back and tell them to fix it.
Although not required, you will find that use of Sta-Bil in your gas can every time you go to fill it will prevent many problems over the years.

I use the blue sta bil in my gas cans. It keeps the ethanol from separating
and growing stuff in it.

"I use the blue sta bil in my gas cans. It keeps the ethanol from separating and growing stuff in it."

I see these posts all time and find them very strange. I never put anything in my gas, I store whatever is left over the winter in the gas can AND leave whatever is left in my gas tanks at the end of the season and I never have any trouble with anything "growing stuff". I have one pc. of equipment that is only run once or twice a year and it doesn't even bother.

Walt Conner

What kind of stuff could possibly grow in gasoline??? Gasoline has to be one of the most inhospitable environments for animal or plant life to grow in I can think of.

'I use the blue sta bil in my gas cans. It keeps the ethanol from separating
and growing stuff in it.'

Me too. For the areas where only E10 is sold, you really need something in the fuel to protect the fuel system parts from corrosion and the fuel from degradation. And, it offers many benefits for non-ethanol gas too.
As far as 'growing something' I'm sure that was 'tongue-in-cheek'. I don't believe the ethanol 'separates' from the gasoline, but any time you have alcohol in fuel, you also potentially have moisture. The combination of moisture and alcohol make a corrosive solution. Many manufacturers now recommend fuel additives to prevent damage from alcohol fuels. I first saw this in the Honda engine manual for one of my mowers.
My current brew is the recommended 1 oz/ten gal of Sta-Bil Marine for Ethanol plus 4 oz MMO for my vehicles and OPE. I've been using this for several years and everything I have seems to love it.

The original poster has not bothered to offer additional information information about the mower in question. We have no idea what kind of "additive" or how much was used. In a 4 cycle engine, no additive is "required", but too much of any additive would be bad. Come on, original poster, and give us some information so we can speculate further.

I saw this first hand in the tank for my boat. I did not use any stabilizer over one winter and the ethanol started to separate from the gas. Once condensation entered
the tank it it started to grow some stuff in the layer between the water and the ethanol. Since ethanol is corn based there is something that grows in that layer.
Also, ethanol is killer on the older rubber hoses and plastic tanks.It will start to degrade the inside of the rubber and plastic and becomes gummy.
Once that is in the carbs it is a PITA.
Now this was in a boat and not a mower but I am sure the same can happen in anything.

"Me too. For the areas where only E10 is sold, you really need something in the fuel to protect the fuel system parts from corrosion and the fuel from degradation."

That is all that has been available in this area for a number of years and I stand by above post.

Walt Conner

After spending over $1000 to have the fuel lines replaced and 4 carbs rebuilt and synced and the exhaust ports cleaned in the outboard i will continue to use my blue sta bil n all my power equipment. just cheap insurance on my part.

Walt: I'm not seeing this as an argument, only people stating what they use or don't use and why. Bottom line, it's whatever works for you. To the original question by 'jillian', she must be referring to fuel stabilizer. I cannot remember reading a single post on here where anyone said it was mandatory to use it, and if you didn't the engine would fail to run. Personally I wouldn't be without it, but that's just me. I'm sure there's a systemic problem with some new B&S engines in the cold enrichment area that is making them hard to start. B&S and Toro really need to get all over that. I'm sure we've all seen all the cold-start devices they've come up with over the years, but in my book it's still hard to beat the old B&S 'classic' spring-loaded choke plate. It not only provided enrichment for starting, but also when RPM would drop under sudden load which helped the engine recover, and it was completely automatic.

saxman1, I am not arguing with anyone, I am just stating my experience with gas and I am puzzled by all the commotion over ethanol. The indication seemed to be that I was not using ethanol and I was setting that straight. If you don't happen to like what I say, don't read it.

Walt Conner

There are geographic differences involving gas degradation and carburetor problems. I have personally seen green stuff grow in dozens of carbs in certain areas and not so much in others. I do not use stabilizer either and seldom experience problems. I just started a Lawn-Boy that had been sitting 3 years. Didn't drain the gas and it ran good. I do think ethanol might degrade the plastic fuel lines and bulbs though. I've had a lot of failures of those lately.

Hey Walt; why don't you take another 'vacation' from this board if you can't keep your shirt on?

Actually I am going to do that but not because of your suggestion. After all, you are the one who felt the need to call me out by name as though I was being argumentative and this wasn't the first time. Don't know what your problem is but hope you get better. As I said before, if you don't like my posts, don't read them.

Walt Conner

Hey Walt. Why don't you go to China?