AR15.Com Archives
 Will a 4-stroke gas generator run on 2-stroke oil premixed gas?
WS6_Keith  [Team Member]
10/16/2008 2:59:16 PM
I've been thinking about getting a generator for the house, but fuel storage is a problem. Between my 2 boats, I do have the ability to store around 180gals of fuel, but they both have 2-stroke motors which require me to pre-mix the fuel with oil.

Will a generator 4-stroke run on pre-mixed fuel without issue?

I'd really love to have a diesel genny, but those are out of my budget range.
TeeR  [Team Member]
10/16/2008 3:27:37 PM
without issue.... no .... the oil will effect the plug before long. But it will run and smoke like hell.
Growler67  [Member]
10/16/2008 3:39:36 PM
Depending on how thin the mix, you may not even get your 4 stroke to fire. Changing to hotter plugs may help, but eventually they too will foul. If you get it fired and it runs, then as stated above it will smoke like a MF'er. A multi-fuel engine might do it with little if any adjustment. However, those are even more expensive than diesels. For the eventual maintenance headache, I wouldn't do it. In an emergency, sure, emergencies are emergencies. As practice, you will be creating more problems than you would be solving.
dablues  [Team Member]
10/16/2008 4:12:18 PM
I've run two-stoke mix in a pinch. My guess if you switched to fully synthetic 2-stroke any problems would be minimal.

A buddy was given an old lawn mower by his dad. His father is a licensed mechanical engineer - so he should have known better....anyway, he tells his son "This is one of those two stroke engines, so all you have to do is mix oil and gas and you'll never have to do anything else."

The punch line is my buddy was showing off his hand-me-down mower - and the engine says "Briggs and Stratton" !

The old guy had run this 4 stroke engine mower for ten years on 2-cycle mix and had never added a drop of oil to the crankcase. I poked a stick in the crankcase and all there was in there was about 1/8 inch of black goo. All that was lubing the crank was whatever oil mist in the blow by. It did have a bit bit of rod knock, so we filled the crankcase and my buddy used it another 3 years.

Moral of the story...Briggs and Stratton engines are pretty durable and 2-stroke mix will burn.

Worst that can happen is you'll foul a plug. Give it a trial run and see how it works?
CLICKBANGBANG  [Member]
10/16/2008 5:35:31 PM
will not work. single cylinder might not even idol. yes on the smoke. as soon as your frig, well, micro, even a coffee maker, or any thing else that pulls any amps kicks on it will die. i have seen 2 stroke put in a koler on accident (i think the same moron put kerosene in it too). it would fire while the cord was being pulled but the timing is so far of from a 4 to a 2 stroke it would not run. the motor itself is not made for a fuel that burns that slow.

but after all that, i would still try 2 stroke it a gennie if there was shtf spot where i had to have juice.
Justin-Kase  [Team Member]
10/16/2008 5:35:47 PM
You won't burn 180 gallons of mixed gas in a 4 stroke gennie without a lot of work changing/cleaning plugs and maybe cleaning out the carb. I'd try a different approach.
TheOtherDave  [Team Member]
10/16/2008 5:41:30 PM
The jetting will be a little lean with the 2 stroke mix. Lean enough to matter? I dunno.
DanishM1Garand  [Member]
10/16/2008 5:48:31 PM
I have used 2stroke gas at 50:1 in a mower without even being able to tell the difference. I quit using straight gas when I cut yards to simplify the supplies carried. Good 50:1 oil will work in your boat and genny.

YMMV though.
WS6_Keith  [Team Member]
10/16/2008 6:20:08 PM
Well, up to 150gals would be 50:1, the last 30 would be 32:1. Maybe I should just hold out for that diesel genny. ;)
rippler  [Team Member]
10/16/2008 6:24:35 PM

Originally Posted By DanishM1Garand:
I have used 2stroke gas at 50:1 in a mower without even being able to tell the difference. I quit using straight gas when I cut yards to simplify the supplies carried. Good 50:1 oil will work in your boat and genny.

YMMV though.


Ever since the sil used straight gas in the weedeater all I kept around was gas mixed 40:1. The 8 yr old lawn mower never noticed.

I ran a tank thru the generator (11 hours) after Ike last month and it didn't notice either...still starts on the first pull.
JakeThePimp  [Team Member]
10/16/2008 6:40:45 PM
It ran fine in my 14hp kohler lawn tractor. I needed it in a pinch, about a 1/2 hour worth of work. No issues whatsoever other then the exhaust had the smell of two-stroke.

If you think about it, it burns the same in a two-stroke AND lubricates the crank. The only thing I'd think it could mess up is the intake and exhaust valve, possibly the spark-plug.

-JTP
batmanacw  [Team Member]
10/16/2008 6:53:20 PM

Originally Posted By TheOtherDave:
The jetting will be a little lean with the 2 stroke mix. Lean enough to matter? I dunno.

this...

It will not be good for the motor, especially under load.
ColtRifle  [Member]
10/16/2008 6:57:12 PM
If it's 50 to 1 mix, it won't hurt a thing. If it's mixed with much more oil, then it will still work just fine but will smoke a little...or a lot.

It won't hurt anything in spite of what some people are saying here.

I would not burn it in a modern car engine because you will foul the catalitic converter and the O2 sensors.
kevthebassman  [Member]
10/16/2008 7:08:24 PM
How about filling the boat tanks with regular gas for storage. Before you take the boat out, put the oil in the tank before you hit the road. If you've got any distance to drive at all, the sloshing around in the tank should mix it just fine. You might want to put a tag on the boat key before you store it so you don't forget to add oil.
PromptCritical  [Team Member]
10/16/2008 7:11:32 PM
Guy I know was mowing his grandmothers lawn a few years ago.

Next-door neighbors were a bunch of hippies and gave him shit about using a gas mower.

Grandma told him he would be wouldn't be able to go out if he didn't get the lawn mowed.

The hippies were pleased when he ran out of gas.

In order to preserve his evening, he frantically searched the house for something to put in the mower.

He found a bottle of radio controlled airplane fuel.

He said it ran like a raped ape, screaming and knocking, and putting out enough smoke to blot out half the block.

The hippies were not amused.

Omni  [Member]
10/16/2008 7:49:54 PM

Originally Posted By PromptCritical:
Guy I know was mowing his grandmothers lawn a few years ago.

Next-door neighbors were a bunch of hippies and gave him shit about using a gas mower.

Grandma told him he would be wouldn't be able to go out if he didn't get the lawn mowed.

The hippies were pleased when he ran out of gas.

In order to preserve his evening, he frantically searched the house for something to put in the mower.

He found a bottle of radio controlled airplane fuel.

He said it ran like a raped ape, screaming and knocking, and putting out enough smoke to blot out half the block.

The hippies were not amused.






Funniest thing I have read all day.
storminnorman  [Member]
10/16/2008 8:51:21 PM
I've done it many times without a problem.