Gas-oil mixture

I have several lawn-care tools that use a gas-oil mixture. Although I try to mix it in small quantities, sometimes at the end of the season there is some left. Is it safe to use what’s left in a car, or would the two-cycle oil damage something?

Back in “the old days” many of us used to add top oil to our gas tanks periodically to help lubricate the valves. This also helped to prevent “pinging” in engines that were prone to this problem.

Gasoline with a miniscule amount of 2-cycle oil added to it is essentially like a dose of top oil for your engine, and will not harm the engine in any way. I would just caution you to add only a gallon or so to each tank of gas, so as to avoid problems with the catalytic converter. Large amounts of oil burned in the engine can foul the cat converter, but by using a gallon or less per tank of gas you should not be causing any cat converter problems.

I’ve never had a problem keeping gas fresh from fall to spring with fuel stabilizer.

In theory you should be able to burn it off in the car, but the car has complex pollution controls. I suppose that you could maybe, just possibly, damage a sensor or something. Why not burn the stuff off in your lawnmower instead? It’s less likely to fail and cheaper to repair. That’s what I’m doing with last winter’s snow thrower fuel.

My experience has been poor performance and smoking exhaust anytime wifey accidentally put snowblower mix into the lawnmower, My advice is do not do it.

Do NOT put gas/oil in your car, especially if it has a catalytic converter. A gallon of gas costs $3 and a cat costs $800+


Don’t worry if it’s a “small” amount. Up to a quart of two stroke oil/gas in a full tank is not a problem. It’s better then dumping it or trying to save til next year. Adding stabilizer should allow you to save it over the year. Use an air tight container to extend storage life too.

Use an air tight container to extend storage life too.

That’ll increase storage life, but it’s probably illegal and possibly unsafe because of the possibility – however remote – that pressure will rupture the container some hot Summer day. A better choice would probably be a vented container with a narrow neck that minimizes the air-fuel contact area but still allows the fuel to expand and contract.


Burning oil can coat and render inefficient and/or nonfunctional both the catalyst in the cat converter and the upstream oxygen sensor.

Your best bet is to keep it and use it in a fresh 2-cycle mix next season.

Air tight is a relative term as nothing is. I’ve seen enough collapsed tanks to appreciate the difference.“narrow neck that minimizes the air-fuel contact area but still allows the fuel to expand and contract.” is exactly what I had in mind instead of the usual open funnel. That’s exactly what I use in my 8 different storage containers. The “container must still be air tight” but vent adjustable as you imply. I don’t think we disagree.
Thanks for being more explicit in how you use it.

This reinforces my wonderment as to why people still have attached Garages and store these items in same…sheds or detached are safer.

My neighbor went so far as to place his shed storing flammables 150 yards from the nearest dwelling…lucky for everyone in the neighborhood when it “blew up” last fall in a lightening strike. Great light show !

My solution would be to purchase a late 1950’s or early 1960’s Saab with the two stroke engine so I could have some place to useup the fuel from my lawn care tools. These cars always fascinated me–I think they ruined the Saab when it went to a 4 stroke engine.

IT WON’T HURT A THING. It will provide your compression rings and valve stems with a little extra lubrication…

I had one. Other than racing or driving at speeds between 20 and 50 mph, they were a real pain with fouled plugs and pre mixing. Lots of low end torque, less power as the rpms increased. They had a habit of seizing w/o using the free wheel feature (meant new engine) which meant you never had engine braking with it engaged…that’s real “great” for long down hills. I made the mistake of buying one (it was good on ice/snow with traction from free wheel) instead of opting for the excellent v4 4 stroke for just a few hundred more…should have bought a v4 FG Sonnet. You’re lucky you did miss out on that lemon. 2 strokes gas engines are really problematic as car motors. Ice racing was the only thing I liked it for; that and letting my baseball players use it to drag the infield .
For regular use…it was the worse car I’ve ever owned, mostly due to that motor…
I should have known when I left the dealership with it, and their advice to keep it running smooth was, “always drive it like you’re going to a fire”.
Just a humble opinion from a previous owner…

I don’t see it being a problem at all. It’s already diluted down to something like 30 to 1 anyway and when added to gasoline in the tank will be diluted down much much further than that.

People have used Marvel Mystery Oil (petroleum and detergents) in both gasoline and diesel fuel systems for years and I’ve never heard of a problem with it.

Thanks for the bio.