is it okay to pour extra unused 2 cycle fuel out into your car engine before winter ?

First, you are right not to keep petrol over the winter, it does deteriorate and tends to gum up your 2-stroke engine. But most 2-stroke oil is 5% oil, if you mix one gallon into a 20-gallon petrol tank you dilute it down to 1/4 of 1%.

My advice is just to fill your car tank right up and dilute it as much as possible.

There's another lesson here though. Don't keep a large amount of 2-stroke petrol, just get enough for a week or 2 so you have less to get rid of when the winter comes. I have a petrol strimmer and i just fill it with fresh petrol before each use, I don't keep ANY spare petrol now.

Two stroke oil is designed to be run through a combustion cycle, time was when REDEX was used as an Upper Cylinder Lubricant. In such a small amount very unlikely to have any effect at all. Remember 2 stroke mix is usually 50:1 so by the time you've put that into four gallons it'll be less than 150:1.

Recall you 2 cycle gasoline is mixed with a oil... I wouldn't do it except perhaps one gallon at a time and right away fill my tank after that to dilute it much more.... Do not be amazed in case you have smoke coming out you exhaust because the oil mix is burning. Also maintain in mind pc contro engines attempt to keep things routinely as you force and many others. And you can also now not get the response and so forth. From your engine that you are use to when oil begins burning the mixed gas

NOOOOO!!! That could permanently damage your engine, fuel tank, injection system, etc. Do not ask for car advice from a lawn mower repair shop mechanic... I would suggest taking it to a mechanic ASAP. Depending on how long ago you did this AND the ratio of how much oil you put into compared to the amount of gas in the tank. Whether this did cause damage to your car, do not do this in the future. There is no positive affect on your engine from doing this and can only cause major damage.

In response to Barnaby, 2 gallons, even in a completely full tank of gas, will most likely damage the engine permanently. I've been working on cars my whole life. I dropped out of high school and have been employed and working on cars since I was 18. I know what I am talking about.

If you already did this, keep the tank full of straight gas for a month or so. That will help dilute it further. If the "check engine" light, comes on, get it coded, but persist for a while, then get the code reset and see what happens. Modern engines have a number of (expensive) sensors.

If you have not yet done it - I would not take a lawn mower tech's advice about caring for a three thousand dollar engine, so wouldn't do it. Better to dump the stuff in an empty milk or windshield fluid gal. jug and save for haz-mat disposal.

I do. I've been doing it for 25 years.

I've been doing that to use up my chainsaw gas at the end of woodcutting season every year for 25 years, and into the same vehicle, a 1987 Toyota Pickup I bought new at the end of 1987. The vehicle is fine, it's in the driveway right now. It starts on the second try every time, never misses a beat. It's only on its second set of spark plugs.

My point, and I hope you're getting this, is that while some people will insist you're dooming your car, is that I have a fine example of just how long that doom might take to manifest. I'm not about to change my habits, and my truck runs just fine.

I wouldn't risk it clogging up the injectors is what id be worried about for a couple of litres saving the extra maintenance costs might shoot that to the shithouse, if you all ready have keep topping up the tank to dilute it as much as you can chances are it wont hurt anything, I wouldn't make a habbit of doing that.