Outdoor Power Equipment and Small Engines - Gas/Oil Mix

I have a Briggs push mower engine that is a little older, but running okay. The oil, though, is always "burning"--it turns very dark quickly, and also mixes with some gasoline. I'm using Mobil 1 synthetic & MMO to combat any wear.

Any ideas as to how this happens? The mixing is minor but occuring nonetheless.

I have a Briggs push mower engine that is a little older, but running okay. The oil, though, is always "burning"--it turns very dark quickly, and also mixes with some gasoline. I'm using Mobil 1 synthetic & MMO to combat any wear.

Any ideas as to how this happens? The mixing is minor but occuring nonetheless.

The mixing of gas in the oil is due to the fuel inlet valve inside of the carburetor not closing all the way as it should.Not knowing what kinda carb.you have I don't know weather your carb.has a rubber seat or a rubber tip on the needle valve causing the troube.But this is the general place to look.And also if the float is metal it may have a hole in it causing it to fill will gas and weigh it down,causing the seat not to close.

Gas is in fact getting into the oil? If so, the carburetor is the problem. I don't think I would mix Marvel into the mobil1.

Thanks to you both. MMO (according to "them") is fine to mix with fully synthetic oil, no difference. At least that's what the company tells you.

So if it is this needle, does it have to be replaced?

Yes,If your carb has an inlet needle that has a rubber tip replace it.If it has a rubber seat,replace both,But like I said... if the float has a hole in it then thats going to be your trouble and you only have to replace the float.Just shake the float.You'll be able to hear the gas inside slosh around.

Okay, I'll check it out. Can you maybe explain where the oil is "going" around the carburetor? I don't know why oil is around that needle in the first place.

Wait a minute....I think that I may have misunderstoud your post.Does the oit sump have a smell of gas???

Yes! The oil smells of gas when I change it, and I think I saw some small little pockets that I thought could be some gasoline in the oil I removed. And, the oil is always black and burned looking, even after changing.

Or, to be a little more clear, the oil in the drain pan I use smells like gas. Not sure if the actual sump would or not.

we're on the same page after all........sorry.I thought that gasoline in the oil was what we we're talking about.But when ever you asked that " Can you maybe explain where the oil is "going" around the carburetor? I don't know why oil is around that needle in the first place.", that kinda knocked me for a loop.Gas in the oil is caused by the intet needle not cutting the fuel off when not needed as I was saying.Oil in the carburetor would be another story and another solution.But your problem is the fuel inlet valve not seating,causing the gas to run through the valve train and into the oil pan.

Okay, I'm going to try taking off the carburetor sometime in the next couple of days. I'm a little worried about messing something up...I just paid $50 to have the governor readjusted so it will run properly.

Where would I find a needle like that? And does it just pop in/out? Thanks again.

The same repair shop that you used B 4 will have the needle and seat that you need,Just give them the model,type & code numbers off the engine.They will be on the blower housing (recoil cover).

For a few bucks more, you should install a complete carburetor rebuild kit, not just a new inlet needle and seat. Furthermore, you should soak the carburetor in a bath cleaner and then spray if off with a evaporating type carb/choke cleaner before you install the rebuild kit. Post back with the engine ID numbers and I can provide you with the correct Briggs part number(s) you'll need to purchase.