Best oil additive to stop engine knock?

D

Dogred08

Joined
Oct 19, 2019
Messages
76
Location
Monroe, North Carolina, USA
I have a push mower that I got for free that smokes a little and knocks when it runs. What additive would help with both? I was considering either the grey high mileage stop or blue regular bottle stp oil additive since it's super cheap and really thick and has good reviews. Are there any other additives that might be better?

GREY STP High Mileage Oil Treatment + Stop Leak, 15 fl. oz.

http://www.walmart.com/ip/STP-High-Mileage-Oil-Treatment-Stop-Leak-15-fl-oz/19897926

BLUE STP Oil Treatment, 15 fluid ounces, 8262, Oil Additives

http://www.walmart.com/ip/STP-Oil-Treatment-15-fluid-ounces-8262-Oil-Additives/16817398
 
Have you considered just running a heavier oil in it? I had an old Cub Cadet lawn tractor that smoked and was a little noisy so I just ran 20w-50 conventional in it. It still used a little oil but ran decent.
 
I once got a lawnmower for free and it too knocked. Turned out it was the blade hitting a piece of the deck that had bent underneath. I'm sure this isn't your particular issue but, check underneath anyway. Pull the head and check that everything is moving smoothly and the spark plug is good. Then use a thicker oil instead of additives to thicken oil.
 
Use a heavier oil like 20w-50 and run it till the rod snaps in two. You might be surprised how long it will go before that happens.
 
Last edited:
Originally Posted by Dogred08
For me additives are cheaper but is heavy oil better? Btw this is a low end flat head cheap push mower nothing special.


Yeah, I understand!
smile.gif

Yes, heavier oil is cheaper especially when changing the oil. Is it better? Well, today's oils are better!

Mowers generally don't require much oil to perform well. I mean, if oil is on the dipstick at all, your usually OK! I don't think a full crank case will help with the knocking. But, please keep is posted if it does.

I'm just babbling here but:
Lots of people buy the oil and then also buy the additive too!
frown.gif

Additives generally just make your oil thicker with very little benefit(if any) in terms of their own additives/ingredient package. Typically, they just don't have much in terms of their ingredients(additives). Maybe some extra Zinc? IDK!

STP, Lucas and the like, are really nothing special but thick(er) oils made from low(er) grade oils such as Group I. Whereas, today's oils are Group II, Group II+ & Group III. Which is why most of these products are labeled as "Snake Oil"(nothing special).

With these "Snake Oil" products, all your doing is making your oil thicker when you can just buy thicker oil and spend the money once. That's all I'm saying.
wink.gif


But yes I understand. If you are just adding some oil product to the mower's engine(not changing the oil) then, STP(or whatever) maybe the the least costly way to add oil volume and thicken it up as well.

Why the engine is knocking? Who knows!

Good Luck. I love free stuff!

CB
 
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When I worked selling cars we had a manager who would check out trades and was clueless when it came to checking out an engine or transmission. He took a few gems with knocks. Service would notify him of his screw up, and the cost for the repair. There were quite a few of these gems wholesaled with a quart or more of Lucas swill in the sump.
 
I think all the thick oil additives are about the same. Buy what is cheapest per ounce. Motor Honey haz a nice ring to it.
 
I would use all blue STP treatment in the sump at this point. I'm not a thickie either since I've been running Ow20 in a car for the last 8 years.
 
You won't fix a knock with additives or thicker oil. Thicker oil or something like Lucas oil stabilizer will make it a bit quieter for a short while, but eventually you will have the same result, which is the engine knocking louder until failure.
 
Walmart was out of stock of 20w 50 so I ended up getting the grey bottle stp and the viscosity was like molasses. I added about 4oz of it to the mower and filled it with 15w40 oil I had laying around and it helped supress the knock some it's not quite a painful...‚ I also took the head off and cleaned all the carbon buildup out and put a new headgasket on it since I had one laying around and it kinda runs a little better...‚...‚
 
Originally Posted by Dogred08
Walmart was out of stock of 20w 50 so I ended up getting the grey bottle stp and the viscosity was like molasses. I added about 4oz of it to the mower and filled it with 15w40 oil I had laying around and it helped supress the knock some it's not quite a painful...‚ I also took the head off and cleaned all the carbon buildup out and put a new headgasket on it since I had one laying around and it kinda runs a little better...‚...‚

I would not have pulled the head, cleaned things up and renewed the head gasket.. Did that once and ping went the rod. I guess the rod couldn't take the improved compression.
 
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