Is 10W-40 the Geritol for old engines?

Back in the 1970s, I used 10W-40 in my Ford Maverick. When I traded the 1971 Maverick for a new Oldsmobile Cutlass with a 260 V8 engine, the owner’s manual specified either 10W-30 or 10W-40 oil. I chose 10W-40 thinking that thicker was better. However, I had a problem with carbon build-up and about every two months I would have to add a can of Casite Motor Tune-up to the gas tank and then take the car out in the highway and blow out the carbon.
I then heard on a Cartalk radio program that the polymers in 10W-40 could cause carbon build-up on the piston tops. I switched to 10W-30 and had no more problems with carbon build-up. For that reason, I stayed away from 10W-40 oil.
I have a lawnmower that I bought in 1992. The manual calls for straight 30 weight oil. About three years ago, it was burning oil so badly that I was fogging for mosquitoes while I mowed. For an experiment, I bought a quart of 10W-30 full synthetic oil at the local farm store for $2.79. The oil consumption was reduced 75% until the end of last year. I stopped the mower engine and I couldn’t restart it. I put the mower away for the winter. I was going to junk the mower, but when I got it out this spring, it started right up even with the old stale gasoline in the tank…
I decided to go ahead and get the mower ready for spring. I went to the farm store and bought a quart of 10W-40 conventional oil on sale for $1.99. I changed the oil in the mower, sharpened the blade and cleaned the air filter.i have mowed my yard 6 times and the mower hasn’t used any oil and runs really well. If the mower dies, it doesn’t owe me anything. My opinion of 10W-40 oil has changed. I am just hoping the bottle of Geritol that a friend gave me will do for me with my geezeritis what the 10W-40 did for my mower engine.


I have to wonder if a coked up ring was solved by synthetic, Guess I would say keep using synthetic.

@Barkydog You may be right, although the engine went back to burning oil when I was using the 10W-30. When the engine wouldn’t restart after I stopped to take a break, I took out the spark plug, pulled the starter cord and put my thumb over the spark plug hole. The engine didn’t seem to have much compression and before I stopped to take a break the engine didn’t seem to have much power. My only explanation is that somehow the synthetic oil may have freed the stuck rings while the motor sat over the winter. I suppose there may have been enough raw gasoline in the cylinder to free up the rings
The only reason I bought the 10W-40 was that it was the cheapest oil on the shelf. I figured it would buy me time to shop for a new mower. I didn’t want to spend much on the mower. a Homelite-Jacobsen, because parts, including a replacement blade, are no longer available. The handle broke and a new handle isn’t available. I repaired the handle with a piece of electrical conduit. The mower has two blades on the motor shaft and is strictly a mulching mower. It does such a good job so I have tried hard to keep it in service, but it isn’t worth spending a lot of money on keeping it going. The 10W-40 may have not been what made it run better without burning oil.
I am not sure that Geritol will free my stuck rings and give me more energy. I may have to go to a self propelled mower, much as I hate the complexity of the system that drives the wheels.

Yes I hear you, my 89 snowblower, would run then after 20 minutes, maybe less die and not restart. 10 years ago it was debris filling up a pencil eraser size filter building up in the bottom of the tank. cleaned it out all is good. New this last winter, Repair place said probably this ignition thing failing, very expensive to replace and probably not worth it. New snowblower in the fall for me.