Using STP oil treatment
- Thread starter Ken13559
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STP is usually used to thicken your oil giving you a better compression seal on your piston rings, and less blow by. Your combustion chamber will also burn with a little more power. If you have alot of hours on your engine, it maybe that the engine is getting weaker with use (as in normal wearing out). A new engine on an engine dyno has actually shown to lose power from thick oil. Do you know what the RPMs were when the engine was newer? I've seen alot being a mechanic for 40 years. Anyways, if your not burning the oil, an increase in RPM is a GOOD thing.
2GM20F is 10 years old with about 1400hrs. I can get to 3600+rpm with stock 2blade 15"Dx10"P (1st few years from new). 3blade CSP 14"Dx6"P max is 3650rpm, CSP 14"Dx7"P max 3200rpm. With 2blade 15"Dx12"P Flex-O-Fold max is 3200rpm. Finally with KiwiProp 16"Dx18deg max before STP is 3200rpm, and after STP is 3500rpm.
Engine is burning alittle oil (not alarming) before STP. I know 2 years back, I had ran the engine for >40hrs on a passage and later on routine maintenance, discover the oil level to be right at the bottom tip of the dip stick. The oil pressure didn't come on at all during the 40hr passage. Perhaps I've wore the rings somehwat?
Should I have the engine overhaul and changed the rings or just stick with STP?
Engine is burning alittle oil (not alarming) before STP. I know 2 years back, I had ran the engine for >40hrs on a passage and later on routine maintenance, discover the oil level to be right at the bottom tip of the dip stick. The oil pressure didn't come on at all during the 40hr passage. Perhaps I've wore the rings somehwat?
Should I have the engine overhaul and changed the rings or just stick with STP?
I remember...
I remember when my dad used STP in the 70's. He checked the oil level once a week, because that's the way he did things. He noticed that the oil got real dark, real fast so he changed the oil. The oil filter was completely filled with STP and the filter was being bypassed. He stopped using it!
Years ago an oil manufacturers rep told me, "If you are adding something to your oil to achieve a desired result, you are using the wrong oil".
Additives of any kind is a band-aid, that the end result is an overhaul. And typically relatively soon.
Additives of any kind is a band-aid, that the end result is an overhaul. And typically relatively soon.
I have used 20w50 for years in my farm equipment diesels, That is a little thicker than what you are using and could be your answer. I would not go from the 15w40 to a straight 40w. The STP additive probably increased your compression and that is extra horsepower. STP has been around for a very long time and will not hurt your engine in any way. It also has additives that reduce friction, also a good thing.
As for doing anything such as rebuilding your motor just say "NO". 1400 hours are not enough reason for anything to be done. If there was a measured loss of compression in any cylinder then you start looking for the reason. The same for serious oil consumption. A good fuel additive that will clean and lub the valves and injectors is a good idea.
Enjoy your sweeter running iron genny and sail forth.
Ray
As for doing anything such as rebuilding your motor just say "NO". 1400 hours are not enough reason for anything to be done. If there was a measured loss of compression in any cylinder then you start looking for the reason. The same for serious oil consumption. A good fuel additive that will clean and lub the valves and injectors is a good idea.
Enjoy your sweeter running iron genny and sail forth.
Ray
the engine is 10 yrs old, you have been using the same brand/type of oil in it for 10 years without incident.... so what is it that makes you want to experiment with different engine oils or additives? are you looking for smoke, or loss of compression?.... maybe a miracle oil that will decrease your fuel consumption? well, 2 out of 3 ain't bad....
thicker oil isnt the answer for the engine you describe. it will move slower thru the engine and carry away less heat..... it will also hold its heat longer than a thinner oil. a thicker oil will cause significantly higher fuel consumption... and less power delivered to the flywheel. a thicker oil will add nothing positive to the mechanical operation of your marine engine...
a lot of people use a lot of different kinds of oil in their engines, and most of them meet or exceed the lubrication specs that the engine manufactures call for.
and there are some unnecessary additives that can be added to make the engine run a bit free'er (PTFE) than oil alone will, but they are usually a waste of money for any real long term effects or savings..... unless the additives damage the engine, then the effects will last awhile, or at least until your savings are spent repairing the engine.
Thicker "higher viscosity" oils, are generally only used at higher temps. 20W50 for example, shouldn't be used below 32F, and really shouldn't be used below 40F. And 5W20 really shouldn't be used above 40F, though in this day and age of economy some manufactures disagree.
It is difficult to say what the STP did. A compression test, particularly on a freshly shut off HOT engine, would be beneficial. Then, a change of oil back to the stuff you were running before the STP, a few hours running, noting if RPM's drop back, followed by another compression test, may hold a lot of information.
At operating temperature, once the oils pushing 180F, STP wont have much effect on overall viscosity, so I cant buy into the greater ring sealing theory. Especially as its about 400F up in the rings, where even STP is like water.
But STP is an additive and it does have detergent capabilities. Perhaps it washed something out of the governor that had been gumming it up.
Or it could be entirely coincidental. Do you have a knot meter? Does it show any change with that 300 RPM jump?
The correct prop should allow the engine to reach full RPM. 3600 in the case of this engine. Choosing a prop that holds it back to 3200 is hard on the engine, and will shorten its life, but that's likely unrelated. Perhaps it never was making full power, and now it is. Or, perhaps something went wonky in the injection pump and its putting in more fuel, making more power than its rated at. In that case you would want to throttle it back to 3200, as the extra could shorten its life rather quickly. Or, perhaps just as coincidentally, something hit the prop and damaged it so its slipping more, giving you more RPM rather than thrust.
In any event, I would give it a thorough investigation. 300 RPM is quite a jump to see on an engine that's had a steady history. And im just guessing its not the STP, but either something its de-gummed, or something totally coincidental.
It is difficult to say what the STP did. A compression test, particularly on a freshly shut off HOT engine, would be beneficial. Then, a change of oil back to the stuff you were running before the STP, a few hours running, noting if RPM's drop back, followed by another compression test, may hold a lot of information.
At operating temperature, once the oils pushing 180F, STP wont have much effect on overall viscosity, so I cant buy into the greater ring sealing theory. Especially as its about 400F up in the rings, where even STP is like water.
But STP is an additive and it does have detergent capabilities. Perhaps it washed something out of the governor that had been gumming it up.
Or it could be entirely coincidental. Do you have a knot meter? Does it show any change with that 300 RPM jump?
The correct prop should allow the engine to reach full RPM. 3600 in the case of this engine. Choosing a prop that holds it back to 3200 is hard on the engine, and will shorten its life, but that's likely unrelated. Perhaps it never was making full power, and now it is. Or, perhaps something went wonky in the injection pump and its putting in more fuel, making more power than its rated at. In that case you would want to throttle it back to 3200, as the extra could shorten its life rather quickly. Or, perhaps just as coincidentally, something hit the prop and damaged it so its slipping more, giving you more RPM rather than thrust.
In any event, I would give it a thorough investigation. 300 RPM is quite a jump to see on an engine that's had a steady history. And im just guessing its not the STP, but either something its de-gummed, or something totally coincidental.
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