Since the first day I have been on the board, and that is even prior to the existing BITOG, I have read that this oil or that oil turns dark and is really cleaning my engine. I never answer those posts because I have a different theory. (And my brain may have been fried years ago from the lack of oxygen while flying, so that may explain my theories and their flaws)
When I was in the Refrigeration business we took a propane torch and set it on a metal bench and welded up a metal frame so we could put aluminum pans on it. After trial and error we adjusted the height so the oil temp would reach 180 degrees. (all measured in F)We then tested refrigeration oils to see which ones coked at what temp. We could adjust the stand lower for higher temps of the oil. We were having industry problems with some compressors. We then added an additive (For Refrigeration oil) to each oil and took the readings again. None of this may be interesting, but let me give you some conclusions:
1. Some oils darkened much quicker than others at the same temp.
2. Oils coked at different temps, but we could repeat the results with each oil.
3. We added the additive, and all oils darkened much quicker. (These were eye comparisons and is subjective, but tan, brown and dark brown and black and shades in between can be differentiated)
4. Absolutely no cleaning action was taking place, it was the additives that changed color.
This may sound worthless for engine oils. So we then did this experiment with engine oils. We used Amsoil 15W40, Mobil 1 5W30, Shell Fire and Ice,(Tells you how long ago we did this), Pennzoil and Quaker State and a couple of ND oils. (They stayed the clearest at temps up to a point. Low additive package)
We achieved the same results, the oil darkened at different temps. Some quicker than others. The better the additive package the quicker it turned dark.
Then we bought a bunch a additives and added to each oil. Slick 50 included. When added to each oil, the oil would darken much quicker, whether synthetic and conventional, it just depended on the additive that we put in. Note: at that time Slick 50 was only a cheap carrier oil and powdered teflon and really did not alter the results in darkening. Some powder residue in the pan when we went to high temps.
Conclusion, judging oil in the engine by the color is worthless. I personally believe it is the additive package that is turning dark, not indicative of the oils cleaning ability. Then when you add external additives, they react with heat from the engine and cause the oil to turn dark and this is still not indicative of the cleaning ability. An additive can clean and the oil does not have to get darker.
Let me go a step further, diesel oil. This oil has a super additive package and will turn dark very easy in an engine that runs hot. But if you check the opacity, it may be black but the opacity is good which means the oil is dark not full of sludge. My 95 diesel that has had the same oil for 14 months is black, (RP 15W40), but the opacity is super, you can see the silver dipstick through it. And I had it analyzed at the 12 month interval and it has 0 soot. So what turned it dark? Well for starters it is a turbo diesel, so heat is present, and the additives turn this oil dark. I have seen some Duramax engines that the oil is still golden at 5K. So the cleaning theory of diesel oil is worthless to me. Yes it has additives that hold the soot in suspension and higher levels, normally, of additives. Therefore it can turn dark in a modern engine that runs at higher temps.
I am open to a severe battering with this post. Don't knock my testing methods, they were amateurish at best, but repeatable and open to interpretation. Three of us viewed the process.
Some will say that my cam, viewed through the oil filler, went from brown to silver using xxx oil. Yes any highly additized oil can do that if it is a soft light film. Oil has some, or better yet, extremely limited cleaning ability. The amount of cleaning additive in an oil is not even noteworthy.
When I was in the Refrigeration business we took a propane torch and set it on a metal bench and welded up a metal frame so we could put aluminum pans on it. After trial and error we adjusted the height so the oil temp would reach 180 degrees. (all measured in F)We then tested refrigeration oils to see which ones coked at what temp. We could adjust the stand lower for higher temps of the oil. We were having industry problems with some compressors. We then added an additive (For Refrigeration oil) to each oil and took the readings again. None of this may be interesting, but let me give you some conclusions:
1. Some oils darkened much quicker than others at the same temp.
2. Oils coked at different temps, but we could repeat the results with each oil.
3. We added the additive, and all oils darkened much quicker. (These were eye comparisons and is subjective, but tan, brown and dark brown and black and shades in between can be differentiated)
4. Absolutely no cleaning action was taking place, it was the additives that changed color.
This may sound worthless for engine oils. So we then did this experiment with engine oils. We used Amsoil 15W40, Mobil 1 5W30, Shell Fire and Ice,(Tells you how long ago we did this), Pennzoil and Quaker State and a couple of ND oils. (They stayed the clearest at temps up to a point. Low additive package)
We achieved the same results, the oil darkened at different temps. Some quicker than others. The better the additive package the quicker it turned dark.
Then we bought a bunch a additives and added to each oil. Slick 50 included. When added to each oil, the oil would darken much quicker, whether synthetic and conventional, it just depended on the additive that we put in. Note: at that time Slick 50 was only a cheap carrier oil and powdered teflon and really did not alter the results in darkening. Some powder residue in the pan when we went to high temps.
Conclusion, judging oil in the engine by the color is worthless. I personally believe it is the additive package that is turning dark, not indicative of the oils cleaning ability. Then when you add external additives, they react with heat from the engine and cause the oil to turn dark and this is still not indicative of the cleaning ability. An additive can clean and the oil does not have to get darker.
Let me go a step further, diesel oil. This oil has a super additive package and will turn dark very easy in an engine that runs hot. But if you check the opacity, it may be black but the opacity is good which means the oil is dark not full of sludge. My 95 diesel that has had the same oil for 14 months is black, (RP 15W40), but the opacity is super, you can see the silver dipstick through it. And I had it analyzed at the 12 month interval and it has 0 soot. So what turned it dark? Well for starters it is a turbo diesel, so heat is present, and the additives turn this oil dark. I have seen some Duramax engines that the oil is still golden at 5K. So the cleaning theory of diesel oil is worthless to me. Yes it has additives that hold the soot in suspension and higher levels, normally, of additives. Therefore it can turn dark in a modern engine that runs at higher temps.
I am open to a severe battering with this post. Don't knock my testing methods, they were amateurish at best, but repeatable and open to interpretation. Three of us viewed the process.
Some will say that my cam, viewed through the oil filler, went from brown to silver using xxx oil. Yes any highly additized oil can do that if it is a soft light film. Oil has some, or better yet, extremely limited cleaning ability. The amount of cleaning additive in an oil is not even noteworthy.
