Synthetic Oil

[whistlepig]

Don't fall for all the hype. Cummins only "recommends" Valvaline because Ashlund pays Cummins hundreds of thousands of dollars to get there name listed. In fact the recommendation says use an oil "like". Cummins recommends using an oil with a high viscosity index and good testing characteristics. Royal Purple, Amsoil, TRC and Schaeffers all have better testing characterists than Valvaline, Mobil 1, Delo and Rotella.

I'm not saying anything bad about those last four. They are good quality oils, so noone's head should explode. I'm just saying don't make your decision based on how much money a company spends on advertising or sponsorship. Look at Pennzoil in the 80's. How many people used Pennzoil because of Mario Andretti. Pennzoil has changed their formula so it is much better today, but I bet many of you (not all) have a poor opinion of Pennzoil that was formed back then.

Cummins engines and Valvoline oils are about as serious as you can get when it comes to statistics on oils and engines. Especially when it comes to diesels. If you want to learn about oils (regardless of brand) the Cummins and Valvoline websites are the most educational that I have ever came across.

 

[bz1]

I have spent some time evaluating and testing oils for extreme use. What exactly are synthetic oils? There are two basic types I think, full synthetic and modified dino oil. In both cases the reason they work better than pure Dino oil is they have longer hydrocarbon chains. Full synthetic has a higher percentage of long chains than modified dino oil. They lubricate better because it's harder to squish long molecules out from between bearing surfaces than it is to squish short molecules. A synthetic will also lubricate better at startup since the long molecules will stay in place and stick better to metal surfaces since they are like long strings. All oils will break down. When the oil itself "breaks" down it is because the hydrocarbon chains are getting broken into shorter pieces by the heat and constant smashing. So as the molecules get shorter they squish out easily and don't lubricate as well. Both Dino oil and synthetic molecules will break down but the synthetic will take longer because it starts with a longer molecule in the first place and some synthetic molecules are engineered to hold together better. So you can't use a synthetic forever but it should last longer. As others have mentioned there are also various additives that wear out or break down. That's a whole other subject but since additives don't last forever that means synthetic should still be changed at some point. I'm not a chemist but this is my simple minded explanation of the subject. BTW, the synthetic oils that claim to make seals tighter are doing it with an additive that causes a rubber seal to swell. When swollen in this way the seals will more quickly lose plasticizer in the rubber which keeps them soft. This can backfire if the seal swells too much and begins to bind or when you change back to regular oil the seals will shrink back down and become hard and then they'll leak bad. I personally would not use any oil with an additive to swell the seals. I've testing them and it eventually causes problems. I found that if you call the manufacturer they will tell you if they have such an additive. The bottom line is that after testing many types of oil and oil additives that promise to dramatically improve lubrication none of them really made much difference other than what the synthetic molecule itself can do. My conclusion was to use a good quality full synthetic oil (the most engineered molecule) and run it as long as the manufacturer recommends. Remember that the oil and the additives can all break down. If you want to take the chance that the manufacturer is purposely being conservative to sell more oil or avoid liability then go ahead and run the oil longer than recommended . Of course there is always some conservatism involved so any oil can be run somewhat longer than recommended. The only way to know for sure if you can run it way longer is to find someone who has done comprehensive testing, or have the oil tested yourself. Why risk trashing an expensive engine over saving a couple of oil changes?

 

[jlrsn]

Anyone running Mobil 1 Turbo Diesel Truck in their tractor? It's a 5w40 made for 15w40 applications, I think. I use it in my car with good results...

I've been using Mobil 1 Turbo Diesel Truck 5w40 in my Kubota L39 for over a year. It was down to minus 27 degrees F at the beginning of this year and I have had no problems with it even in the summer which gets up to the high 70s and occasionally the low 80s. Upon start oil pressure is immediate.
Jim