I've been running Diesels for 35+ years. All the way from the lowly 4.108 Perkins to the 20 cylinder behemoths with twin turbos and or superchargers.
The companies I have worked for have tried just about all of the fuel additives and I can honestly say that none worked, except for the TCW3. We never did gain any MPGs.
We also tried adding additives to the oil with mixed results, several engines did not like them and we wound up in-framing them before their time. Others engines, using additives, wound up needing in-frames at the same time the manufacturer dictated.
They were also tried with regular Dino and Synthetic, every time we went back to Dino as changing oil at irregular intervals wound up being very costly. Changing a power pack, fuel contamination, water contamination.
The ONLY thing that increased time between oil changes were the addition of small centrifuges, or spinners, to the engines. We actually went 25,000 hours (on Dino - Rotella T) before oil analysis said that the manufacturers base additives were depleted. We then dumped 1/2 the oil and topped the engine off. She ran for another 25,000 hours and was overhauled.
Using regular dino oil is cost effective as the use we give the MVs does not justify the cost of synthetic.
Using fuel additives, other than the TCW3, has not proven (to me) to be cost effective or needed. Only for lubrication of the IP and injectors.
I know this will probably stir up a hornets nest, but such is life...
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