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OK boyz this one is going to be a shocker. A few months ago I hinted that I switched oil to Mobil Delvac 1 ESP 5W40 and noticed a significant fuel economy shift. The problem was on the same day of this oil change I also added the Power Service Flush product not knowing I was going to see a fuel economy improvement, so wasn't sure which caused the bump in fuel economy. Well fast forward to ~ 7k miles later and on my second Delvac 1 ESP oil change and I'm fairly confident that my 0.75 - 1 mpg improvement is from the Mobil Delvac ESP oil. Historically I ran Motorcraft 10W30 and Shell T6 5W40. Want to stress this is a small test sample but the trend is impressive and I will continue to run this oil and report.
In full transparency, this oil is not on Fords approved oil list for the 6.7, but it does exceed the minimum requirement of 1k ppm for phosphorus at 1,118 ppm on this oil sample (far right column) from Speed Diagnostics from his latest video testing oil on the 3.0 Duramax.
This oil appears to be a PAO and Ester based oil per Speed.
Interesting, keep us posted. I never understood why Ford recommended running 10w30 in a diesel engine. I always make my customers run 5w40 especially if emissions are still intact and/or they tow or use their truck for work.
That is interesting. Looking forward to more updates. I recently switched to AMSoil HD (which also isn't on the Ford approved list), however, due to all that is going on, the price has went up from $109 for 4 gallons to $141. I have enough for another oil change, but after that I'll be going back to either T6 or trying the Valvoline...
Its what I have waiting for my first oil change. The only reason I can tell its not on the ford list is its sn rated and therefore usually phosphorus would be down but not on 40wt oils. An sn rated 10w30 would be too low.
All the uoa ive seen with it are great and it is mobil's top diesel oil. I'll have about 800mi on a new 25 before towing our rv through central Idaho next week. I'll change to the delvac at about 1500mi. I'm going to do oil analysis for the first time ever and I'll post the findings.
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