I have used M1 0/40 in my Navigator for the past 10k miles. The 60k miles before that were all run on the spec 5/20. Never had any problems with 5/20. UOA's showed that even my severe duty driving did nothing to cut down the 5/20 or increase wear metals.
Recently, I decided to drop in the 0/40 to quiet the 1250rpm light load cam phaser rattle and because I have plenty of it, being the owner of 2 German cars.
Over the past 10k miles, I have been able to find exactly no evidence that my fuel economy has been impacted in any way at all. Whether it be hand calculations, instant MPG monitor, or average MPG monitor, everything shows I am getting better fuel economy.
The real evidence came this past month on a trip to Tampa. Every single time I go there, I use 3/4 of a tank, driving at 80mph. The past two times I have gone, I have driven at 90mph and didn't even use 3/4 tank getting there. Filling up before I left both times verified that there is no inaccuracy in my gauge. In both instances, I had more than 8 gallons remaining in my tank, where usually there would be less than 7 gallons remaining. Hand calculations of my fuel usage per mile also show slightly better fuel economy now than my driving on 5/20.
Is the phaser rattle gone? Absolutely. Did my fuel economy suffer? No. Do I feel there is a deficiency in 5/20? Also no.
But my engine is definitely not suffering any horror from running a thicker oil.
My UOA will be in soon. Greatly anticipating those results.
Recently, I decided to drop in the 0/40 to quiet the 1250rpm light load cam phaser rattle and because I have plenty of it, being the owner of 2 German cars.
Over the past 10k miles, I have been able to find exactly no evidence that my fuel economy has been impacted in any way at all. Whether it be hand calculations, instant MPG monitor, or average MPG monitor, everything shows I am getting better fuel economy.
The real evidence came this past month on a trip to Tampa. Every single time I go there, I use 3/4 of a tank, driving at 80mph. The past two times I have gone, I have driven at 90mph and didn't even use 3/4 tank getting there. Filling up before I left both times verified that there is no inaccuracy in my gauge. In both instances, I had more than 8 gallons remaining in my tank, where usually there would be less than 7 gallons remaining. Hand calculations of my fuel usage per mile also show slightly better fuel economy now than my driving on 5/20.
Is the phaser rattle gone? Absolutely. Did my fuel economy suffer? No. Do I feel there is a deficiency in 5/20? Also no.
But my engine is definitely not suffering any horror from running a thicker oil.
My UOA will be in soon. Greatly anticipating those results.