I have seen a case for reduced friction due to changing over to M1. In 1992 I purchased a Olds Delta 88 Royal. Also the last GM junk thank god. I dumped the factory fill at 3k miles and put M1 5w-30 back in it as spec. When I started the car up after the oil change it went to a high idle. It caught its self and then went thru a 15 min. triad reseting the computer. It was really quite funny.
The only thing intresting in this cars life was. If I let the M1 go to 15k miles between oil changes. It did this reset every time. If I only went 10k miles between oil changes it wouldnt do this. There was no oil / maint. minder or any of that kinda stuff. the only thing I could figure is the additive package was depleted and it resulted in the need for the computer to reset its self. also of note the mpg went steadly down after 10k miles on a oil change.
Thats the only car Ive ever had that did that. And its strange how the mileage thing always seemed to work out.
My Ranger dosent like syn. oils at all. it will start smoking and burn them. Done this since new. But put Motorcraft 5w-20 in it and it wont use or burn a visible drop.
The Hondas are funny about there oil like the Olds was. If I run there M1 over 10k miles the valves start to rattle. Change the oil and valve noise is gone for 10k miles. Wife and I were laughing about it. In years past folks would always joke about the car needing a oil change when the valves rattled. The Hondas sure bare out that idea.
psy
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