I noticed it last summer when I sneaked a tank of farm fuel in my 83 and used Howe's fuel additive. When I went back to low sulphur my mileage went back down to what it was as did the power and engine noise. I also noticed a difference in my farm tractors when I took the same farm fuel and added used filtered crankcase oil to the fuel. The tractors had more smoke but they also had more power and gallons used per acre went down. Personally I think we are getting rotten fuel. Anything from low cetane to fungus. You may have accidenaly got some primo-dino.

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1983 300-D turbo
1985 300-D turbo
1959 Harley Panhead chopper
1929 Ford coupe restored
I hang out with Boneheaddoctor at Schuman Automotive OBK#5
All liberals are mattoids but not all mattoids are liberal.