The contribution of thinner oil to CAFE requirements is Nil. I do not understand why people are wasting time arguing this relationship. This is not what increased fleet MPG. The mandate resulted in a wide range of Significant changes to all areas of automotive development. To mention a few things that added Many MPG to each car and truck includes but is not limited to (and in no order):
Streamlining vehicles top to bottom aiding in highway mileage in particular.
Fuel injection and full electronic management. This increases fuel economy while decreasing wear and tear on the engine and the oil.
Tuning both intake and exhaust systems - huge gains.
Driveline changes especially tuning transmissions with more gearing - huge gains.
Decreasing the gross vehicle weight.
Thinner oils contribution is at start up and short trips and actually aids in engine longevity. Because starting is easier, even at 90F here in Florida, there is less wear on the battery, the alternator and all internal engine parts. In fact, the engine is lighter because of the use of smaller starter motors as one example.
Even with some vehicles still weighing in at 6 or 7,000 lbs as my Ford trucks the average mileage went from 6 MPG in 1970 to 18 MPG today. This was not a function of using a 20 instead of a 30 grade oil I am certain.
In the mid-1970’s I performed an extra credit high school chemistry study of oil viscosity. I used the family cars and those of my neighbors. I think we all used 10W-30 grade. The initial thinning at around 1,000 miles would shock you. The oils were not able to hold viscosity even without fuel dilution. But with the vast amount of fuel dumped into the oil from the carburator and accelerator pumping was another league in itself. I can assure you that the 20 grade oils of today do not thin nearly as much as all the cars were running 40 years ago even though those engines were “lose”. The 40 or 50 grade oils back in the 1970's thinned just as much. This is what opened my eyes to using better, but thinner oils, that held grade.
I had the help of an oil engineer who worked for Shell at the time. We never ran the oil long enough for the real reason you had to change the oil - oxidative thickening.
I believe that those hanging onto the need to run thicker oils are scraping for statistics that simply do not exist. And a savings of one tenth of one percent gas mileage by using 20 grade oil is not going to save the plant either.
I have always strived to use the thinnest oil that did the job for me but was selective to those brands that had better technical characteristics. These numbers were available even back when I was in high school.
aehaas
Streamlining vehicles top to bottom aiding in highway mileage in particular.
Fuel injection and full electronic management. This increases fuel economy while decreasing wear and tear on the engine and the oil.
Tuning both intake and exhaust systems - huge gains.
Driveline changes especially tuning transmissions with more gearing - huge gains.
Decreasing the gross vehicle weight.
Thinner oils contribution is at start up and short trips and actually aids in engine longevity. Because starting is easier, even at 90F here in Florida, there is less wear on the battery, the alternator and all internal engine parts. In fact, the engine is lighter because of the use of smaller starter motors as one example.
Even with some vehicles still weighing in at 6 or 7,000 lbs as my Ford trucks the average mileage went from 6 MPG in 1970 to 18 MPG today. This was not a function of using a 20 instead of a 30 grade oil I am certain.
In the mid-1970’s I performed an extra credit high school chemistry study of oil viscosity. I used the family cars and those of my neighbors. I think we all used 10W-30 grade. The initial thinning at around 1,000 miles would shock you. The oils were not able to hold viscosity even without fuel dilution. But with the vast amount of fuel dumped into the oil from the carburator and accelerator pumping was another league in itself. I can assure you that the 20 grade oils of today do not thin nearly as much as all the cars were running 40 years ago even though those engines were “lose”. The 40 or 50 grade oils back in the 1970's thinned just as much. This is what opened my eyes to using better, but thinner oils, that held grade.
I had the help of an oil engineer who worked for Shell at the time. We never ran the oil long enough for the real reason you had to change the oil - oxidative thickening.
I believe that those hanging onto the need to run thicker oils are scraping for statistics that simply do not exist. And a savings of one tenth of one percent gas mileage by using 20 grade oil is not going to save the plant either.
I have always strived to use the thinnest oil that did the job for me but was selective to those brands that had better technical characteristics. These numbers were available even back when I was in high school.
aehaas
