"Nova" wrote in message
news:2L%sk.887$w51.156@trnddc01...

See:

http://www.smartsynthetics.com/articles/5w20oil.htm

"The main reason 5W-20 or 0W-20 oil was specified for your engine is to
increase the CAFE (Corporate Average Fuel Economy) reported to the Federal
Government. CAFE is the combined average fuel economy of all of a vehicle
manufacturers product line. Minimum CAFE levels are specified by the
Federal Government. In order for a vehicle manufacturer to continue
selling profitable large trucks and SUV's, which typically have poor fuel
mileage ratings, as compared to smaller cars, and still meet mandated CAFE
requirements, they must also sell enough of the smaller cars which have
much better fuel economy ratings to offset the poor fuel economy ratings
of the larger vehicles. For model year 2001, the change to a 5W-20 oil
will allow Honda and Ford's overall CAFE to increase by a very small
amount, typically in the tenths of a mile per gallon range. 5W-20 oil is a
lighter viscosity than a 5W-30 oil and therefore has less internal engine
frictional losses, or less drag on the crankshaft, pistons and valve
train, which in turn promotes increased fuel economy. This increased fuel
economy is virtually undetectable to the average motorist without the use
of specialized engine monitoring and testing equipment under strictly
controlled test track driving when compared to a 5W-30, 10W-30 or a 0W-30
viscosity motor oil. "


Oops, I lied; the Amsoil Signature Series is 0W30, NOT 5W30. I actually
run the Series 3000 HD Diesel in my Power Stroke which is 5W30. The F250
has in excess of 180k miles all but the first 8k on Amsoil. I put 183k
miles on a '91 Checvy 1500 Silverado 305 gas rig, all but the first 4k miles
on Amsoil and the Land Cruiser is approaching 60k. A friend has gone over
the 300k mile mark on his '96 Dodge Cummins. We both run the oil 24,000
miles between changes with filter changes at 6,000 though I've gone to 8,000
between filters since Amsoil came out with their EA line of filters (they
guarantee them 12,000 miles).

Dave in Houston