“What is the relationship of Miles Per Gallon and batterys? - tom”
When the batteries do not hold as much charge the gas engine has to run more.
Hydbrids are dumb. A direct-injected turbo-Diesel gets 45-50mpg when you buy it and it still gets 45-50mpg 10 years later.
The “hybrid” fuel economy gains depend on the ability to store energy, i.e., in the battery. As the battery degrades, so do the hybrid benefits.
It’s a hybrid, it doesn’t use it’s gas engine until the batteries are dead or nearly so. The faster they discharge the more gas it uses as the little gas engine will run more.