We have a small Kubota diesel tractor. Its amazing how long it will run on a gallon of fuel. It only holds about 8 1/2 gallons and I only have to fill the tank once or twice a year. Yes you read that right, once or twice a year is all. We use that tractor quite a bit. What I don't understand is that if Kubota can achieve such good fuel mileage, why can't others? Our tractor is only 32 horsepower and I know that is too small to pull a car, but it seems to me that an engine with 2 or 3 times that much power would pull a small car nicely. So take that to the next level and say that it uses 2 or 3 times as much fuel as our tractor engine. Thats still really good fuel mileage. I remember reading many years ago that some college students put a Kubota tractor engine in a small car and it got well over 100 miles per gallon.
So why do the cars we drive now get such terrible mileage? We do expect too much in size, power, and comforts. I'm sure that has an affect on mileage, but is there another reason? I really don't know. Cars now get slightly better mileage than comparable sized cars of 30 years ago, but with all of our technology I don't think the improvement is enough. The way our modern day cars get better mileage is by using computer controlled everything, along with many expensive valves, solenoids, sensors, etc. Kubota on the other hand is still building relatively simple straight forward diesel engines with cast iron blocks and heavy parts.
I think our automobile manufacturers need to take some lessons from Kubota, and maybe some of the other diesel engine manufacturers as well. Maybe there are others that are as efficient as Kubota, but as far as I know Kubota is tops in fuel savings. We are spending billions of dollars researching and experimenting with this and that, trying to find a better way to conserve fuel, or make cars run on a different kind of fuel, and all the while, Kubota is calmly doing what they have been doing for many years; making tractors that run forever on a gallon of diesel..