Yes, I would THINK so, but that doesn't seem to be the case. My owner's manual says (from memory) that my car should be most fuel-efficient around 50MPH. I have no idea how that was calculated, unless whoever wrote it buttumed that the car would be in drive gear at the time. Silly me, I keep throwing it into OVERdrive and messing up their calculations. :)
On this topic, I did discover something VERY INTERESTING about my own car, and there is no way in HELL this is a coincidence:
I'd previously found that my most fuel-efficient speed was 3500RPM-43%-78MPH. At first, I jumped to the conclusion that my car was therefore designed for high-speed cruising. Then I realized HEY, that's in OVERdrive . . . I wonder what the most fuel-efficient speed is in DRIVE??? So I downshifted and adjusted the engine to 3500RPM-43%. I'll be DAMNED if the speedometer wasn't glued to . . . (you see this coming, don't you?) ********* 55MPH!!! *********
As I wrote before, there is no way in HELL that that is a coincidence. I guess my car is just a family sedan, after all. :) Designed for maximum fuel economy at 55MPH in Drive. That makes perfect sense, considering the market that the car was targeted at.
How this relates back to your question? Well most car owners (unfortunately) wouldn't use a tachometer, even if they had a good understanding of how engine performance changes at certain RPMs. (the readers of this ng are obviously the exceptions, as a greater percentage of readers of this ng probably WOULD use a tach) But, just about all car owners are familiar with the speedometer, and use it regularly. So for the manufacturer of my car to suggest 50MPH as a speed to maximize fuel economy does make sense. It SHOULD be pretty fuel-efficient at 50MPH in Drive, as that's awful darn close to 40%. The KISS principle obviously applies here. It's easiest to tell a car owner to drive 50MPH. To try to explain that they can also achieve good fuel economy at 78MPH (by upshifting) would be confusing for a lot of people. Plus, it's not good to advise people to break the law (in most areas, 78MPH would be illegal). So, 50MPH it s. -Dave
