Fuel consumption vs. RPM

[ScottI2R]

Hi all,
Is it posible that an engine would get better fuel economy at a higher rpm as opposed to lower?

My question, although it seems simpleton, is based upon my 95 eclipse. 85% highway driving for work. This vehicle appears to obtain better fuel economy in the 75-80mph range than the 60-65 mph range. Rpm's are 2700-3000 vs 2100-2400. It is an auto trans, non turbo, non all wheel drive. 2.0l.
It seems that aerodrag alone would hinder better mileage.

I personally like operation @ 80 as opposed to 60. 60 seems to take forever to get to work.

Thanks for any considerations of this question,

Scott

In a hundred years, it isn't going to matter anyway.

 

[Tmoose]

"On a side note: I'd be curious why there are very few cars that do actually have a very high (economy) gear? "

My 1975 Volvo 4 (no OD) speed travelled about 17 mph/1000 rpm

Various RWD Volvos of the 80s were geared for about 27 mph/1000 rpm in "high" gear.

My wifes 2006 Mazda MPV is more like 30 mph/1000 rpm.

I rented a Pontiac GPX or Z or something. OD lock high gear was over 30 mph/1000 rpm.

 

[izzmus]

Dead thread, but the type of fuel induction also plays a role.

I've found that spinning a carbureted Wankel (Mazda 12A rotary) in a lower gear nets better fuel economy than lugging it in top gear, since spinning the engine keeps the carburetor out of power enrichment mode due to higher manifold vacuum. The difference here being ~5500rpm at 80mph instead of merely 4000. I could return 30+mpg this way.

It's also interesting to note that the early cars had a choice of a 4 speed or a 5 speed, which had identical gear ratios plus an overdrive. They returned the same fuel economy in practice, but people preferred the 5 speed for the lower cruise RPM.

With "smarter" fuel injection, it's no contest - lug the engine and open the throttle up.