At what rpms is the engine most gas-efficient?
In 6th gear the rpms are lowest, but maybe the engine stuggles more at a lower speed and would waste more gas than if it was in a lower gear. Whats the best rpm to stay at for best gas mileage?
Kenny

 

I think the only reason you'd want to use 5th gear instead of 6th gear is if you're at low rpms and high load (going up a long hill or something) and it starts pinging. The only other reason I could think of is if you have to give it so much throttle in 6th gear (above 50% or so) that it goes into power enrichment, but you still may be better off in 6th than in fifth.

 

I think all gas engines tend to be at their most efficient at peak torque. Someone else might be able to give better insight.

 

I think he is talking fuel efficiency......that certainly wouldn't be the case being peak torque is over 4K RPM.

My guess would be in the 60 mph range in 6th gear.

 

I agree. Somewhere between 60-70 in 6th for max fuel economy.

 

That's volumetric efficiency, not BSFC.