What is more efficient when driving on the highway: slower speed with slowdowns, or faster, but more consistent speed?

If you are on a highway just move left one lane to maintain your speed when people are merging on and move back when you are finished overtaking cars. Constant speed in the 55-65 mph range is most efficient over braking/slowing and accelerating.

If your car turns 2800rpm at 60 i guess it is a small to medium (probably Jap) engine, so that speed is right in the middle of it's most efficient range. If you want to drive at 60mph you can do so in any lane, however the real issue here seems to be how you manage merging drivers. When a road will join a highway it is usually signposted to warn you well in advance. Also you will learn the locations if you drive the route regularly. Take this time to start anticipating and planning the merge - cars will be joining so start to have a good look at the cars as soon as you see them coming up/down the on ramp as well as what's in the lanes next to you. If you can find a "slot" in the joining traffic, then just adjust your speed a little to match their speed, and "zip" together with them as they join. If you see they are going too slow either speed up a little to get ahead of them before they join or change lane to allow them to merge at their slower speed. This is as much a problem with driving skill as efficiency.

Depends on your car.

My car will cruise at 60 mph at 1800 rpm, and that's about it's most efficient speed. Any slower than that and it drops out of 6th gear. Driving at 45mph and changing speeds would give significantly worse economy.

BUT, your vehicle may be different, as it seems very low geared, which will affect the fuel use at higher speed, and make your most economical speed probably a bit slower.

If you want Maximum fuel efficiency. Think for moment If you HIT the brake you use fuel to get back up to speed.

You are allowed to leave a gap you can even make it just a little larger to let others in.

Suggest you look at entire car if you really want to save fuel / Tire Inflation #1 JUNK in the Trunk cost fuel to haul stuff.

Try looking 12 seconds ahead as well as just the bumper in front of you and adjust your speed sooner for conditions. A little more gas a little less may avoid the need to touch the brake.

The more constant your speed the best .

It really makes little difference if you are going 2800 Rpm or 2810 or 2790. Take into account up hill down hill even just a little bit counts.temperature and a host of other things

The most efficient speed is a steady 55 MPH. Any faster or slower and you will use more fuel.

And if the road is 3 or more lanes in your direction, you always drive in the second lane to avoid merging traffic.

Well, depends how far you drive this way. If you're doing JUST under 60, vs JUST over 60, than the difference would most likely be hardly noticeable, however the constant faster speed would be slightly more efficient. Again, depends how far you're driving this way. There's a point at which both methods would be exactly the same consumption.

The more constant you can keep your speed, the more efficient your fuel usage.

Are you driving a truck? 3000 RPM at 60 MPH is very high and is NOT fuel efficient.

Steady speed is more efficient. Speeding back up after slowing takes a lot of fuel.

a