I remember reading somewhere that tacking to little and putting a strain on the motor can net the same mpg as tacking some more. Is this true? If so what RPM is best on the highway for MPG? I find myself running 75 mph tacking 2k.

 

It depends on the vehicle and the set up, there's no set RPM that works for all trucks, there are a lot of variables that come into play...

 

IMO keeping the tach under 2k! Even from a dead stop usually nets the best mpg! Sometimes u got to go slow to get the best mpg! Ever pass that guy on the freeway who's driving to slow? He probably getting 20 r better lol

 

In my case, each time the RPMs go up on the highway, the mileage goes down

stock 4.8, 60e, 3.42s - >20mpg HWY
stock 6.0, 60e, 3.42s - >20mpg HWY (getting over 22 was not out of the ordinary)
stock 6.0, 60e, 4.10s - ~17 mpg HWY
stock 6.0, 80e, 4.10s - 16 mpg HWY
cammed 6.0, 80e, 4.10s - 15 mph HWY

So as you can see as the rpms go up, mileage went down, ranging from 1600 rpms @ 65 with the 60e and 3.42s to 2100 rpms with the 80e and 4.10s.

Best bet for anything gas mileage related is just to keep it stock.

 

Zero would be optimal.

 

To many unknowns here. What gear ratio/engine do you have? What truck, cab configuration? You need to be more specific.

Lower RPM doesn't always equate to better mileage. Take my truck for example. Big heavy 35s on 3.73s lugs the engine. It would get much better mileage with 4.56s.

 

Get a vacuum gauge and then you know what is best for your setup.

This will also help you in the WAY you drive.

 

what surprised me was a couple weeks ago when driving with a Camaro caravan doing anywhere from 85-100, i still got about 17.5 on that tank of 93 as opposed to about 18ish doing 65-70

that's in my RCSB 4x4 5.3 (93 tune) with 265/75-16s & 3.73s

 

Just as all the other guys have already said, there are just too many variables. However if you just want a basic idea, from an observation on stock trucks, most do seem to tend to get the best mileage somewhere between 1700 to 1900 on the highway. The vacuum gage idea is very telling, if you have ever tried to drive according to one, you will realize how daunting a task it can be to keep the numbers up, but it can also make you start learning how to change your driving habits.

 

Git outta my head, was my first thought when I read the title. Jay