Need advise on best rpm to cruise at

[George_Pimpdaddy]

hey just borrowed my frined mikes 1988 3/4 suburban tbi350 th400 and 14 bolt SF rear with i believe a 208. Anyways im so not use to not having overdrive as i love my 700r4, now i have to drive his truck up to meet him in the bush loaded with people for thanksgiving lol. so i thought id ask some experts on advise on the best highway rpm for cruising a 4 hour trip trying to get the best fuel mileage here too thanks guys

 

[chulisohombre]

as far as i have heard ,the sweet spot for a good running 350 to get the best milage is around 2100 to 2300 rpm.

 

[George_Pimpdaddy]

yea that sounds about right the way back i was doing like 100-110km/h at about 2100-2400 rpm

 

[badmix]

my 305 likes 2200rpm on freeway (65-68mph)

 

[dhcomp]

do you have a tach in that truck anyways?

 

[bowtiepower00]

Rule of thumb is that you want your cruise RPM to be at your engine's torque peak. If you've got plenty of torque, then typically you can run a bit lower than that without issue. The lower the RPM the better the mileage you'll see in most instances. 2000-2500 is about right for a gas V8, IMO.

I'd guess that you'll see a couple of MPG better economy at 55 compared to 65 or 75. Anything above 65 is going to drain the tank pretty quickly. If you're driving into a headwind you'll see a difference, too.

 

[dhcomp]

65-70 is about 2200 rpm's i think on my 91 350 burb with teh 4l80e.

So for turbo400, im guessing 2200 is around 55. Anythign over that, it think you are really gonna suck some gas w/o an overdrive.

 

[George_Pimpdaddy]

thanks guys im leaving in like 2 hours and yea its got a tach finally lol yea ill try to keep her around 2200-2300 have a great weekend all