RPM sweet spot for best MPG

Turbo Performance

Turbo Performance

Member
Oct 16, 2008
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Optimal RPM for best MPG? Just did a 100+ mile round trip. 1375rpm @ 75mph netted me 30.5mpg. I'd be lying if I said I wasn't slightly disappointed and didn't hope this build would get closer to or above 40mpg on the highway. Turbos don't make any boost til 1900, so cruising was 0psi today. Am I going to do any better turning the rpm up some? Thoughts?
 
Turbo Performance

Turbo Performance

Member
Oct 16, 2008
948
12
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Idaho
plowboy_lbz said:
What gears, tires, and trans are you running?
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2.19 gear. 30x16-15 Mickey Thompson Sportsman s/r's. 4L80e trans (.75 o/d)

OregonDMAX said:
What is the weight also. What are cruising egt's?
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Weight is let's say ~<3000lbs

Edit: Missed part 2 of your question. Cruise EGT's are roughly 550-600 on flat ground. Maybe a touch less.

hondarider552 said:
1375 @ 75...?? Are you running 44's? Slowing down is the #1 beat way to get better mpg
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What? 2.19 rear gear for highway trips only. If slowing down is #1 way to net better MPG, you're insinuating aero drag is the culprit? I always figure slowing down for better mpg was due to lower cruise rpm not aero drag. I go much lower on rpm and it's idling.

My question pertains more to wondering if the engine is "happier" or more efficient in a certain rpm range and if I'm in fact in that range. Or if more rpm may actually help in my case.
 
plowboy_lbz

plowboy_lbz

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I would think that low of rpm you would be lugging the motor vs getting rpm up to 1500-1600 where the motor is closer to its peak tq.
 
OregonDMAX

OregonDMAX

NOT IN OREGON, NO DURAMAX
Apr 28, 2013
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I got best mileage above 65 and below 80 I haven't quite found the "sweet spot" but got a personal best of 24.6mpg at 6750lbs with 265's.

My cruising rpm is higher then yours by at least 200-500 rpm depending on the speed I'm at mentioned above
 
Turbo Performance

Turbo Performance

Member
Oct 16, 2008
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Idaho
plowboy_lbz said:
I would think that low of rpm you would be lugging the motor vs getting rpm up to 1500-1600 where the motor is closer to its peak tq.
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It is lugging at times, more specifically if I have the converter locked and have to slow down to 65-70 for any reason. Maybe I'll order up another set of gears to get me in that range to see if it pulls any better numbers.

OregonDMAX said:
I got best mileage above 65 and below 80 I haven't quite found the "sweet spot" but got a personal best of 24.6mpg at 6750lbs with 265's.

My cruising rpm is higher then yours by at least 200-500 rpm depending on the speed I'm at mentioned above
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So roughly 1500-1800rpm? Sounds like that may be a better spot to be in considering the peak torque rpm cruise theory. Would put me just south of any boost too.
 
plowboy_lbz

plowboy_lbz

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Why not try down shifting? Even with 4l85e I don't think it would put you above 2000 rpm. Would be alot easier than changing gears.
 
Turbo Performance

Turbo Performance

Member
Oct 16, 2008
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Idaho
plowboy_lbz said:
Why not try down shifting? Even with 4l85e I don't think it would put you above 2000 rpm. Would be alot easier than changing gears.
Click to expand...

Good point, thanks. 3rd gear 1:1 with 2.19 final would be 1850ish at 75. Might try it to see if it gets me anywhere before getting another gear set. They're only $30-$50 a set so it's not a big deal to have another set laying around.
 
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