20MPG at 60MPH in an 80? (1 Viewer)

[musthave]

I'd be curious to know how much a roof rack and arb affect mpg.

 

[PDoyle]

At least 2 mpg.

 

[Corbet]

At least 2 mpg.

I disagree. I did not notice any real change with my ARB or with my rack on or off. Tire size and lift will drop the MPG the most.

 

[greentruck]

ARB or roof rack?

Any roof rack increases frontal area, a key component in generating drag.

An ARB doesn't really change frontal area. It does disturb airflow, but this is less significant than increased frontal area in terms of MPG.

Of course, a roof rack disturbs airflow, too. A rack that sits higher above the truck's roof raises its profile, already a bad thing, but also leaves space underneath between the rack and the roof. That involves compressing the air to flow underneath the rack, as well as disturbing the airflow, so requires even more energy.

As for best RPM for mileage, I've heard between 2000 and 2100. Keeping under 2000 rpm may actually be a little to slow for greatest efficiency, but it's not something I'd worry too much about if it works for you.

I've also heard the 80's gearing was set-up to take the 33" tires typically used elsewhere in the world market to equip the 80. That's why those who switch from the stock but puny Michelins to something else in a 33 flavor often report increased MPG. It's fractional, but when you only get about 10 mpg in town, every bit helps.

 

[scrowley]

On scangauge:
long road trips on hwy I see 12.9
around town like high 10's
Usually lower 200's on a full tank to light. Mostly all backroads
1996 80, Full armor, etc, 315's, J springs
I've never done the math on paper, just scangauge

Anyone else take awhile to get good mileage when cold? Mine takes awhile for the mpg's to get descent. Looking at scangauge.

 

[kiter18]

My is 3fe 1992 i can never be better than 12mpg and i always drive slowly around 2000rpm

 

[IdahoDoug]

You guys r missing the point. It's not if your 80 can get 20mpg at YOUR version of freeway speed. He said 60 mpg. Everybody who's driven a stock 80 on level freeway for 300 straight miles with the cruise at 60 raise your hand. I thought so. Nobody. A stock original condition 80 will do it. Barely. The air resistance increases sharply on this body above 60. Trouble is nobody is patient enough and most have the check engine light an old oxygen sensors. Try it.

 

[thatcabledude]

You guys r missing the point. It's not if your 80 can get 20mpg at YOUR version of freeway speed. He said 60 mpg. Everybody who's driven a stock 80 on level freeway for 300 straight miles with the cruise at 60 raise your hand. I thought so. Nobody. A stock original condition 80 will do it. Barely. The air resistance increases sharply on this body above 60. Trouble is nobody is patient enough and most have the check engine light an old oxygen sensors. Try it.

Hand raised.

 

[Corbet]

You guys r missing the point. It's not if your 80 can get 20mpg at YOUR version of freeway speed. He said 60 mpg. Everybody who's driven a stock 80 on level freeway for 300 straight miles with the cruise at 60 raise your hand. I thought so. Nobody. A stock original condition 80 will do it. Barely. The air resistance increases sharply on this body above 60. Trouble is nobody is patient enough and most have the check engine light an old oxygen sensors. Try it.

Hand also raised, but well not on level ground. I live in Colorado. 18 is the best I could muster but did consistently.

Typed poorly from my iPhone using IH8MUD

 

[CJF]

Drove my stock 91 from WV to CA and back three summers in a row starting in 1998. Mileage always averaged out right at 18mpg. And yes, I do literally drive 60-62mph, and with the CC engaged.

Don't take that 91 out of town much anymore; now it's a 92 that gets right around 15mpg. 2.5in lift (but stock tires) on the 92; no idea if that's causing the difference.

 

[NLXTACY]

Leaving for Grand Canyon from LA tomorrow so I will be able to test my new setup. I will report back