I keep seeing post after post about fuel economy. It's understandable as gas prices rise. How ever, much of the concern is really unwarranted and discussion unproductive. I'm an engineer and my specialty is cars.

If you have a mod that improved your fuel economy an amount you measured, post it in this thread and maybe we can get them all in one place.

Our 4x4's have two things that make them good 4x4's and fuel inefficient at the same time. One, they have terrible aerodynamics due to ground clearance. Lots of air gets under the truck where there isn't a smooth surface to be found. Two, they are heavy. Their strong frames which make them so durable off road weigh a lot. 4000lb is a lot of truck to move. It takes energy to move mass period. That mass will hurt the city fuel economy. Yes, there are other interactions between the auto Vs. stick, pickup Vs. 4runner, 2wd Vs 4wd, etc... but these two qualities mean you just aren't going to get very good mileage out of them and it gets worse fast when you add off road goodies.

For comparison, I until recently had the pleasure of owning and driving a 1994 Ford Explorer Limited and my 1994 Toyota 4runner SR5. The Explorer was a 2wd low to the ground SUV with a 4.0L V6. My 4runner is a 4 wheel drive SUV with a mild lift, a lot more ground clearance, and a 3.0L V6. The 4runner also weights a bit more. Each vehicle ran flawlessly and got about the same fuel economy. Yes you read it right, the 3.0 in the more aerodynamically obtuse and massive vehicle got fuel economy on par with the larger engine in the more fuel efficient chassis.

If I had that 4.0L in my 4runner, I might very well see a drop from where I am now. The 3.0 is therefore not an inefficient engine compared to its contemporaries. Please STOP blaming the engine and realize it's the TRUCK AS A WHOLE that is inefficient.

If you want to improve your MPG, there are things you should do.

Driving habits: The more you press the pedal, the more fuel you use.
Automatics: When on the freeway, press the button to shift it to 3rd instead of flooring it. This will cause the torque converter to lock in 3rd as opposed to flooring it which won't. This will also keep the tranny cooler.
Keep the engine in good tune.
Advance the timing. There's a good thread here about it and I'm going to do it soon.
Don't run over geared. (keep tire size down or regear)
Get an extra set of tires for the street that are exactly the right size and have the most mild, smoothest tread design you can find.
Free up the exhaust. I did that after my cat was stolen with a higher end custom cat-back system and got about 1.25mpg better along with a freer revving engine.
Intake mods? I can't say from experience but I would couple them with exhaust mods. You need to get air in and out. Using any new found performance gains via heavier right foot application will negate any efficiency gains from better breathing mods.
Reroute the crossover pipe. I intend to do this soon and will quantify the mpg increase thereafter. Maybe someone who has done this will speak up. At the very least is should cool down cylinder's 5 & 6 where the HG's blow a lot.
Electric fan? Certainly in some cases like when the engine is cold and the mech fan is engaged that would help. I'm sure that's a bit more of a climate dependent improvement. I read mixed reviews on this so read up and make your own decision.
Keep tires aired just a tad on the hard side. You don't want to wear them out quickly but harder tires have less rolling resistance.

If are getting mpg in the mid to high teens in an auto 4runner 3.0, you are doing well. Any higher and you are an mpg elite.

Sure there are drastic changes that can help. Going to the newer 3.4 with OBDII control systems Vs. the 3.0's OBDI, better breathing and ability to maintain vehicle performance at lower RPM's can help. A diesel swap would be even better. But those are not typically money saving moves, they are power improvement moves or moves done when the cost is negated by the fact that the stock engine needs sufficient work to be functional again.

So, unless you find a really novel way to improve the mpg of the 3.0 and want to share, or can say such and such a mod made such and such a difference, how about we just move on from the mpg threads because most of us are getting exactly what we should be.

If you have a mod that made a difference, post it here and we'll get them all in one place

Frank

Here is my truck's mods and fuel economy.

K&N drop in
cat-back exhaust system
auto tranny
31's AT's
1.5" lift
4.88's
CEL is on due to code 71
CA winter fuel formulation (typically 8-10% reduction in economy over summer)
No AC usage, temps cool enough to keep the fan clutch from engaging often
100% highway, 70-85MPH - 17.3 mpg (went to LA yesterday and got back this morning. Went 283.7 miles on 16.4 gallons)
100% city, as low as 13.5 mpg
My driving mix, I get usually get around 15-16 mpg.

 

Amen.

Now make every noob read this.

 

What is you opinion on a cold air intake such as the K&N or the Airaid? Do these add ons realy improve the MPG's?

 

Honestly, I don't know how those systems affect mpg from personal experience. I have a K&N drop in because I like to wash it after wheeling trips. It's paid for itself already a few times.

The current air box pulls in air from the fender well which should be colder (ambient) than in the engine bay. At low loads/RPMs, the restrictions in the intake don't affect flow much. Freeing up the intake (and exhaust) will help to produce more power since the engine can rev higher more easily. (power = torque X rpm) However, revving high uses more fuel.

I suppose these mods could help with power and at least not hurt mpg if the vehicle is driven gently.

This is where I hope people who have these systems will speak up.

BTW, any mod that puts an air filter exposed under the hood is probably pulling in warmer air than the stock box, just more of it.

Frank

 

Hey Frank:

We get the 18mpg that www.fueleconomy.gov says is the best we can get out of a 94 4x4 4Runner /5spd. No complaints here.

Just replaced the headgaskets. From what I can see the muffler and cat are the originals. with all the huge haeavy clouds of white smoke coming out when the gaskets were blown, I would doubt we have any exhaust restictions but we want to replace that suff asap with a free flow cat and new muffler. Stock fit would be nice because the pipes are structurally fine.
Just wanting to reduce back pressure and exhaust heat build up I would guess. Still looking for a simple cost effective replacement for those 2 parts.
Any suggestions.

 

I've started worrying a little more about MPGs since gas prices could be heading up another dollar but I know my 4Runner simply won't see over 18 in the city and that's the reality so this fall I'll be buying a late '90s Civic for daily driving duties and keeping the miles off of my Runner and won't care about the 16-18mpg my Runner gets.

 

thats a really good way of putting it.

 

THANK YOU!!!! This post is LOOONNNGG overdue

Complete waste of money. Put it on if it makes you feel cool. It won't do anything for power or MPG.

 

In addition,

QUIT WHINING ABOUT POWER AND FUEL ECONOMY. You can't have both.

 

Good post, but in the list of things to improve fuel economy you missed the most important, driving habits. When I watch the way some people drive I'm not surprised they're getting low mileage. Accelerating towards a light that just changed to red, hard aceleration when it's not needed, etc. Most people could improve their mileage 10-20% by just driving more smoothly and looking further ahead than the front of their own hood.

 

Amen Brotha...

I feel like a grandma sometimes but when I take it easy on the skiney pedal I can easily go another 50+ miles per tank. Thats like 2 mpg better.

 

Good point!

I'll amend my post.

Frank

 

I have to believe that driving habits make the biggest difference in MPG. Its a game to me. I see how long I can coast down hills and up to lights and I try not to shift above 2500 rpms. I take much more pride in calculating my 18-20 mpg at every fill-up then I do passing someone on the highway.

Andy

 

Another good one is try to keep your truck moving at a stop light. Or time them right so you don't come to a complete stop. You use the most fuel just getting the truck moving from a dead stop

I noticed a little extra mpg after I blocked off my EGR valve.

Hey guys, is there a drop in amsoil nanofibre filter for our stock airboxes?

 

i couldn't agree more, it is near impossible to have both power and good fuel economy.
with my 3.0L V6 petrol 5 speed manual i get:
Highway: 21MPG
City: 17MPG

My 3.0L V6:
K&N drop in
no Cat. Converter or Muffler (soon to have Downey Ceramic Headers)
very well maintained engine that runs like new
265x75x16R Toyo Open Country M/T
Lund Moon Visor
Lund side Window visors
No Running Boards
No Bug Deflector


things i'm getting:
Toyota rear Spoiler w/ integrated 3rd brake light
custom front bumper
full underbody skid plates (as seen on the 2006 Land Rover LR3 HSE)