MPG improvement (1 Viewer)

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nissanh

nissanh

Joined
Sep 9, 2016
Threads
70
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2,890
Location
Odessa/Midland TX
When I bought the truck with 220K miles with no maintenance history, I received
barely 9 MPG in the city and 12.5-13 MPG highway

In the past few months I did the followings:
1) Denso Platinum TT plugs
2) Replaced four Chinese coil packs with OEM
3) New OEM fuel filter
4) Ran three cans of Gumout Multi-system cleanup (just saw Advance is selling it for $4.50)
5) Turned off OD in the city when the speed limit is 40 MPH or below

I did a fill up today and the followings are the readings. I fill all the way to the cap, wait and refill.
Miles driven: 221.4 (all without AC)
Gallons (regular): 20.18

City MPG: 10.96

Also, did highway at 79 MPH with AC on for 252 miles. It took about 17.5 gallons! MPG 14.4.

The only reason I am doing the MPG calculations is to make sure the truck is running at its maximum efficiency.

Brake pads OEM, fresh gear oil in all 3 diffs, drive shaft lubed, OEM air filter, 265 75 16 10 ply tires with 29 PSI in front and 32 PSI in the rear, fresh brake fluid and P/S fluid.
 
We didn't buy these trucks for the MPG, don't think about it too much or you won't enjoy driving it.

Since i put 33's on i've been getting 11mpg or so, lifting it didn't help either...i still rather take it to work than my 95 camry beater that gets 35mpg some how, way above the EPA rating.
 
Still sounds a little low to me. I think my mom's '98 gets 16mpg on the highway, and it's lifted and got big tires and whatnot and has 230k on it.

Do you have an OBD-II reader? You can take a look at fuel trims, O2 sensor voltages and stuff and see if there's something fishy going on.
 
I agree that sounds low. I just got my 9th LC/LX since 1996 and family still drives six of them. I have checked my miles and fuel many a time over the last 21.5 years and can’t remember ever getting less than 11.5ish mpg. The newest addition ‘99 LC with 312k and 285s with 45 psi just gave me 13.9 mpg around town. But it will probably average 13-13.5.

It is very typical for me to get 12.5ish in my 80s around town and 1-1.5 extra on Hwy. 100s get about 13.5 around town. Most of all calculations are with very high miles and oversized tires. I am not OCD about redundant money wasting overrated maintenance. Couple of things I do that may or may not help is keep a oil catch can on the three 80s and add B12 to gas in all of them from time to time. The End.
 
Without going into a long dissertation ... but relaying my recent direct experience with fuel mileage of late.

Include the FPR (Fuel Pressure Regulator) in your 90k PM routine or certainly at the 2nd 90k PM.
Include hot & cold testing, cleaning and mapping of the injectors at 90kPM or very least 2nd PM.
And this is YUGE: Do NOT fill the crankcase more than 1/2 way between Low and Full on the dipstick. Be sure to check this with the truck leveled!

Now getting 13.5mpg, even with mountain pass climbs thrown in the mix, in full tour mode (~8,000lbs) ... up from 9-10mpg recently before above work. My Columbus RTT and rack account for about 1mpg and the 10000CST silicone stuffed fan clutch account for another 1mpg. So, relatively speaking of course, I'm ecstatic with 13.5mpg (and running Cooper 305/75R18 tires which are known for sucking up another .5 or so mpg).
 
Kudos to you @nissanh for tuning for the best MPG.

I agree MPG is a great indicator of health of our rigs.

Some of the factors that play a roll in MPG:
  • Flat, hilly and traffic of/on roads plays it's roll.
  • Idle time.
  • Gasoline grade and qualilty.
  • MPG in the mile high city is high/better than those driving at sea level.
  • RPM (speed) one drives at.
  • Driving style is a big factor. Those with lead foot off the line will kill the MPG.
  • Certainly tire size will play a "roll", not only affect odometer readout but increase or decrease in drag.
  • Weigh add on's or reductions, like third row seat, iron bumper(s), passengers, cargo, etc all have their effect.
  • Air conditioning use.
  • The use of the interior cabin fan(s) will take about .5 from MPG. In fact use of any electrical device will draw current working alternator harder dropping MPG.
  • Here is one a member just made me aware that I'd never consider; "oil level". It seem he'd been searching for a long time why he was get MPG below 10 MPG. He did a number of things to tune with only minor improvement. Then one day he noticed his oil was over the full line. Once he brought level down his MPG jumped up (about 30% IIRC). His rig s is a heavy being build but sill wasn't near what other build rigs are getting, until he drop oil level to normal.
  • Oil's, lube's and grease's viscosity in engine, transmission, gear boxes and bearings.
Looking more at engine; being well tune with zero vacuum leaks is very important. One issue we can't do much about:

  • Compression will drop a bit with age, very little other than history of good oil and fuel can be done about this.

There is three things I was looking at on my 14 year study of MPG with The King (my 01 LC I just sold), that I'll not know effect now that I no longer have it to run test.
  1. Valves: Gap adjustment, seat and/or guide condition. Very little data on our valves being in or out of spec with mileage. Lack of data has a lot to due with not having issues in this area.
  2. Fuel pressure regulator. This is something I only just this year became aware of, we may all have issue with. It seem a clue is vary MPG with temperature. Condition itself not enough to set off CEL. RPM changing at stops different times, when all but outside temperature condition are constant may be 2nd clue.
  3. Fuel injector issues not bad enough to set off CEL. Excessive fuel smell may be one clue here hard start another, but neither indicate weak spray pattern.

Some threads I've been involved in on the subject:
Who’s got this best mpg?
MPG, how to improve?
Drop in altitude Drop in MPG??
When to replace fuel injectors
 
nissanh said:
I fill all the way to the cap, wait and refill.
Click to expand...

You can tank up that way if you like, but chances are you are pushing liquid fuel into your charcoal canister, which is designed to only handle fuel vapors. This will kill the charcoal can.

Kind of a "hot" topic lately: 100 Caught fire
 
PabloCruise said:
You can tank up that way if you like, but chances are you are pushing liquid fuel into your charcoal canister, which is designed to only handle fuel vapors. This will kill the charcoal can.

Kind of a "hot" topic lately: 100 Caught fire
Click to expand...
Good point and True on the 03-07 which have charcoal canister in rear above spare tire. Toyota 03-07 OM states: stop filling at first auto shut off of gasoline pump.

Not and issue with the 98-02, which has CC up front in engine bay. I topped my 01 with triple squeeze of pump handle every fill up for 14 year, even at high altitude then driving even higher.
 
ive been getting around 13.3 mpg with 285s, a lift, and bumper not too shabby
 
using cruise control is very helpful. I even us it on known dirt roads just to extend range (you never know if the road you want to exit from the desert is closed and you'll have to turn around)
 
Kofoed said:
using cruise control is very helpful. I even us it on known dirt roads just to extend range (you never know if the road you want to exit from the desert is closed and you'll have to turn around)
Click to expand...

The negative performance and fuel sucking issue I have with the cruise control on my '99: It will hold the lower gear's higher RPM well beyond the crest of a given climb.
 
last week I drove to tampa across I10 and I75, 490 miles one way. My truck was downshifting on all those little uphills when I got further into Florida. I thought that was weird so I tested mileage. (and changed air filters when I got home) But I got 15.33 calculated and corrected for 275/75/18 with probably 200 pounds of work gear. 45/50 psi respectively. 70-72mph corrected. Air filter was only 10 months old.
I got 16 something before the new tires, that was 15k miles ago.
 
2001LC said:
Good point and True on the 03-07 which have charcoal canister in rear above spare tire. Toyota 03-07 OM states: stop filling at first auto shut off of gasoline pump.

Not and issue with the 98-02, which has CC up front in engine bay. I topped my 01 with triple squeeze of pump handle every fill up for 14 year, even at high altitude then driving even higher.
Click to expand...

I know of folks with other vehicles with the can up in the engine bay who have had issues after years of topping off the tank. Weird, hard to diagnose issues that went away with a fresh charcoal can.

I just stop at the first click. I have enough other bull$h!t things to fix w/o adding charcoal cans to the mix...
 
Kofoed said:
using cruise control is very helpful. I even us it on known dirt roads just to extend range (you never know if the road you want to exit from the desert is closed and you'll have to turn around)
Click to expand...

I always have thought (with no evidence) that cruise control kills my mpg. I always turn it off and drive conservatively when I’m worried about range on a tank. My cruise control makes no use of momentum. It’ll cut speed near the bottom of a hill when I need to build up momentum to coast up the other side or it’ll downshift hard to maintain speed over a crest even though I’m close enough to maintain right over it.
 
FWIW my charcoal canister was shot when I bought my truck at 137k. 2006 LX canister above spare tire. No idea how P.O. topped off his tank. This part is unreasonably expensive to replace.
 
Replies:
You’re not gonna be in the good mpg range at 79 mph. :
YES I DID HIT 79 MPH CRUISE FROM AMARILLO TO ODESSA. Speed verified with GPS and odometer. I filled gas to the cap from Amarillo and drove 252 miles through Lubbock. When I reached home I noticed the gas gauge was sitting above 1/4. I really was stunned to see 252 miles and gauge is not 1/4!

All my toyota's have the charcoal canister in the engine bay which is above the gas tank so yes, I fill to the top on all 3 vehicles and no problem so far.

I will fill the engine oil level half mark next time. Something easy and saves $$$ and environment with waste oil.
 
I have 2 cruisers so im aware of their fuel mileage and yes 14.4 at 79 mph is about right for a factory tired rig.
 
spressomon said:
Without going into a long dissertation ... but relaying my recent direct experience with fuel mileage of late.

Include the FPR (Fuel Pressure Regulator) in your 90k PM routine or certainly at the 2nd 90k PM.
Include hot & cold testing, cleaning and mapping of the injectors at 90kPM or very least 2nd PM.
And this is YUGE: Do NOT fill the crankcase more than 1/2 way between Low and Full on the dipstick. Be sure to check this with the truck leveled!

Now getting 13.5mpg, even with mountain pass climbs thrown in the mix, in full tour mode (~8,000lbs) ... up from 9-10mpg recently before above work. My Columbus RTT and rack account for about 1mpg and the 10000CST silicone stuffed fan clutch account for another 1mpg. So, relatively speaking of course, I'm ecstatic with 13.5mpg (and running Cooper 305/75R18 tires which are known for sucking up another .5 or so mpg).
Click to expand...

Stupid question, I'm sure.... But what is "Cleaning and mapping of the injectors"? I've heard of cleaning the injectors.... Get a kit, hook it up, run the engine, etc... But I've never heard of mapping the injectors.
 
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