List of primary wear items that affect MPG

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yuji

yuji

10 Year
Joined
Mar 11, 2012
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Location
Portland, Oregon
The thread about fuel injectors and MPG made me wonder what the primary wear items are that affect MPG, why, how often they might need attention, and finally estimated importance / impact.

I realize lots of MPG stuff is voodoo so I'm not sure how to keep this as factual as possible.. but I'm still curious what the list would look like. Let's stick to OEM COMPONENTS to keep gadgets out.

No additives, driving techniques, etc.


I'm curious because my MPG is way too low. 6.5-8.5 city. Bout to put on front bumper, winch, rear bumper, spare tire, and sliders. Can't imagine what will happen.

I'll start here and update.


What: Low Tire Pressure
Why: Low pressure causes more friction
Lifespan/Interval: ?
Impact: Ridonculous


What: Mass Air Flow Sensor (MAF)
Why: Determines fuel mixture
Lifespan/Interval: ?


What: Throttle Body
Why: ?
Lifespan/Interval: ?


What: O2 Sensors
Why: Regulates fuel mixture w/ MAF
Lifespan/Interval: ?


What: Intake leak
Why: Could cause incorrect air/fuel mixture, esp if leak is after sensors.
Lifespan/Interval: ?


What: Exhaust leak
Why: ?
Lifespan/Interval: ?


What: Fuel Injectors?
Lifespan/Interval: ?


What: Fuel Filter
Lifespan/Interval: ?


What: Air Filter
Lifespan/Interval: ?


What: PCV Valve
Why: ?
Lifespan/Interval: ?


What: ECU Reset
Why: Because the ECU learns how to run your engine based on sensor readings / may have anomalous data or not caught up to a recent mod.


Please post if there's reason for or against items listed / new additions. After I get my gear on my truck this weekend, I'll be going through this list with a fine toothed comb.
 
Last edited:
As far as intervals go, I try to clean my MAF, air filter (oiled), and throttle body with every oil change. I probably check my tire pressure about as much or every time I air them back up after a trip that has taken me off road.

The weight of your engine oil will also effect your MPG's. I can still run M1 0W-30 in my 170,000 mile old engine without burning any. The thinner the oil the more easily the crank and associated parts can turn, ergo better MPG. The effect although present is barely noticeable so I doubt the same would apply to the transmission, diffs and t-case.

I know it is not a maintenance issue, but aerodynamics are also huge at highway speeds. When you put large and bulky parts on your truck like a roof rack, expect to see more drain, regardless of how light it may be.
 
* Catalytic converters get clogged more as they get more miles on them and cause more back pressure, less power, use more fuel.

* Mufflers also get more buildup as they get older, and cause more back pressure, less power, use more fuel.

* any loose body panels that cause wind resistance

* transmission fluid, engine oil, diff fluid, etc...

* dragging brake pads from old brake hardware that is not "springy" anymore

* dragging ebrake if cables not adjusted properly

* roofracks and rear hatch spoilers are bad for MPG

all i can think of off the top of my head.
 
Spark plugs. Every 100k miles or so.

Tire pressure. Run it high as you can stand. Low tire pressure kills your mileage.
 
Anyone have any suggestions on how to narrow these down / rate them better for myself and others?

For example.. impact / likelihood at a given mileage perhaps? 50k, 100k, 150k?

At 150k, XYZ are the top things to look at. Open to suggestions... we need a stackoverflow.com-like voting system so we can vote the consensus to the top!
 
Wow. That mileage sounds really low for a totally stock truck. Something isn't right. I would sort that out before adding all that other stuff on, which all has a negative effect on mileage.

Try cheap easy things first.

Have you been running high quality, brand name gas, or the random stuff sold at the local convenience store? I ask because the cheap gas eventually clogs up the injectors. Run some good injector cleaner like Redline Fuel System Cleaner. Maybe run one bottle, and then another, with only about 12-15 gallons in the tank (higher concentration). The PO of my 80-series ran cheap gas. I even pulled the injectors and had them ultrasonically cleaned at the local diesel injection shop. Results were night and day in terms of how it ran.

Then I replace things proactively like air filter, fuel filter, spark plugs (100k mi), O2 sensors (100k mi.), clean the intake and MAF, reset the ECU (disconnect battery) and see where you are after driving it for a few tank.

Make sure you don't have exhaust / cat blocked. (Heck....I reaching, but it could be something crazy like that)

Best of luck
 
super90 said:
Wow. That mileage sounds really low for a totally stock truck. Something isn't right. I would sort that out before adding all that other stuff on, which all has a negative effect on mileage.

Try cheap easy things first.

Have you been running high quality, brand name gas, or the random stuff sold at the local convenience store? I ask because the cheap gas eventually clogs up the injectors. Run some good injector cleaner like Redline Fuel System Cleaner. Maybe run one bottle, and then another, with only about 12-15 gallons in the tank (higher concentration). The PO of my 80-series ran cheap gas. I even pulled the injectors and had them ultrasonically cleaned at the local diesel injection shop. Results were night and day in terms of how it ran.

Then I replace things proactively like air filter, fuel filter, spark plugs (100k mi), O2 sensors (100k mi.), clean the intake and MAF, reset the ECU (disconnect battery) and see where you are after driving it for a few tank.

Make sure you don't have exhaust / cat blocked. (Heck....I reaching, but it could be something crazy like that)

Best of luck
Click to expand...

Not totally stock - happened after Toyo MTs, spark plug, oil change + transmission fluid. This was also 2 weeks after EMS Exhaust.

I'll pull a plug soon and see what it looks like since that was clearly changed recently! I also feel the exhaust smells rich.. but I don't have a baseline to compare to.

The roof rack has also robbed about 2 MPG for the past 6 months. So 12-17 stock gone to around 7-10.

That said though, I still believe it's too low. I read built trucks (add at least 600 lbs vs mine), same tires, EMS Exhaust, and never have I read 6.5 even by self proclaimed lead footers.

That said I understand I probably drive in the city more than others.

Ordered 2 o2 sensors, the fuel injector cleaner, seafoam. I am tempted to pull the injectors for a legitimate cleaning.
 
7-10 is way too low. Clean your maf and throttle body and reset your ecu.
 
OregonLC said:
7-10 is way too low. Clean your maf and throttle body and reset your ecu.
Click to expand...

Will do. Its been about a year.

It's pouring like mad right now... but soon, I will do a huge MPG hunt. Thanks for the second opinion! I generally keep quiet about the MPG since they seem to be *all over the place* depending on driving style and location.

Would transmission failure have anything to do with this? I remember reading in the 2000 failure thread somebody suggesting bad torque converters. That would kill economy and power. I'm actually going to test that. Might make sense why going to 33" felt like such a massive power sink while others say "they barely notice it".

My trans is the one I posted with nice huge flakes :)
 
+1 for the roof rack

I removed my roof rack, replaced the fuel filter, recently changed the spark plugs/engine oil,diff fluids, transmission fluid (all with mobil 1 synthetic), new air filter, seafoamed, cleaned throttle body and MAF sensor and get about 15 MPG mix of city/highway with 285's and a small lift with about 50lbs of gear in the back and third row still installed

and a good reset of the ecu - disconnecting the battery for 30 min and reconnecting, letting it run for 15-20 min at idle and not touching the gas
 
I just replaced my 60K BFG AT's 285/75/16 with new ones, same size, same plies, and lost 1.5mpg.

Rolling resistance seems to be a big deal. I am wondering if my problem is also extra height?

I was really surprised.
 
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