What could have caused the truck to lose gas mileage and feel sluggish

I recently noticed that my truck has been getting worse gas mileage and feels a lot more sluggish. I dropped a bit of weight in the truck after noticing and it hasn't really changed. Previous to noticing the change I was getting 14L/100KM. Then I was suddenly getting 16-17L/100KM

The gas mileage could partially be due to a change in my commute which went from 30 min 90% highway to 20 min 20% highway. Definitely a lot more start and stop than before, but the change seemed to happen a few weeks after my commute changed. I also thought it could be the winter fuel blend but I have never noticed such a drastic change before.

Regarding the sluggish feeling. I feel like the truck doesn't have as much pep as it did a month ago, not that Tacomas have much pep in the first place. I had my battery crap out recently and I replaced it. I have also heard that I am getting near the time when I might want to do my spark plugs(100,000KM). Could weak plugs cause a lack of power and potentially worse gas mileage? Also I haven't thrown any codes in the last few months.

Thoughts?

 

Plugs are due, but the fuel mileage is almost definitely related to the higher amount of city driving being done.

 

Unless you idle a lot on traffic, 16-17L per 100 km is really bad for a 3.5L. Are you stock? I’m able to get 12.5-14 in city in my modified taco.

I would clean the throttle body, change the plugs, clean MAF, check air filter, PVC valve, change the plugs and see if that changes anything.

Also I noticed my truck gets about 1L per 100 worse on winter blend fuel.

 

Opening up a can of worms, but what kind of fuel do you use? Plenty of threads on this topic, so let’s keep it light, but some vehicles just don’t run well on specific fuel.

 

Check your tire pressure

 

One of my observations is that the fuel mileage sucks until the engine & trans are up to normal operating temperature. Your change in driving habit accentuates that phenomena. Not knowing your definition of 'highway' may matter. If I drive the interstate highway (≥65 mph/105 km/h) my Taco's fuel mileage starts to improve about 5-10 minutes at highway speed. If I'm on local roads/highways (<60 mph/95km/h) it takes about 10-15 miles. A consequence for you is that a greater portion of your drive time is before you get to optimum fuel efficiency.
Also factor in the Winter fuel blend AND how you use the skinny pedal in stop & go conditions as well as the typical ambient air temp.
All of the above are likely the major contributions to your reduced fuel economy.

 

fuel quality. my truck is very sensitive to bad fuel. also, my truck will start to feel sluggish when i don't do any highway driving. i think it's due to the transmission "learning" your new driving style which is being stuck behind traffic (not a fun driving style).

 

Welcome to TW, where your mileage drops just by joining it!

Dirty or bad types of air filters and oil changes to the wrong viscosity can lower mileage too.

 

Stock engine and trans, I have a canopy and rack but those aren't new. Plugs will definitely be getting changed but need to source them and find the time to do them myself. From what I've gathered about the Tacoma engine it is a complete PITA vs inline 4 engines I have had in the past. I'll likely be starting with the PCV valve, cleaning the MAF and replacing the filter and going from there.

87 Octane, nothing fancy

Tire pressure is normal and has been calibrated for the change in season.

 

I more meant what type of fuel. Top tier, Shell? Chevron? Or do you go no name, “USA Fuel” or something.

Is there any parallel between where you bought gas and fuel economy?

 

Poor fuel mileage could be anything from a dirty air filter, plugs, to low tire pressure. High mileage engines can even be old 02 sensors, or a dirty mass air sensor.

 

Man that’s nothing I have a 5 mile round trip to work and I get 11 mpg. Short drives on these trucks will kill your mpg.

 

Check tire PSI.