Why did my MPG go down

All of your mods are the exact reason. You've taken an 18 (city) 22 (hwy) 20 (combined) mpg stock truck, added weight, worsened aero, and added rotational mass - 18-19mpg after mods is about par. Also to be noted, because you've gone up in tire size, the odometer is not accurate; therefore your displayed mpg is not accurate. If you're not calculating exact mileage using the difference in tire diameter of your larger tires vs stock, you'll never know your "correct" mpg. Although it won't give you 2 mpgs back, that fraction of a difference may be enough to close the gap of you thinking somethings wrong with your truck.

Side note, its time for spark plugs. Its not going to hurt, thats for sure.

 

its funny that you are crying about 19-20 mpg carrying around all the crap, maybe your engine is just getting tired

 

18-19mpg for a Tacoma is decent. There's other things to focus on in life.

 

I get all that. My question is really why after all those mods when I WAS getting 20+ I no longer am. I'm going to guess that for now it maybe a maintenance issue and new plugs, fluid or something might be the issue. I guess we'll see.

 

^this^
get a hobby
i like porn

 

Jesus, who's crying. I'm just exploring an issue that's relevant to me. If you can't help then fuck off.

 

When was the last time you replaced the engine air filter? (How many months/miles since last changed?) Same question for the PCV and hose. Mine (PVC) had about 50,000 on it and was gunked up but not completely blocked. I got a slight MPG increase and better idle performance after I swapped them out. YMMV

 

help:
-tires at 35psi
-put engine on a diagnosis machine
-therapy

 

I'd be tempted to do some OBD data logging and check things like the long and short term fuel trims. then at least you'll know if the computer is trying to compensate for something?

Years ago I had cracked exhaust manifold on a different vehicle, which was letting air into the exhaust, which was getting picked up by the o2 sensor and telling the computer it was running lean, so the computer (a dumb, mid ninties one), was dumping fuel in and making it run rich. Garbage in, garbage out.

 

Oh, snap. Good question. It's probably been 40K or more ago. Maybe I should do that first. Thanks for the reminder.

 

I'll bet that's it.

 

It’s gotta be oxidized blinker fluid!

 

Truck is 7 years old and has almost 100K miles? Has it ever been checked over diagnostic wise??

It would stand to reason the engine has some wear and isn't as efficient
as it was when it was new. The air cleaner should be changed out for sure.

If mileage is really that big of a deal then get something smaller like a 4cylinder to daily drive?

 

It could be anything really. Common sense points to mods making it less efficient, but that doesn't mean there can't be something underlying. Outside of blaming mods, my next finger to point would be at general maintenance items. Parts wear, fluids break down, things become less efficient over time if not properly maintained. Start simple, do the maintenance that needs to be done (sounds like an air filter and spark plugs is a good place to start) and go from there. With no major symptoms or ability to provide us with any kind of data, theres nothing thats going to scream that anything is actually wrong, and getting 18-19 mpg with a modded truck, it honestly sounds like its doing really well.

Use the ignore feature; it does wonders.

Its extremely possible your engine is starving for air. Its also extremely possible your filter is clean enough to eat off of. A few $ is worth the replacement either way.

 

Winter fuel blend does effect your MPG, mine normally drops 1mpg on average.

https://fox59.com/news/national-world/winter-gas-is-returning-what-does-that-mean-for-your-wallet/

 

I've noticed a drop in mpg after putting my Ranch cap on. Didn't think I'd notice a difference but I did drop 1 or 2 mpg.

 

same topper, same results. It sits just a bit higher than the cab (wind resistance adds up fast!) and a couple hundred pounds of semi permanent weight.

 

toppers also create a large negative pressure space behind your truck which will affect mpgs

 

Wish I could average 18 mpg