MPG/Performance loss?

2022, V4, SR5, TSS Off-Road, Pedal Commander City Mode +2, bought at 66k miles. Upon purchase, the dealer said there were no issues with the truck, I had Yota tech check it out. Up until about 72k miles I was getting around 24-27 MPG and quite a few times getting 30, 420-430 miles on a full tank. Maintenance soon light came on around 72K miles. Then a few weeks after that Required came on. Seems like, suddenly, the day the required light came on, my MPG dropped somewhere to 16-20 and around 380 miles on a full tank. And even when the commander was still at city mode +2 I had to hit the gas to get it up to speed.

Serviced at the Dealer, cleaned fuel injectors, changed oil, rotated tires, and changed rear diff fluid, dealer said everything else was good. The required maintenance light is off, but for a few weeks after that, the MPG was still not what it used to be, the tank did last as long as it used to and performance was slow. That was about 1 month ago, but now it seems the performance is getting back to how it was when I first bought it, I can see my average MPG per trip/tank is increasing but not like it used to be. I am averaging about 21-23MPG and about 401 miles on a full tank.

My question is, is it just me or does the computer throttle down the engine and its parts when a required maintenance light comes on, As soon as the maintenance needed soon light changed to required I could notice the difference, like night and day. And why when the maintenance that was required was completed was the performance not like it was right after I bought it?

The only additives I put in it right after I bought it was B-12, and Seafoam. I am not carrying a heavy load, I am not an aggressive driver, no hard stops, starts. Pedal commander does work as I change mode so does the response.

 

24-27 is much much higher than most,, if not all see. If you are really getting over 20mpg, I would be elated with that, that's still well above the norm.
No, I highly doubt the "maintenance required" warning does anything, but just that. Manufacturers are highly penalized/incentivized to get every MPG they can, so they aren't going muck up their numbers, the maintenance is on the owner.

 

Whats your climate like, are they just changing to winter gas? And/or have you tried filling up at a different (busier) gas station?

 

Maintenance pops every 5K miles , it won't know if you changed oil or anything, it is manually reset.

Did you happen to change any driving habits? like instead of highways, traffic. Or instead of warm weather, now its cold weather. Anything with tires like PSI ?

 

Yea I did buy it in August, so it was hot, now it's January it is cold. I am in the deep south of the US. I still drive the same route, and where I am, its pretty rural so speed limits are 55-75 when very few red lights. I did not know there was a thing as winter gas, learned something new every day. The PSI has probably changed since I bought it. I see what you mean in that graph, and you are right the MPG is not a big deal unless it drops a lot. You right I am not filling up at a busy station, does that mean the gas that is being delivered is changed out more often, and more potent?

 

Yea it is probably weather, its for all the cars. The PSI on tires drops, the temperature outside is colder so engine works harder and MPG drops. In warm weather MPG is always better. As far as Gas goes, just use any top tier like Exxon Mobil, Shell, BP , Sunoco. Don't use any cheap garbage and its fine

 

Also factor in the truck has the worst mpg cold as the computer is heating up the catalytic converter so my 0.9 mile trips to school in the winter get me like 12mpg... but once it warms up I'm back to 20. Wish I had your 27 but I've almost never seen that high on my 4 banger.

 

Ya the temperature has a big impact on MPG. strictly temp speaking I was drinking 13.2L/100kms a couple days ago to work when it was -4*C outside but today it was -26*C and that number worsened to 15.6L/100kms.

Colder air is also denser so yes as stated above the tire pressure will drop as the air inside the tire condenses. I believe every 4*C equals a 1 psi temperature change and if your truck is like mine suggesting a 29psi tire pressure then although small, the further pressure decrease can have quite a surprising effect on fuel economy.... I prefer around 32psi but thats a separate discussion.

You are correct on the reason for a busy station, more frequent filings mean "more potent" gas. Gas (especially with ethanol) absorbs water from the air which basically reduces the potency. A fun demonstration of that is to get a small glass jar, fill it half full of gas and just leave it for a few hours in your garage, outside or where ever then check on it periodically. In a few hours it'll start to look cloudy from the water it's absorbing. In my opinion these trucks are very sensitive to bad gas.

Winter gas is essentially a gas that combusts easier/ is more volatile to allow for easier combustion in colder weather. The main drawback is that there is less energy in a molecule of winter gas vs. Summer gas so you need to burn more winter gas to compensate.

For now check your tire pressure and maybe switch to a busier gas station then reassess in the spring/summer

 

This sounds like a job for Tim the tool man Taylor

 

I think your mileage computer was temporarily set on kilometers or had some other glitch because that mileage is way, way higher than everyone else with the same SR5 and 4 cylinder engine. Since you mention 401 miles/tank is what you used to get, that works out to 19.1 mpg since the tank holds 21 gallons. That 19 puts you right there with expected 2.7L mileage.

Joe

 

Not to pick a nit, but there is no such a thing as a Tacoma with a V4 engine; what you have is an I4.

Absolute waste of money.

Regarding your poor fuel economy, a few thoughts:

1. Cold air during the winter will virtually always reduce fuel economy to a certain degree.
2. In certain parts of the country the winter blend of fuel will also contribute to lower fuel economy.
3. While I don't hear of it too often on either engine available in the Gen3 Tacoma, upstream O2 sensors sometimes get lazy; not lazy enough to throw a code, but enough to cause a reduction in fuel economy.

In your shoes I'd wait for warmer weather to see if your economy comes back up.

 

Mine lost an mpg or two after diff fluid change in both diffs. OEM fill is 75w85 and dealer probably used 75w90. The more viscous fluid is even more noticeable in winter/colder months. After 70k, your OEM fill was probably thinner from breakdown over time so you got better mileage.