vchen441

The last tank I went through got me around 155 miles which had 12.4 gallons in it. That is less than 13 miles per gallon.
My average mph is 13 mph as I do deliveries around town, but is this the expected mileage at this speed?
My father used to only use 87 until I started driving it recently, and he used to get like 14 to the gallon.
Could this all be because the AC is constantly running?

BROlando

Its because of the usage.

Heavy right foot because you're in a rush. Car loaded up with stuff(?). Presumably short distances. Lots of idling and stop/go. 87 octane is also a factor. But...the improvement from using 93 is likely not worth the added cost of 93.

Its not ALL because of the AC. But yes using the AC uses gas.

If there's no check engine light on...there's nothing wrong with the car.

vchen441

Alright, thanks! I'll try to drive more conservatively.

mariusz439

Do not expect any better if you drive 20mph in average. That means ride in traffic jams. I get 13-14 in summer and 12-13 in winter in such traffic.

spamcop01

You'll get more educated responses from others in the forum, but the likely culprit is the oxygen (O2) sensors. Your MPG sounds really lousy regardless of how you drive. Take a look at this thread.

https://acurazine.com/forums/third-g...y-crap-962023/

Also, since it appears you're relatively new to the forum, I'll let you know that the native search tool on this site isn't great. Instead, what I usually do is use Google and prefix my search with "site:acurazine.com" (no quotes). For your search, I punched this into Google:

site:acurazine.com o2 sensor gas mileage

If you replace the sensor(s), let us know how it goes. @thoiboi likes to remind people that Bosch sensors suck and to use Denso brand instead. You'll pay more, but it will be worth it. Good luck!

spamcop01

As I learned on this forum when I was researching scan tools, the majority of check engine lights (CELs) are related to regulatory emissions requirements. Perhaps you didn't mean it in a general sense, but there can actually be a bunch of issues or potential problems with your vehicle that won't raise CELs, or will only do so when the problem has become "bad enough" to warrant it.

I could be mistaken, but I believe there are a lot of anecdotal stories and posts by people who've changed their O2 sensors and seen quantifiable improvements in MPG even when they never had a CEL (like in the earlier thread I shared).

There are similar posts about proactively changing the 3rd & 4th gear transmission pressure switches leading to improved and smoother tranny shifts. Again, even when there was no CEL or other Malfunction Indicator Lights (MILs).

thoiboi

hey thanks for doing my job! Your check is in the mail

BROlando

Burning too much fuel for a given situation is related to emissions.

The CEL will turn on if this is the case.

O2 sensors will gradually diminish in effectiveness. But if they haven't diminished to the point of burning more fuel than warranted...there won't be a CEL.

If they're within that threshold, replacing them will only net a MINOR change in MPG. Right?


However...
If he's burning a lot of fuel per mile because of driving habits/situations....then...that's where all the fuel is going.

Let's say I have a car without a CEL, but I want better MPG. I can put in brand new O2 sensor in...and then go floor it to a parking spot 10 miles away and idle for the rest of the tank. I'll get horrendous MPG and 10 miles to the tank. And the CEL would never turn on. Because there's nothing wrong with the car. A new O2 sensor is not the effective cure.

On the flip side, improving my driving habits/situations would net exponentially better MPG, even with old O2 sensors.

Things to note...
The ECU ignores O2 sensors during open loop. Warm up cycles. Agressive acceleration. Those kind of situations.

O2 sensors will best help your constant cruise MPG.

Think of the situational variables that are present when someone puts in a new O2 sensor.

They're observing their MPG
They're actively trying to get better MPG

One might argue that even with new O2 sensors, the majority of improvements come from driving habit improvements

spamcop01

Great points all around, @BROlando , and thanks for the additional info! I was mainly trying to clarify that, generally, just because you don't have a CEL/MIL, doesn't mean that there may not be problems with your vehicle.