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Sazexa
01-03-2018, 02:38 PM
Hey guys, as the title says I've noticed a sudden, and rather large, drop in fuel economy. I have no engine codes, and everything feels to be running fine. The car feels about as fast as always. I had my car down for about two weeks, waiting for a clutch slave to come in. The temperature before it came in was anywhere between low 30's to low 40's. Now that the part has been replaced two weeks later, and the temperatures are a bit colder now (some days single digits, today was closer towards mid 20's), I've noticed my at my last fuel up I had almost 100 miles less of range on the tank. I don't think I've been driving extra aggressively. The temperature alone can't be responsible, can it? Again, no engine codes. Just looking for ideas. My last fill up was after about 190 miles on the tank, usually I get around 265-280, and that's me gassing up at 1/4 tank.

11S5V8
01-03-2018, 02:57 PM
I have an auto get about 310 per tank. I use nothing but the highest grade of gas and I avoid shitty gas stations. I can't imagine anything is wrong if no CEL light is on.

Audibot
01-03-2018, 03:15 PM
It's probably the switch to winter blend of gasoline. I've noticed a drop myself. Even from the highest tiers, they all have additives to prevent gelling and other conditions, mostly meant for places like Minnesota where it will drop enough to affect gasoline.

Bdkxracer17
01-03-2018, 04:15 PM
Probably the weather. Colder air = more fuel. Also like audibot like said winter blend gas. If i remember right winter blend also evaporates quicker then summer blends

Sent from my SM-N920T using Audizine mobile app (http://r.tapatalk.com/byo?rid=87676)

Sazexa
01-03-2018, 05:07 PM
I have an auto get about 310 per tank. I use nothing but the highest grade of gas and I avoid shitty gas stations. I can't imagine anything is wrong if no CEL light is on.
Autos are a bit less high-revving. But I stick to the major brand companies for my gas, such as Sunoco mostly, and always put 95 Octane in. No CEL, but, that doesn't always mean everything is running exactly as it should.



It's probably the switch to winter blend of gasoline. I've noticed a drop myself. Even from the highest tiers, they all have additives to prevent gelling and other conditions, mostly meant for places like Minnesota where it will drop enough to affect gasoline.
You know, I didn't even think about this. That could very well be a reason why.



Probably the weather. Colder air = more fuel. Also like audibot like said winter blend gas. If i remember right winter blend also evaporates quicker then summer blends

Sent from my SM-N920T using Audizine mobile app (http://r.tapatalk.com/byo?rid=87676)
Yeah, it doesn't help mine seems to run slightly rich in normal weather conditions also.


EDIT: Maybe this will become a semi-long term post that I update in the warmer months and see if the mileage reverts.

ICU2
01-03-2018, 07:19 PM
Autos are a bit less high-revving. But I stick to the major brand companies for my gas, such as Sunoco mostly, and always put 95 Octane in. No CEL, but, that doesn't always mean everything is running exactly as it should.



You know, I didn't even think about this. That could very well be a reason why.



Yeah, it doesn't help mine seems to run slightly rich in normal weather conditions also.


EDIT: Maybe this will become a semi-long term post that I update in the warmer months and see if the mileage reverts.
In addition to the already mentioned, R U “warming up” your car for a couple minutes each AM before driving? May account for some overall drop in total miles per tank. 🤔

namvar
01-03-2018, 08:09 PM
I would not panic on just one tankful. keep an eye on it thought.

Some specifics on the car may be helpful. ie what engine do you have.

Sazexa
01-04-2018, 05:23 AM
In addition to the already mentioned, R U “warming up” your car for a couple minutes each AM before driving? May account for some overall drop in total miles per tank. 🤔
when I start the car in the morning I typically wait until the engine idle has dropped from the higher cold-start speed to a more reasonable sub 900 RPM idle speed.


I would not panic on just one tankful. keep an eye on it thought.

Some specifics on the car may be helpful. ie what engine do you have.
It's a 4.2L V8, on a S5.

AWDfreak
01-04-2018, 04:23 PM
I have the 4.2 in a 2012 S5. I typically fill up at about 200 miles 12-13 gallons. Mostly local driving and typically get about 17.5 mpg. Have not noticed a significant change in fuel economy as the weather has gotten colder. It has been in the 20s and 30s the last couple of weeks with single digits in the morning this week. On the highway driving with a light foot, I get 23-24mpg and fill up around 275 miles. From what I've seen on the forums, my numbers are typical for the 4.2. Did your trip odometer get reset without you knowing?

UPDATE: Now I have almost finished a tank in the very cold weather, the fuel economy has dropped about 1 mpg from normal.

cts5
01-06-2018, 05:44 AM
I've got a 2010 V8MT in Fairfield County CT - and I'm down 1-2MPG per tank over the November. My average tank is 60% highway and 40% around town or stop/go on the highway and I'm around 20.1mpg, was at 21.5-22.0.

So yeah, I think they changed our fuel blend - nothing else changed on my car.