2010 B8 S4 poor gas mileage

[dizzysn]

So I've had my S4 now for about three weeks. Gas mileage at first was fantastic. However I recently put on a CTS intake and heat shield, and have noticed a SUBSTANTIAL drop in fuel economy. I've hit about 98 miles and I'm at the halfway mark on the gas level.

Yes I know that some people will floor the car to hear the supercharger whine. However I've been around fast cars my entire life. I love the sound a supercharger whine, but it's nothing new and amazing to me, so I'm not flooring it everywhere in an attempt to hear the sound.

I've also been doing my own work on my cars for years. I certainly can't rebuild an engine, but installing an intake is one of the simplest things to do. I've already checked the connections and nothing is leaking, and everything is seated correctly. Any idea where I can start troubleshooting this?

[Dr GP]

Check your foot for lead. Put the original intake back on to see if it makes a difference.

[AlaskanAudi]

Exactly how bad is your gas mileage? Mine is about 25mpg on the highway with no lead-footing. I also have a CTS intake.

[dizzysn]

Definitely no lead footing. Filled up 6.43 gallons at 101 miles, which equates to 15.7 mpg. That's obscenely low, and I'd need to be flooring it everywhere. I drive 7.5 miles each way to work, miles of which is highway, in work traffic. There's no flooring it possible. The car doesn't have a MAF, but is it possible something needs to be reset by pulling the battery?

[wootwoot]

Easy fix, remove the intake and watch your gas milage go back up.

Also, having the car for 2 weeks and then modifying it is a very poor basis for comparison when evaluating gas mileage. Your mpg may have always sucked and you didn't realize it.

[seandon_792]

I wonder with the change in season (lower temperature) and very short commute have anything to do with it. Optimal gas mileage isn’t reached unless the cars at operations temperatures which usually take 12 minutes of driving to achieve


Sent from my iPhone using Tapatalk

[theweebabyseamus]

A vacuum leak from install could cause this. Id also pull your spark plugs and check them/the gap as its a new car to you.

[audi_403]

I track fuel mileage and my overall mileage for the last 12 months is 22mpg with a well maintained engine, silicone intake and stock air filter.


Sent from my iPhone using Audizine (http://r.tapatalk.com/byo?rid=87676)

[dizzysn]

Easy fix, remove the intake and watch your gas milage go back up.

Also, having the car for 2 weeks and then modifying it is a very poor basis for comparison when evaluating gas mileage. Your mpg may have always sucked and you didn't realize it.

I had the same ride to work for two weeks, as I did last week and this week. I went a week and a half between fill ups, while doing some extra driving around. I was at 3/4 tank when I filled and about 280 miles on the odo. Last week, I filled up 1/4 a tank at 96 miles. It's a significant, and noticeable difference, regardless of the short amount of time I've owned the car.

[kanekhou]

I have the same issue. 2011 S4 B8, I've noticed the last few weeks, I've gotten only 3-4 days and needed a fill up. This week, I tracked it from full tank, and in 1 day I am at a 1/4 tank and have only traveled 44 miles. Let me know what you find out!
Let me know if you have a plan of attack.

[MrFunk]

Calculate your mpg's over a couple fill-ups.
My average is 18mpg over the last 6 years... often have a tanks where I get in the 15's.
Do you park outside? Has temps been dropping? Cold starts use a lot of fuel.

[kanekhou]

I noticed my terrible MPG in the last 2-3 weeks, where I would have to get fill ups twice a week, when normally I would only need one for a week. I only use the car to go back and forth from work. No racing, or high speeding etc...

Yes, I park outside, the temperatures have been dropping, but I don't warm the car up like some people. 15-30 seconds after starting, I'm off to work. Now that I am tracking it, I will jot down how much I get from full to when the light comes on. We'll see how much a tank gives, and I will let you guys know. One thing to note, I've had the car for 4 years, and have only noticed poor gas mileage over the last few weeks. I've had an intake since week one.

[Tweakophyte]

I live around 22 mpg most times of the year... My commute is on the highway with the first half being steady state around 75mph and then the last part being in traffic (slow merge back up to 65).

On the commute in I usually floor it... nice curve to get on the on-ramp and acoustics to hear the car.

[dizzysn]

Update - since the fill up after I posted this thread, I've driven my same daily commute, with some extra city driving around. I've had no change of driving habits whatsoever, and where last time I filled up at half a tank at 98 miles, I've just hit half a tank at 156 miles. So it was absolutely something with the intake. I checked for vacuum leaks on Thursday, but there were none. So I believe there was some sort of "re-learn" that the ECU needed to do.

[kanekhou]

Good to hear you go to the bottom of it. Let us know how the relearn went, and where you're at.

[kanekhou]

I live around 22 mpg most times of the year... My commute is on the highway with the first half being steady state around 75mph and then the last part being in traffic (slow merge back up to 65).

On the commute in I usually floor it... nice curve to get on the on-ramp and acoustics to hear the car.

22 is the scope. These cars were based on 17 city / 27 highway...

[kanekhou]

I noticed my terrible MPG in the last 2-3 weeks, where I would have to get fill ups twice a week, when normally I would only need one for a week. I only use the car to go back and forth from work. No racing, or high speeding etc...

Yes, I park outside, the temperatures have been dropping, but I don't warm the car up like some people. 15-30 seconds after starting, I'm off to work. Now that I am tracking it, I will jot down how much I get from full to when the light comes on. We'll see how much a tank gives, and I will let you guys know. One thing to note, I've had the car for 4 years, and have only noticed poor gas mileage over the last few weeks. I've had an intake since week one.

Final numbers are 186 miles, and refill to 13.3 gallons, which equates to 13.7 mpg..

This past weekend, check tires, they were at 34psi, corrected them to 41psi. Oil change (5000 miles), and added a carbon intake pipe just because they were on sale at ECStuning. @ the 1/4 tank mark it is at 62, where as it was 44 last time. So far so good.

[dizzysn]

Final numbers are 186 miles, and refill to 13.3 gallons, which equates to 13.7 mpg..

This past weekend, check tires, they were at 34psi, corrected them to 41psi. Oil change (5000 miles), and added a carbon intake pipe just because they were on sale at ECStuning. @ the 1/4 tank mark it is at 62, where as it was 44 last time. So far so good.

Hopefully the problem is solved for you too!

[kanekhou]

Hopefully the problem is solved for you too!

Had to get gas today. Looks more normal.
291.9 miles on 14.67 gallons = 19.89 mpg 50% better...

One thing I did that I did not mention. You, @dizzysn, had mentioned a relearn period, which got me to thinking about the ECU. I unplugged my battery for about 2 hours, put my key in and tried to start to ensure there was no residual power. Then hooked it back up. Thought process was that if there was anything in the ECU that may have caused incorrect fuel/air ration, that would help clear the cache. One more thing I'm going to try 89 No Ethanol gas with octane booster (to get it to 91) and see if it gets better; or attempt to find a gas station that sells 93 without ethanol.

Read up on Ethanol gas, and it looks like it was not until 2012 that it was a normal standard/requirement. Since my car is a 2011, I wonder if Audi engineered to run on cleaner fuel, and not think of the fuel requirements coming down the road. Reading the manual, Audi only requires 91, but since in the US there is 89 and 93, technically running 93 should give us better gas mileage and power right?

[nick0188]

Yea, I get 100 miles to 3/4 of a tank. You seem to be doing well. Haha.

[dizzysn]

Yea, I get 100 miles to 3/4 of a tank. You seem to be doing well. Haha.

Holy shit what do you have done to your car?!?! Nearly all of my travel is in moderate, but moving, traffic so I can't beat on it or floor it anywhere without rear ending someone.

[nick0188]

Holy shit what do you have done to your car?!?! Nearly all of my travel is in moderate, but moving, traffic so I can't beat on it or floor it anywhere without rear ending someone.

Basic dual pulleys and bolt on with a ported blower. My driving is city, but I’m on it a lot.


Sent from my iPhone using Tapatalk

[kanekhou]

Basic dual pulleys and bolt on with a ported blower. My driving is city, but I’m on it a lot.


Sent from my iPhone using Tapatalk

Sounds like you're getting great gas mileage for being "on it a lot"!