# Sudden milage drop **URL:** \ **Category:** Power/Fuel\ **Tags:** audi, a4\ **Created:** [February 17, 2018, 10:51am UTC](https://community.cartalk.com/t/sudden-milage-drop/112379 "2018-02-17T10:51:11Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Gurkamal\_Singh](https://avatars.discourse-cdn.com/v4/letter/g/c2a13f/32.png) [@Gurkamal\_Singh](https://community.cartalk.com/u/Gurkamal_Singh)\ **Post date:** [February 17, 2018, 10:51am UTC](https://community.cartalk.com/t/sudden-milage-drop/112379/1 "2018-02-17T10:51:11Z")
Hello i have a audi a4 2.0t and i am experiencing a sudden milage drop in my car in city i go only around 3-4 km and the on board km thing drops by 10km but on it drop by 10km after 13-14 km i am only having this problem in city anyone know what’s wrong? ---
**Author:** ![insightful](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/insightful/32/2732_2.png) [@insightful](https://community.cartalk.com/u/insightful)\ **Post date:** [February 17, 2018, 6:06pm UTC](https://community.cartalk.com/t/sudden-milage-drop/112379/2 "2018-02-17T18:06:16Z")
Probably nothing. When you start the car, the computer uses its last mpg which was on a warm engine. Short trips in the city use much more gas. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [February 17, 2018, 7:48pm UTC](https://community.cartalk.com/t/sudden-milage-drop/112379/3 "2018-02-17T19:48:05Z")
What year? How many kilometers are on the odometer? Has it been well maintained? City driving is horrible on mileage. That may well be the only problem. ---
**Author:** ![jtsanders](https://avatars.discourse-cdn.com/v4/letter/j/c2a13f/32.png) [@jtsanders](https://community.cartalk.com/u/jtsanders)\ **Post date:** [February 17, 2018, 7:59pm UTC](https://community.cartalk.com/t/sudden-milage-drop/112379/4 "2018-02-17T19:59:25Z")
I notice something similar on my 2017 Accord with the 4-cyl. I’ve seen less than 20 mpg when I first start the car and drive slowly to a highway. As I put on miles at 55+ mph, it climbs to bet than 33 mpg, and often the instantaneous mileage is around 39 mpg. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [February 19, 2018, 1:26am UTC](https://community.cartalk.com/t/sudden-milage-drop/112379/5 "2018-02-19T01:26:59Z")
> [@Gurkamal\_Singh](#): > > sudden milage drop in my car in city i go only around 3-4 km and the on board km thing drops by 10km Are you referring to the km/gallon (fuel usage) reading, or just the km (distance travelled) display? ---
**Author:** ![Gurkamal\_Singh](https://avatars.discourse-cdn.com/v4/letter/g/c2a13f/32.png) [@Gurkamal\_Singh](https://community.cartalk.com/u/Gurkamal_Singh)\ **Post date:** [February 19, 2018, 9:55pm UTC](https://community.cartalk.com/t/sudden-milage-drop/112379/6 "2018-02-19T21:55:26Z")
In city it just goes like 2-3km per letter but on highway it goes 13-14km this started happening after I got my diverter valve changed ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [February 20, 2018, 3:10pm UTC](https://community.cartalk.com/t/sudden-milage-drop/112379/7 "2018-02-20T15:10:50Z")
> [@Gurkamal\_Singh](#): > > In city it just goes like 2-3km per letter but on highway it goes 13-14km this started happening after I got my diverter valve changed With respect, I can’t understand the post. What “diverter valve” are you referring to? ---
**Author:** ![pyrolord314](https://avatars.discourse-cdn.com/v4/letter/p/6a8cbe/32.png) [@pyrolord314](https://community.cartalk.com/u/pyrolord314)\ **Post date:** [February 20, 2018, 3:17pm UTC](https://community.cartalk.com/t/sudden-milage-drop/112379/8 "2018-02-20T15:17:04Z")
> [@the\_same\_mountainbike](#): > > What “diverter valve” are you referring to? I think he might be referring to a blowoff valve: > **[Blowoff valve](https://en.wikipedia.org/wiki/Blowoff_valve)** > > A blowoff valve (also called dump valve or compressor bypass valve) is a pressure release system present in most petrol turbocharged engines. Blowoff valves are used to reduce pressure in the intake system as the throttle is closed, thus preventing compressor surge. > A key function of blowoff valves is to prevent compressor surge, a phenomenon that would otherwise occur as the throttle is closed in a turbocharged engine. If the turbocharger's compressor wheel is spinning at high speed when the th... @Gurkamal_Singh Did you just have your turbo repaired? If it wasn’t working before but it is now (and you’ve been a little heavier footed on the gas pedal), I could see that causing a milage drop ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [February 20, 2018, 10:22pm UTC](https://community.cartalk.com/t/sudden-milage-drop/112379/9 "2018-02-20T22:22:16Z")
> [@pyrolord314](#): > > I think he might be referring to a blowoff valve: I think you might be right. And the conclusion in your post might also have merit. OP??? ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [February 21, 2018, 2:40am UTC](https://community.cartalk.com/t/sudden-milage-drop/112379/10 "2018-02-21T02:40:49Z")
> [@Gurkamal\_Singh](#): > > 2-3km per letter I presume you mean per liter. If a decrease in km per liter is your primary concern, the most common cause Iis a malfunctioning cooling system thermostat. If the engine is running below its optimally designed for operating temperature, the km/liter result will suffer. That’s the first thing to check. ---
**Author:** ![thurman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/thurman/32/11037_2.png) [@thurman](https://community.cartalk.com/u/thurman)\ **Post date:** [February 21, 2018, 3:07am UTC](https://community.cartalk.com/t/sudden-milage-drop/112379/11 "2018-02-21T03:07:29Z")
Check these components and REPLACE. Check the air filter, change pcv valve and change the oil.