How many people smell gasoline under oil cap after driving?

[S6Man4.0tt]

Seems like smelling gas in the oil under the oil cap is common. It's right next to the high pressure fuel pump which are known to have leaking seals and dilute your oil. Also injectors can go bad. I'm wondering how common this is. The 2 4.0's I've personally owned and checked both had the smell. I know alot of people have had real problems and fuel smells where a bad sign.

Be aware the oil cap itself and the plastic right under the cap can really reak from buildup on it but the air coming out isn't as bad. I thought I had the issue bad for sure until I cleaned it. Now I can barely tell there is anything at all.

[MattyMarkey]

Seems like smelling gas in the oil under the oil cap is very common. It's right next to the high pressure fuel pump which are known to have leaking seals and dilute your oil. Also injectors can go bad. I'm wondering how common this is. The 2 4.0's I've personally owned and checked both had the smell. I know alot of people have had real problems and fuel smells where a bad sign.

I'm not sure that a smell of gas means it has an issue either though given how the PCV system is it may be somewhat normal to a degree. In my case I had no issues with driving or starting ect. and logs look fine.

Be aware the oil cap itself and the plastic right under the cap can really reek from buildup on it but the air coming out isn't as bad. I've noticed I can clean this and the smell can goes away from the cap itself and not come back. I'm not sure how much that should count in this case. I can tell the air still has fuel smells in it to some degree a little bit which may be normal.

This may just be me, but thinking a gas smell mixed in with your oil is “normal”, goes against every engineering principle that every combustion engine has been built around.

It does seem like the more people tune their 4.0t cars and go bigger turbos, or other forms of fuel, the HPFP has been failing for a growing number of people. Not sure it’s all that common just yet, but seems to be a growing issue and likely weak point.

This is something you should get checked out. If you have DS1, you can log your runs/driving to determine if you have a potential HPFP leak - fueling would drop at certain points. I believe they also have new “health check monitors” to help determine early on if you have a failing injector. It sounds like you have logs, didn’t know what has been logged.

You can also check out the HPFP itself - take it a part and check for leaks.

If you don’t have the typical PCV failure symptoms - hard to pull oil cap, whistling and oil consumption - I personally don’t think it’s a PCV issue causing that smell in the oil.


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[gk1]

I agree too. Smelling gas in the oil is not "normal".

[S6Man4.0tt]

It’s so common in these and with a lot of cases seeming to have no other symptoms of problems. Both of mine are like this and I think most probably are this way. My thinking goes along the lines of some fuel vapor being trapped in the pcv seeming worse than it is as in not broke yet. It’s not an average system and does a good job being a vapor tank. If everything is perfect on a car sure no smell is ideal but in the real world as cars wear and other issues like running slightly rich, mods, oil dilution related to blow by and imperfect detonation. A slight amount might really seem like a lot when it’s not and built up over time. Both of my cars seemed like an issue with no symptoms and one even more than the other. I learned it’s mostly buildup on the cap and plastic below the cap in the oil port itself in my case though and not so much in the air to none in the air. I got rid of 80 percent of the potency of the smell for sure after cleaning the cap and plastic below it in the oil port to the point it’s a questionably faint smell now or that it’s even there. I need to do this in my other one it’s pretty bad with 12k miles on it but the cap itself reaks and will clean it soon and test. It’s pretty hard to get the smell out of the plastic completely. So clean those till you can’t smell anything then check again maybe you don’t have a major issue that has to be fixed


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[Alabama]

I agree too. Smelling gas in the oil is not "normal".

Again, please help me out understanding this. I frequently raise the hood after driving to allow the engine bay to cool better. I never smell gasoline. If everything was running OK, why would I ever want to remove the oil cap? Or are you folk referring to diagnosing a recognized problem (e.g., VCDS error code)?

[S6Man4.0tt]

Again, please help me out understanding this. I frequently raise the hood after driving to allow the engine bay to cool better. I never smell gasoline. If everything was running OK, why would I ever want to remove the oil cap? Or are you folk referring to diagnosing a recognized problem (e.g., VCDS error code)?

It's not under the hood that you smell it. Its if you take off the oil cap. I think a little gas smell in this case doesn't mean you have a major problem, as long as it's not much. Common on older 4.0 the fuel pumps leak and leaking injectors as well it seems all the way through 2016 at least. When you take off the oil cap and it smells it can mean you have those problems because you will smell unburned gas inside of the PCV system. People like to check once they learn this because your car can run a long time with leaking pumps ect before it throws a code or if you buy a car or something. It dilutes your oil without you knowing it and can lead to more engine wear and carbon buildup.

[gk1]

Again, please help me out understanding this. I frequently raise the hood after driving to allow the engine bay to cool better. I never smell gasoline. If everything was running OK, why would I ever want to remove the oil cap? Or are you folk referring to diagnosing a recognized problem (e.g., VCDS error code)?

When I change my oil I smell for anything funny...common practice. Never smelled gas in the oil in my cars...hence not "normal"...for me anyway.

[Alabama]

When I change my oil I smell for anything funny...common practice. Never smelled gas in the oil in my cars...hence not "normal"...for me anyway.

Right. Remove cap only at the time of oil change and inhale at that time. No gas smell in oil so far in this car either. As MattyMarkey wrote, the thought that gas in the oil is common or normal in an "all OEM" car doesn't pass the sniff test.

[S6Man4.0tt]

I guess a better word than 'normal' would be non-detrimental but not ideal. A little bit of fuel vapor in a PCV doesn't mean there is a major issue in another words. Unless it's heavy that is. I could be wrong though just a thought. I've seen other people who can smell it and I think it builds up on the cap slowly over time at higher mileage. It reaked at first then I cleaned it now I can barely smell gas at all. I can't tell anything is wrong from logs or anything else. A tiny bit of fuel probably goes a long way to smell it in a PCV so maybe a little bit of blowby or something which one would expect at miles. "relatively normal" Don't even know if it can be avoided. But this is all in theory. Would be nice if it had none.

[MattyMarkey]

I think we are going to agree to disagree with our differences in thought process on this one.

I’ve personally never smelled it under my oil cap, including 30min ago. Hope I never do, but if I do, I will definitely look into it and/or get it checked out.


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[ichi d]

I smelt gas in my oil but I had a failing hpfp. After I replaced both pumps and did a oil change the smell was gone. So to me it’s not normal if you are smelling it.

[S6Man4.0tt]

I edited my post. Either way I don't want to spread bad info or confuse people and I see it could now.

[Audineil]

If you smell gas in your oil you have either a leaking hpfp or leaking injectors. Like said already, you can have this issue for quite some time before it throws a fault. The fault is usually rich at idle. If it gets bad enough it can also cause your car to start hard. As in crank a lot before actually running. Especially if it sits for a good amount of time.

[AudiA72011]

Hey guys. I bought the HPFP for my car with parts number 079 127 025M. But on my car is 079 125 025T part number from the sensor. Do you guys think it will still suit to my car? Or do i have to unbolt the old sensor and install it on the new pumps?

[Bkscooby]

Hey guys. I bought the HPFP for my car with parts number 079 127 025M. But on my car is 079 125 025T part number from the sensor. Do you guys think it will still suit to my car? Or do i have to unbolt the old sensor and install it on the new pumps?

I reused the sensor from one of the pumps. Mine came without it. Not sure on the part numbers. Pull the cam roller, if it spins freely - change it. I didn't have to. Normally you would get codes if the cam follower is bad and the car would not run well. If all you're having is a hard start, fuel in the oil - it's likely the pumps. Make sure to change the oil once you're done.

[jacobyb]

Is this a serious thread???? You smell gas in your oil...? You mean the same oil that mixes with gas on every single combustion stroke of your 4 stroke V8 engine? Over the course of your 3-5K mile oil change interval? Jesus Christ...

[jacobyb]

Also, for the O.P. A lot is 2 words. Alot is not a word.

[S6Man4.0tt]

Is this a serious thread???? You smell gas in your oil...? You mean the same oil that mixes with gas on every single combustion stroke of your 4 stroke V8 engine? Over the course of your 3-5K mile oil change interval? Jesus Christ...

I was thinking the same thing at first. I've had 2 4.0's both had leaking HPFPs one at 13k miles. The pump seals leak directly into the engine you don't want that for sure in any quantity. This isn't a small amount of "normal" oil dilution (which isn't good or ideal anyways. Sure I get less than 1 percent dilution but this could be more easily. Also injectors get stuck open. If you smell gas in the oil it could be a sign of either of these and was in my case. They redesigned the pumps a number of times so I assume this is another fairly common deal at least on the older years 4.0. It seems like alot of people had these issues and it led to starting problems too.

[AudiA72011]

IMG_3076.jpg
I opened oil cap today and look into the engine place and it has this yellow fluid in it. Is that because of mixing fuel with oil? I change the HPFP two days ago and just did the oil change. Is it possible that is still has got a little fuel in the motor? It stiss smells a little bit of fuel but ist not that strong like it was before i changed the HPFP. I didnt change the oil filter because i made a oil change with oil filter about 500miles ago.

[S6Man4.0tt]

IMG_3076.jpg
I opened oil cap today and look into the engine place and it has this yellow fluid in it. Is that because of mixing fuel with oil? I change the HPFP two days ago and just did the oil change. Is it possible that is still has got a little fuel in the motor? It stiss smells a little bit of fuel but ist not that strong like it was before i changed the HPFP. I didnt change the oil filter because i made a oil change with oil filter about 500miles ago.

It's just oil residue and if there is enough fuel vapor it could be mixed with fuel. So it could trick you into thinking there is still a leak. Like I said above I cleaned both of mine. One I was able to clean the smell out and thats what it was mostly was just buildup sitting on the cap from 96k miles. The other it made no difference after 30 minutes of cleaning it and it reeks no matter what. I need to put the new pumps on but waiting for cam rollers. Hope it's not the injector at 13k miles

[AudiA72011]

It's just oil residue and if there is enough fuel vapor it could be mixed with fuel. So it could trick you into thinking there is still a leak. Like I said above I cleaned both of mine. One I was able to clean the smell out and thats what it was mostly was just buildup sitting on the cap from 96k miles. The other it made no difference after 30 minutes of cleaning it and it reeks no matter what. I need to put the new pumps on but waiting for cam rollers. Hope it's not the injector at 13k miles

Yeah i think its normall to smell a little fuel in the oil i think.

[QuattroJ]

I noticed this on my B8.5 S4 the first time I changed the oil. The smell isn't over powering but it caused concern none the less. After researching it, it seems to be a by product of direct injection. Audi indicated the same thing. I don't have any codes and the injectors aren't leaking. This is my first direct injection engine so I'm hoping Audi is correct.

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[S6Man4.0tt]

I noticed this on my B8.5 S4 the first time I changed the oil. The smell isn't over powering but it caused concern none the less. After researching it, it seems to be a by product of direct injection. Audi indicated the same thing. I don't have any codes and the injectors aren't leaking. This is my first direct injection engine so I'm hoping Audi is correct.

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Can be true to a slight extent IMO, but the thing is a lot of the time it's not. There are a number of people who smell none which seems to be ideal and it was fixed after it smelled. There is a lot of cases fuel pumps leaking into the engines and stuck injectors so don't think its just normal necessarily. I think if it's a trace amount it might be ok enough then. But if a heavy amount of gas smell is coming out of your oil you will know it and it's a problem.

Audi is crap about these cars so I wouldn't listen to them. They want to cover their ass and not fix cars unless you get one of the mechanics alot of information from audi service people isn't going to be right about these cars.

[S6Man4.0tt]

Well I changed my hpfps last night. There where equal puddles of fuel in and all over the cam rollers and both of the pumps where washed out. Drove for 20 minutes to test and cycle the diluted oil. When I started it this morning it was like a miracle no more crappy lifter sounds at first just smooth. I changed the oil today into a 5 gallon bucket it reeked of gas heavily. This car is a 2014 with 14,000 miles only so age can do it too and it had an incredible one owner maintenance record by date every year and through 45k Audi services. They did 45k service at 11k miles. It was just inspected by Audi Miami before I bought it too and they also missed an obvious severe case of 1k/3k vibration. Hoping no engine damage this stuff could go years without people knowing it. Had two cars with this problem and both had zero codes or signs externally.


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[QuattroJ]

Thats good to know. Ill have to recheck mine. Did you notice any decrease in fuel economy?

[MattyMarkey]

Well I changed my hpfps last night. There where equal puddles of fuel in and all over the cam rollers and both of the pumps where washed out. Drove for 20 minutes to test and cycle the diluted oil. When I started it this morning it was like a miracle no more crappy lifter sounds at first just smooth. I changed the oil today into a 5 gallon bucket it reeked of gas heavily. This car is a 2014 with 14,000 miles only so age can do it too and it had an incredible one owner maintenance record by date every year and through 45k Audi services. They did 45k service at 11k miles. It was just inspected by Audi Miami before I bought it too and they also missed an obvious severe case of 1k/3k vibration. Hoping no engine damage this stuff could go years without people knowing it. Had two cars with this problem and both had zero codes or signs externally.


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Would you say now: if you have gas or a smell in your engine oil, it’s likely a fault of a failing HPFP?

Glad you got it sorted out!


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[S6Man4.0tt]

Would you say now: if you have gas or a smell in your engine oil, it’s likely a fault of a failing HPFP?

Glad you got it sorted out!


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It's more commonly the fuel pumps and sometimes injectors stuck open or both like it says in this thread. That's how it appears from what I've seen. The pumps fault easily it's something to do with the cam driven/spring driven design that goes bad easily. I forgot to mention there was only 1100 miles on the oil I changed as well and it was as black as tar. I also did a BG flush before I put that oil in so I was surprised it looked like that as well. I would imagine the gas was in the oil was loosening carbon as well as it's a powerful solvent. Glad to get it out of there. Just went and romped on the car for a while. Can't tell much of a difference about anything performance wise. It still smells bad under the oil cap but I can tell it's reduced. I'm guessing it will take some time for the smell to go away fully. Hopefully this is the end of it.

[AudiA72011]

It's more commonly the fuel pumps and sometimes injectors stuck open or both like it says in this thread. That's how it appears from what I've seen. The pumps fault easily it's something to do with the cam driven/spring driven design that goes bad easily. I forgot to mention there was only 1100 miles on the oil I changed as well and it was as black as tar. I also did a BG flush before I put that oil in so I was surprised it looked like that as well. I would imagine the gas was in the oil was loosening carbon as well as it's a powerful solvent. Glad to get it out of there. Just went and romped on the car for a while. Can't tell much of a difference about anything performance wise. It still smells bad under the oil cap but I can tell it's reduced. I'm guessing it will take some time for the smell to go away fully. Hopefully this is the end of it.

Yeah and i think thats why i still smell a little fuel on the oil cap. Fuel has a strong smell and its hard to remove that smell just like that.

[wes8398]

A while later, but I just wanted to say thanks for the info in this thread, everyone. Very helpful. Well, all but this idiot's "contribution" lol

Is this a serious thread???? You smell gas in your oil...? You mean the same oil that mixes with gas on every single combustion stroke of your 4 stroke V8 engine? Over the course of your 3-5K mile oil change interval? Jesus Christ...

[dweep]

So I got an Audi RS6 for 2 weeks now and when I open the oil cap it really smells like gasoline. The car nest oil service is in october this year... Can I check the HPFP somehow or?

[MattyMarkey]

So I got an Audi RS6 for 2 weeks now and when I open the oil cap it really smells like gasoline. The car nest oil service is in october this year... Can I check the HPFP somehow or?

I haven’t done it, but I do believe there is a way to log fuel rail pressures with VCDS, which could/should indicate a failing HPFP


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[dweep]

My oil in MMI drops really fast. So I read about failing hpfp and pcv valve. I hope its the hpfp because I can replace them myself. Anyone an idea on this? I got high oil usage and smell gasoline in my oil cap.

[THCarpenter]

My oil in MMI drops really fast. So I read about failing hpfp and pcv valve. I hope its the hpfp because I can replace them myself. Anyone an idea on this? I got high oil usage and smell gasoline in my oil cap.

if you can DIY your HPFP, you can DIY your PCV

[ItsLarryG]

I don't know, the PCV is way more work and wouldn't want anyone thinking they are comparable. If you trust yourself to do the HPFP, the PCV should be doable as well, just a bunch more work.

[dweep]

I'm not sure about the PCV, anyone a part number for that to see what it costs here in Netherlands?
My problem seems related to hpfp but people say then oil needs to increase and not decrease because you get gasoline in the oil.

[THCarpenter]

I'm not sure about the PCV, anyone a part number for that to see what it costs here in Netherlands?
My problem seems related to hpfp but people say then oil needs to increase and not decrease because you get gasoline in the oil.

I know this is ECS, and FCPEuro in the US, but maybe you can use the part numbers to reference for your own research over yonder. I tried to look up on AWH-Shop but no luck
https://www.ecstuning.com/Audi-C7_S6...Emissions/PCV/
https://www.fcpeuro.com/Audi-parts/S...=&keywords=PCV

Audi/VW Part Number
Crankcase Vent Valve - 079103704N
Oil Separator Assembly - 079103542E
Crankcase Vent Valve Gasket - 079103161Q

[dweep]

Thanks @THCarpenter Only need to find out if its hpfp or pcv valve which is causing my gasoline smell in my oil